diff --git a/examples/000-CatchMain.cpp b/examples/000-CatchMain.cpp
index 0580b932..5d06bd98 100644
--- a/examples/000-CatchMain.cpp
+++ b/examples/000-CatchMain.cpp
@@ -4,7 +4,7 @@
 // of a testing binary, and other test files to link against it.
 
 // Let Catch provide main():
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 
 // That's it
 
diff --git a/examples/010-TestCase.cpp b/examples/010-TestCase.cpp
index 8eaa1c0e..d9939958 100644
--- a/examples/010-TestCase.cpp
+++ b/examples/010-TestCase.cpp
@@ -1,7 +1,7 @@
 // 010-TestCase.cpp
 
 // Let Catch provide main():
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 
 // And write tests in the same file:
 #include <catch2/catch_test_macros.hpp>
diff --git a/examples/020-TestCase-1.cpp b/examples/020-TestCase-1.cpp
index c734d029..5d17016a 100644
--- a/examples/020-TestCase-1.cpp
+++ b/examples/020-TestCase-1.cpp
@@ -4,7 +4,7 @@
 // source code of Catch itself and reuse the resulting object file for linking.
 
 // Let Catch provide main():
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 
 #include <catch2/catch_test_macros.hpp>
 
diff --git a/examples/231-Cfg-OutputStreams.cpp b/examples/231-Cfg-OutputStreams.cpp
index 6c97d1be..d0c1a632 100644
--- a/examples/231-Cfg-OutputStreams.cpp
+++ b/examples/231-Cfg-OutputStreams.cpp
@@ -6,7 +6,7 @@
 // there is no important difference between having `std::cerr` buffered
 // or unbuffered.
 
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 
 #include <catch2/catch_test_macros.hpp>
 
diff --git a/examples/300-Gen-OwnGenerator.cpp b/examples/300-Gen-OwnGenerator.cpp
index ec98a048..bff62907 100644
--- a/examples/300-Gen-OwnGenerator.cpp
+++ b/examples/300-Gen-OwnGenerator.cpp
@@ -5,8 +5,8 @@
 // It will have infinite capacity and settable lower/upper bound
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_generators.hpp>
-#include <catch2/catch_generators_generic.hpp>
+#include <catch2/generators/catch_generators.hpp>
+#include <catch2/generators/catch_generators_adapters.hpp>
 
 #include <random>
 
diff --git a/examples/301-Gen-MapTypeConversion.cpp b/examples/301-Gen-MapTypeConversion.cpp
index 425da347..15b90fdd 100644
--- a/examples/301-Gen-MapTypeConversion.cpp
+++ b/examples/301-Gen-MapTypeConversion.cpp
@@ -3,7 +3,7 @@
 
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_generators_generic.hpp>
+#include <catch2/generators/catch_generators_adapters.hpp>
 
 #include <string>
 #include <sstream>
diff --git a/examples/310-Gen-VariablesInGenerators.cpp b/examples/310-Gen-VariablesInGenerators.cpp
index 3fb089e8..0339c5f1 100644
--- a/examples/310-Gen-VariablesInGenerators.cpp
+++ b/examples/310-Gen-VariablesInGenerators.cpp
@@ -7,8 +7,8 @@
 // by value directly, or copied by the generators during construction.
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_generators_generic.hpp>
-#include <catch2/catch_generators_specific.hpp>
+#include <catch2/generators/catch_generators_adapters.hpp>
+#include <catch2/generators/catch_generators_random.hpp>
 
 TEST_CASE("Generate random doubles across different ranges",
           "[generator][example][advanced]") {
diff --git a/examples/311-Gen-CustomCapture.cpp b/examples/311-Gen-CustomCapture.cpp
index 35de7afc..13a7eab3 100644
--- a/examples/311-Gen-CustomCapture.cpp
+++ b/examples/311-Gen-CustomCapture.cpp
@@ -10,8 +10,8 @@
 // that.
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_generators_generic.hpp>
-#include <catch2/catch_generators_specific.hpp>
+#include <catch2/generators/catch_generators_adapters.hpp>
+#include <catch2/generators/catch_generators_random.hpp>
 
 TEST_CASE("Generate random doubles across different ranges",
           "[generator][example][advanced]") {
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index a1f57c7c..4693b5fc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -33,44 +33,46 @@ set(BENCHMARK_SOURCES
 SOURCE_GROUP("benchmark" FILES ${BENCHMARK_HEADERS} ${BENCHMARK_SOURCES})
 
 set(INTERNAL_HEADERS
-    ${SOURCES_DIR}/internal/catch_capture_matchers.h
+    ${SOURCES_DIR}/internal/catch_capture_matchers.hpp
     ${SOURCES_DIR}/internal/catch_container_nonmembers.hpp
-    ${SOURCES_DIR}/catch_approx.h
-    ${SOURCES_DIR}/catch_assertionhandler.h
-    ${SOURCES_DIR}/catch_assertioninfo.h
-    ${SOURCES_DIR}/catch_assertionresult.h
-    ${SOURCES_DIR}/catch_capture.hpp
-    ${SOURCES_DIR}/catch_clara.h
-    ${SOURCES_DIR}/catch_commandline.h
-    ${SOURCES_DIR}/catch_common.h
-    ${SOURCES_DIR}/catch_compiler_capabilities.h
+    ${SOURCES_DIR}/catch_approx.hpp
+    ${SOURCES_DIR}/internal/catch_assertionhandler.hpp
+    ${SOURCES_DIR}/catch_assertion_info.hpp
+    ${SOURCES_DIR}/catch_assertion_result.hpp
+    ${SOURCES_DIR}/internal/catch_capture.hpp
+    ${SOURCES_DIR}/internal/catch_clara.hpp
+    ${SOURCES_DIR}/internal/catch_commandline.hpp
+    ${SOURCES_DIR}/internal/catch_common.hpp
+    ${SOURCES_DIR}/internal/catch_compiler_capabilities.hpp
     ${SOURCES_DIR}/catch_config.hpp
-    ${SOURCES_DIR}/catch_console_colour.h
-    ${SOURCES_DIR}/catch_context.h
-    ${SOURCES_DIR}/catch_debug_console.h
-    ${SOURCES_DIR}/catch_debugger.h
-    ${SOURCES_DIR}/catch_decomposer.h
-    ${SOURCES_DIR}/catch_default_main.hpp
-    ${SOURCES_DIR}/catch_enforce.h
-    ${SOURCES_DIR}/catch_enum_values_registry.h
-    ${SOURCES_DIR}/catch_errno_guard.h
-    ${SOURCES_DIR}/catch_exception_translator_registry.h
-    ${SOURCES_DIR}/catch_fatal_condition.h
-    ${SOURCES_DIR}/catch_generator_exception.hpp
-    ${SOURCES_DIR}/catch_generators.hpp
-    ${SOURCES_DIR}/catch_generators_generic.hpp
-    ${SOURCES_DIR}/catch_generators_specific.hpp
-    ${SOURCES_DIR}/catch_interfaces_capture.h
-    ${SOURCES_DIR}/catch_interfaces_config.h
-    ${SOURCES_DIR}/catch_interfaces_enum_values_registry.h
-    ${SOURCES_DIR}/catch_interfaces_exception.h
-    ${SOURCES_DIR}/catch_interfaces_registry_hub.h
-    ${SOURCES_DIR}/catch_interfaces_reporter.h
-    ${SOURCES_DIR}/catch_interfaces_runner.h
-    ${SOURCES_DIR}/catch_interfaces_tag_alias_registry.h
-    ${SOURCES_DIR}/catch_interfaces_testcase.h
-    ${SOURCES_DIR}/catch_leak_detector.h
-    ${SOURCES_DIR}/catch_list.h
+    ${SOURCES_DIR}/internal/catch_console_colour.hpp
+    ${SOURCES_DIR}/internal/catch_context.hpp
+    ${SOURCES_DIR}/internal/catch_debug_console.hpp
+    ${SOURCES_DIR}/internal/catch_debugger.hpp
+    ${SOURCES_DIR}/internal/catch_decomposer.hpp
+    ${SOURCES_DIR}/internal/catch_default_main.hpp
+    ${SOURCES_DIR}/internal/catch_enforce.hpp
+    ${SOURCES_DIR}/internal/catch_enum_values_registry.hpp
+    ${SOURCES_DIR}/internal/catch_errno_guard.hpp
+    ${SOURCES_DIR}/internal/catch_exception_translator_registry.hpp
+    ${SOURCES_DIR}/internal/catch_fatal_condition.hpp
+    ${SOURCES_DIR}/generators/catch_generator_exception.hpp
+    ${SOURCES_DIR}/generators/catch_generators.hpp
+    ${SOURCES_DIR}/generators/catch_generators_adapters.hpp
+    ${SOURCES_DIR}/generators/catch_generators_random.hpp
+    ${SOURCES_DIR}/generators/catch_generators_range.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_capture.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_config.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_enum_values_registry.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_exception.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_generatortracker.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_registry_hub.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_reporter.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_runner.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_tag_alias_registry.hpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_testcase.hpp
+    ${SOURCES_DIR}/internal/catch_leak_detector.hpp
+    ${SOURCES_DIR}/internal/catch_list.hpp
     ${SOURCES_DIR}/matchers/catch_matchers.hpp
     ${SOURCES_DIR}/matchers/catch_matchers_container_properties.hpp
     ${SOURCES_DIR}/matchers/catch_matchers_contains.hpp
@@ -80,79 +82,79 @@ set(INTERNAL_HEADERS
     ${SOURCES_DIR}/matchers/catch_matchers_string.hpp
     ${SOURCES_DIR}/matchers/catch_matchers_templated.hpp
     ${SOURCES_DIR}/matchers/catch_matchers_vector.hpp
-    ${SOURCES_DIR}/catch_message.h
-    ${SOURCES_DIR}/catch_meta.hpp
+    ${SOURCES_DIR}/catch_message.hpp
+    ${SOURCES_DIR}/internal/catch_meta.hpp
     ${SOURCES_DIR}/catch_objc.hpp
     ${SOURCES_DIR}/catch_objc_arc.hpp
-    ${SOURCES_DIR}/catch_option.hpp
-    ${SOURCES_DIR}/catch_output_redirect.h
-    ${SOURCES_DIR}/catch_platform.h
-    ${SOURCES_DIR}/catch_polyfills.hpp
-    ${SOURCES_DIR}/catch_preprocessor.hpp
-    ${SOURCES_DIR}/catch_random_number_generator.h
+    ${SOURCES_DIR}/internal/catch_option.hpp
+    ${SOURCES_DIR}/internal/catch_output_redirect.hpp
+    ${SOURCES_DIR}/internal/catch_platform.hpp
+    ${SOURCES_DIR}/internal/catch_polyfills.hpp
+    ${SOURCES_DIR}/internal/catch_preprocessor.hpp
+    ${SOURCES_DIR}/internal/catch_random_number_generator.hpp
     ${SOURCES_DIR}/catch_reporter_registrars.hpp
-    ${SOURCES_DIR}/catch_reporter_registry.h
-    ${SOURCES_DIR}/catch_result_type.h
-    ${SOURCES_DIR}/catch_run_context.h
-    ${SOURCES_DIR}/catch_section.h
-    ${SOURCES_DIR}/catch_section_info.h
-    ${SOURCES_DIR}/catch_session.h
-    ${SOURCES_DIR}/catch_singletons.hpp
-    ${SOURCES_DIR}/catch_startup_exception_registry.h
-    ${SOURCES_DIR}/catch_stream.h
-    ${SOURCES_DIR}/catch_stringref.h
-    ${SOURCES_DIR}/catch_string_manip.h
-    ${SOURCES_DIR}/catch_tag_alias.h
-    ${SOURCES_DIR}/catch_tag_alias_autoregistrar.h
-    ${SOURCES_DIR}/catch_tag_alias_registry.h
-    ${SOURCES_DIR}/catch_test_case_info.h
-    ${SOURCES_DIR}/catch_test_case_registry_impl.h
-    ${SOURCES_DIR}/catch_test_case_tracker.h
+    ${SOURCES_DIR}/internal/catch_reporter_registry.hpp
+    ${SOURCES_DIR}/internal/catch_result_type.hpp
+    ${SOURCES_DIR}/internal/catch_run_context.hpp
+    ${SOURCES_DIR}/internal/catch_section.hpp
+    ${SOURCES_DIR}/catch_section_info.hpp
+    ${SOURCES_DIR}/catch_session.hpp
+    ${SOURCES_DIR}/internal/catch_singletons.hpp
+    ${SOURCES_DIR}/internal/catch_startup_exception_registry.hpp
+    ${SOURCES_DIR}/internal/catch_stream.hpp
+    ${SOURCES_DIR}/catch_stringref.hpp
+    ${SOURCES_DIR}/internal/catch_string_manip.hpp
+    ${SOURCES_DIR}/catch_tag_alias.hpp
+    ${SOURCES_DIR}/catch_tag_alias_autoregistrar.hpp
+    ${SOURCES_DIR}/internal/catch_tag_alias_registry.hpp
+    ${SOURCES_DIR}/catch_test_case_info.hpp
+    ${SOURCES_DIR}/internal/catch_test_case_registry_impl.hpp
+    ${SOURCES_DIR}/internal/catch_test_case_tracker.hpp
     ${SOURCES_DIR}/catch_test_macros.hpp
-    ${SOURCES_DIR}/catch_test_registry.h
-    ${SOURCES_DIR}/catch_test_spec.h
-    ${SOURCES_DIR}/catch_test_spec_parser.h
-    ${SOURCES_DIR}/catch_text.h
-    ${SOURCES_DIR}/catch_timer.h
-    ${SOURCES_DIR}/catch_to_string.hpp
-    ${SOURCES_DIR}/catch_tostring.h
-    ${SOURCES_DIR}/catch_totals.h
-    ${SOURCES_DIR}/catch_uncaught_exceptions.h
-    ${SOURCES_DIR}/catch_version.h
+    ${SOURCES_DIR}/internal/catch_test_registry.hpp
+    ${SOURCES_DIR}/catch_test_spec.hpp
+    ${SOURCES_DIR}/internal/catch_test_spec_parser.hpp
+    ${SOURCES_DIR}/internal/catch_text.hpp
+    ${SOURCES_DIR}/catch_timer.hpp
+    ${SOURCES_DIR}/internal/catch_to_string.hpp
+    ${SOURCES_DIR}/catch_tostring.hpp
+    ${SOURCES_DIR}/catch_totals.hpp
+    ${SOURCES_DIR}/internal/catch_uncaught_exceptions.hpp
+    ${SOURCES_DIR}/catch_version.hpp
     ${SOURCES_DIR}/catch_version_macros.hpp
-    ${SOURCES_DIR}/catch_wildcard_pattern.h
-    ${SOURCES_DIR}/catch_windows_h_proxy.h
-    ${SOURCES_DIR}/catch_xmlwriter.h
+    ${SOURCES_DIR}/internal/catch_wildcard_pattern.hpp
+    ${SOURCES_DIR}/internal/catch_windows_h_proxy.hpp
+    ${SOURCES_DIR}/internal/catch_xmlwriter.hpp
 )
 set(IMPL_SOURCES
     ${SOURCES_DIR}/catch_approx.cpp
-    ${SOURCES_DIR}/catch_assertionhandler.cpp
-    ${SOURCES_DIR}/catch_assertionresult.cpp
+    ${SOURCES_DIR}/internal/catch_assertionhandler.cpp
+    ${SOURCES_DIR}/catch_assertion_result.cpp
     ${SOURCES_DIR}/internal/catch_capture_matchers.cpp
-    ${SOURCES_DIR}/catch_commandline.cpp
-    ${SOURCES_DIR}/catch_common.cpp
+    ${SOURCES_DIR}/internal/catch_commandline.cpp
+    ${SOURCES_DIR}/internal/catch_common.cpp
     ${SOURCES_DIR}/catch_config.cpp
-    ${SOURCES_DIR}/catch_console_colour.cpp
-    ${SOURCES_DIR}/catch_context.cpp
-    ${SOURCES_DIR}/catch_debug_console.cpp
-    ${SOURCES_DIR}/catch_debugger.cpp
-    ${SOURCES_DIR}/catch_decomposer.cpp
-    ${SOURCES_DIR}/catch_enforce.cpp
-    ${SOURCES_DIR}/catch_enum_values_registry.cpp
-    ${SOURCES_DIR}/catch_errno_guard.cpp
-    ${SOURCES_DIR}/catch_exception_translator_registry.cpp
-    ${SOURCES_DIR}/catch_fatal_condition.cpp
-    ${SOURCES_DIR}/catch_generator_exception.cpp
-    ${SOURCES_DIR}/catch_generators.cpp
-    ${SOURCES_DIR}/catch_interfaces_capture.cpp
-    ${SOURCES_DIR}/catch_interfaces_config.cpp
-    ${SOURCES_DIR}/catch_interfaces_exception.cpp
-    ${SOURCES_DIR}/catch_interfaces_generatortracker.h
-    ${SOURCES_DIR}/catch_interfaces_registry_hub.cpp
-    ${SOURCES_DIR}/catch_interfaces_runner.cpp
-    ${SOURCES_DIR}/catch_interfaces_testcase.cpp
-    ${SOURCES_DIR}/catch_list.cpp
-    ${SOURCES_DIR}/catch_leak_detector.cpp
+    ${SOURCES_DIR}/internal/catch_console_colour.cpp
+    ${SOURCES_DIR}/internal/catch_context.cpp
+    ${SOURCES_DIR}/internal/catch_debug_console.cpp
+    ${SOURCES_DIR}/internal/catch_debugger.cpp
+    ${SOURCES_DIR}/internal/catch_decomposer.cpp
+    ${SOURCES_DIR}/internal/catch_enforce.cpp
+    ${SOURCES_DIR}/internal/catch_enum_values_registry.cpp
+    ${SOURCES_DIR}/internal/catch_errno_guard.cpp
+    ${SOURCES_DIR}/internal/catch_exception_translator_registry.cpp
+    ${SOURCES_DIR}/internal/catch_fatal_condition.cpp
+    ${SOURCES_DIR}/generators/catch_generator_exception.cpp
+    ${SOURCES_DIR}/generators/catch_generators.cpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_capture.cpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_config.cpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_exception.cpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_registry_hub.cpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_reporter.cpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_runner.cpp
+    ${SOURCES_DIR}/interfaces/catch_interfaces_testcase.cpp
+    ${SOURCES_DIR}/internal/catch_list.cpp
+    ${SOURCES_DIR}/internal/catch_leak_detector.cpp
     ${SOURCES_DIR}/matchers/catch_matchers.cpp
     ${SOURCES_DIR}/matchers/catch_matchers_container_properties.cpp
     ${SOURCES_DIR}/matchers/catch_matchers_exception.cpp
@@ -161,37 +163,36 @@ set(IMPL_SOURCES
     ${SOURCES_DIR}/matchers/catch_matchers_string.cpp
     ${SOURCES_DIR}/matchers/catch_matchers_templated.cpp
     ${SOURCES_DIR}/catch_message.cpp
-    ${SOURCES_DIR}/catch_output_redirect.cpp
+    ${SOURCES_DIR}/internal/catch_output_redirect.cpp
     ${SOURCES_DIR}/catch_registry_hub.cpp
-    ${SOURCES_DIR}/catch_interfaces_reporter.cpp
-    ${SOURCES_DIR}/catch_polyfills.cpp
-    ${SOURCES_DIR}/catch_random_number_generator.cpp
-    ${SOURCES_DIR}/catch_reporter_registry.cpp
-    ${SOURCES_DIR}/catch_result_type.cpp
-    ${SOURCES_DIR}/catch_run_context.cpp
-    ${SOURCES_DIR}/catch_section.cpp
+    ${SOURCES_DIR}/internal/catch_polyfills.cpp
+    ${SOURCES_DIR}/internal/catch_random_number_generator.cpp
+    ${SOURCES_DIR}/internal/catch_reporter_registry.cpp
+    ${SOURCES_DIR}/internal/catch_result_type.cpp
+    ${SOURCES_DIR}/internal/catch_run_context.cpp
+    ${SOURCES_DIR}/internal/catch_section.cpp
     ${SOURCES_DIR}/catch_session.cpp
-    ${SOURCES_DIR}/catch_singletons.cpp
-    ${SOURCES_DIR}/catch_startup_exception_registry.cpp
-    ${SOURCES_DIR}/catch_stream.cpp
-    ${SOURCES_DIR}/catch_stringref.cpp
-    ${SOURCES_DIR}/catch_string_manip.cpp
+    ${SOURCES_DIR}/internal/catch_singletons.cpp
+    ${SOURCES_DIR}/internal/catch_startup_exception_registry.cpp
+    ${SOURCES_DIR}/internal/catch_stream.cpp
+    ${SOURCES_DIR}/internal/catch_stringref.cpp
+    ${SOURCES_DIR}/internal/catch_string_manip.cpp
     ${SOURCES_DIR}/catch_tag_alias.cpp
     ${SOURCES_DIR}/catch_tag_alias_autoregistrar.cpp
-    ${SOURCES_DIR}/catch_tag_alias_registry.cpp
+    ${SOURCES_DIR}/internal/catch_tag_alias_registry.cpp
     ${SOURCES_DIR}/catch_test_case_info.cpp
-    ${SOURCES_DIR}/catch_test_case_registry_impl.cpp
-    ${SOURCES_DIR}/catch_test_case_tracker.cpp
-    ${SOURCES_DIR}/catch_test_registry.cpp
+    ${SOURCES_DIR}/internal/catch_test_case_registry_impl.cpp
+    ${SOURCES_DIR}/internal/catch_test_case_tracker.cpp
+    ${SOURCES_DIR}/internal/catch_test_registry.cpp
     ${SOURCES_DIR}/catch_test_spec.cpp
-    ${SOURCES_DIR}/catch_test_spec_parser.cpp
+    ${SOURCES_DIR}/internal/catch_test_spec_parser.cpp
     ${SOURCES_DIR}/catch_timer.cpp
     ${SOURCES_DIR}/catch_tostring.cpp
     ${SOURCES_DIR}/catch_totals.cpp
-    ${SOURCES_DIR}/catch_uncaught_exceptions.cpp
+    ${SOURCES_DIR}/internal/catch_uncaught_exceptions.cpp
     ${SOURCES_DIR}/catch_version.cpp
-    ${SOURCES_DIR}/catch_wildcard_pattern.cpp
-    ${SOURCES_DIR}/catch_xmlwriter.cpp
+    ${SOURCES_DIR}/internal/catch_wildcard_pattern.cpp
+    ${SOURCES_DIR}/internal/catch_xmlwriter.cpp
 )
 set(INTERNAL_FILES ${IMPL_SOURCES} ${INTERNAL_HEADERS})
 CheckFileList(INTERNAL_FILES ${SOURCES_DIR}/internal)
@@ -270,7 +271,7 @@ target_include_directories(Catch2
 
 
 add_library(Catch2Main STATIC
-    ${SOURCES_DIR}/catch_main.cpp
+    ${SOURCES_DIR}/internal/catch_main.cpp
 )
 add_library(Catch2::Catch2Main ALIAS Catch2Main)
 target_link_libraries(Catch2Main PUBLIC Catch2)
diff --git a/src/catch2/benchmark/catch_benchmark.hpp b/src/catch2/benchmark/catch_benchmark.hpp
index 154105c5..fe9866d6 100644
--- a/src/catch2/benchmark/catch_benchmark.hpp
+++ b/src/catch2/benchmark/catch_benchmark.hpp
@@ -11,9 +11,8 @@
 #define TWOBLUECUBES_CATCH_BENCHMARK_HPP_INCLUDED
 
 #include <catch2/catch_config.hpp>
-#include <catch2/catch_context.h>
-#include <catch2/catch_interfaces_reporter.h>
-#include <catch2/catch_test_registry.h>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
 
 #include <catch2/benchmark/catch_chronometer.hpp>
 #include <catch2/benchmark/catch_clock.hpp>
diff --git a/src/catch2/benchmark/catch_chronometer.hpp b/src/catch2/benchmark/catch_chronometer.hpp
index e150d20d..12dcee00 100644
--- a/src/catch2/benchmark/catch_chronometer.hpp
+++ b/src/catch2/benchmark/catch_chronometer.hpp
@@ -14,7 +14,7 @@
 #include <catch2/benchmark/catch_clock.hpp>
 #include <catch2/benchmark/catch_optimizer.hpp>
 #include <catch2/benchmark/detail/catch_complete_invoke.hpp>
-#include <catch2/catch_meta.hpp>
+#include <catch2/internal/catch_meta.hpp>
 
 namespace Catch {
     namespace Benchmark {
diff --git a/src/catch2/benchmark/detail/catch_benchmark_function.hpp b/src/catch2/benchmark/detail/catch_benchmark_function.hpp
index 4fd86896..5e86a154 100644
--- a/src/catch2/benchmark/detail/catch_benchmark_function.hpp
+++ b/src/catch2/benchmark/detail/catch_benchmark_function.hpp
@@ -13,7 +13,7 @@
 
 #include <catch2/benchmark/catch_chronometer.hpp>
 #include <catch2/benchmark/detail/catch_complete_invoke.hpp>
-#include <catch2/catch_meta.hpp>
+#include <catch2/internal/catch_meta.hpp>
 
 #include <cassert>
 #include <type_traits>
diff --git a/src/catch2/benchmark/detail/catch_complete_invoke.hpp b/src/catch2/benchmark/detail/catch_complete_invoke.hpp
index 497e0b3f..d6dc2e9d 100644
--- a/src/catch2/benchmark/detail/catch_complete_invoke.hpp
+++ b/src/catch2/benchmark/detail/catch_complete_invoke.hpp
@@ -11,9 +11,9 @@
 #ifndef TWOBLUECUBES_CATCH_DETAIL_COMPLETE_INVOKE_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_DETAIL_COMPLETE_INVOKE_HPP_INCLUDED
 
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_interfaces_capture.h>
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 #include <type_traits>
 #include <utility>
diff --git a/src/catch2/benchmark/detail/catch_run_for_at_least.cpp b/src/catch2/benchmark/detail/catch_run_for_at_least.cpp
index 89c1e749..f1dcbaba 100644
--- a/src/catch2/benchmark/detail/catch_run_for_at_least.cpp
+++ b/src/catch2/benchmark/detail/catch_run_for_at_least.cpp
@@ -7,7 +7,7 @@
 #include <catch2/benchmark/detail/catch_run_for_at_least.hpp>
 
 #include <exception>
-#include <catch2/catch_enforce.h>
+#include <catch2/internal/catch_enforce.hpp>
 
 namespace Catch {
     namespace Benchmark {
diff --git a/src/catch2/benchmark/detail/catch_run_for_at_least.hpp b/src/catch2/benchmark/detail/catch_run_for_at_least.hpp
index 325e5227..ee5510d6 100644
--- a/src/catch2/benchmark/detail/catch_run_for_at_least.hpp
+++ b/src/catch2/benchmark/detail/catch_run_for_at_least.hpp
@@ -16,7 +16,7 @@
 #include <catch2/benchmark/detail/catch_measure.hpp>
 #include <catch2/benchmark/detail/catch_complete_invoke.hpp>
 #include <catch2/benchmark/detail/catch_timing.hpp>
-#include <catch2/catch_meta.hpp>
+#include <catch2/internal/catch_meta.hpp>
 
 #include <utility>
 #include <type_traits>
diff --git a/src/catch2/benchmark/detail/catch_stats.cpp b/src/catch2/benchmark/detail/catch_stats.cpp
index 5aacce01..11ca81b4 100644
--- a/src/catch2/benchmark/detail/catch_stats.cpp
+++ b/src/catch2/benchmark/detail/catch_stats.cpp
@@ -10,7 +10,7 @@
 
 #include <catch2/benchmark/detail/catch_stats.hpp>
 
-#include <catch2/catch_compiler_capabilities.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
 
 #include <cassert>
 #include <random>
diff --git a/src/catch2/catch_approx.cpp b/src/catch2/catch_approx.cpp
index 4296e8d5..809d4824 100644
--- a/src/catch2/catch_approx.cpp
+++ b/src/catch2/catch_approx.cpp
@@ -6,8 +6,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_approx.h>
-#include <catch2/catch_enforce.h>
+#include <catch2/catch_approx.hpp>
+#include <catch2/internal/catch_enforce.hpp>
 
 #include <cmath>
 #include <limits>
diff --git a/src/catch2/catch_approx.h b/src/catch2/catch_approx.hpp
similarity index 96%
rename from src/catch2/catch_approx.h
rename to src/catch2/catch_approx.hpp
index 4f3a6958..e7be3c96 100644
--- a/src/catch2/catch_approx.h
+++ b/src/catch2/catch_approx.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED
 
-#include <catch2/catch_tostring.h>
+#include <catch2/catch_tostring.hpp>
 
 #include <type_traits>
 
@@ -17,9 +17,9 @@ namespace Catch {
     class Approx {
     private:
         bool equalityComparisonImpl(double other) const;
-        //! Sets and validates the new margin (margin >= 0)
+        // Sets and validates the new margin (margin >= 0)
         void setMargin(double margin);
-        //! Sets and validates the new epsilon (0 < epsilon < 1)
+        // Sets and validates the new epsilon (0 < epsilon < 1)
         void setEpsilon(double epsilon);
 
     public:
diff --git a/src/catch2/catch_assertioninfo.h b/src/catch2/catch_assertion_info.hpp
similarity index 84%
rename from src/catch2/catch_assertioninfo.h
rename to src/catch2/catch_assertion_info.hpp
index 37ea1d14..b05f4921 100644
--- a/src/catch2/catch_assertioninfo.h
+++ b/src/catch2/catch_assertion_info.hpp
@@ -8,9 +8,9 @@
 #ifndef TWOBLUECUBES_CATCH_ASSERTIONINFO_H_INCLUDED
 #define TWOBLUECUBES_CATCH_ASSERTIONINFO_H_INCLUDED
 
-#include <catch2/catch_result_type.h>
-#include <catch2/catch_common.h>
-#include <catch2/catch_stringref.h>
+#include <catch2/internal/catch_result_type.hpp>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/catch_stringref.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_assertionresult.cpp b/src/catch2/catch_assertion_result.cpp
similarity index 98%
rename from src/catch2/catch_assertionresult.cpp
rename to src/catch2/catch_assertion_result.cpp
index 2ec757f9..4bbf0416 100644
--- a/src/catch2/catch_assertionresult.cpp
+++ b/src/catch2/catch_assertion_result.cpp
@@ -6,7 +6,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_assertionresult.h>
+#include <catch2/catch_assertion_result.hpp>
 
 namespace Catch {
     AssertionResultData::AssertionResultData(ResultWas::OfType _resultType, LazyExpression const & _lazyExpression):
diff --git a/src/catch2/catch_assertionresult.h b/src/catch2/catch_assertion_result.hpp
similarity index 87%
rename from src/catch2/catch_assertionresult.h
rename to src/catch2/catch_assertion_result.hpp
index 37ef83a0..5b1029f3 100644
--- a/src/catch2/catch_assertionresult.h
+++ b/src/catch2/catch_assertion_result.hpp
@@ -9,11 +9,11 @@
 #define TWOBLUECUBES_CATCH_ASSERTIONRESULT_H_INCLUDED
 
 #include <string>
-#include <catch2/catch_assertioninfo.h>
-#include <catch2/catch_result_type.h>
-#include <catch2/catch_common.h>
-#include <catch2/catch_stringref.h>
-#include <catch2/catch_assertionhandler.h>
+#include <catch2/catch_assertion_info.hpp>
+#include <catch2/internal/catch_result_type.hpp>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/internal/catch_assertionhandler.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_config.cpp b/src/catch2/catch_config.cpp
index 7c0393da..263fb232 100644
--- a/src/catch2/catch_config.cpp
+++ b/src/catch2/catch_config.cpp
@@ -6,9 +6,11 @@
  */
 
 #include <catch2/catch_config.hpp>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_stringref.h>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/internal/catch_test_spec_parser.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_config.hpp b/src/catch2/catch_config.hpp
index 14972121..55cff0ee 100644
--- a/src/catch2/catch_config.hpp
+++ b/src/catch2/catch_config.hpp
@@ -8,8 +8,8 @@
 #ifndef TWOBLUECUBES_CATCH_CONFIG_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_CONFIG_HPP_INCLUDED
 
-#include <catch2/catch_test_spec_parser.h>
-#include <catch2/catch_interfaces_config.h>
+#include <catch2/catch_test_spec.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
 
 #include <memory>
 #include <vector>
diff --git a/src/catch2/catch_interfaces_config.cpp b/src/catch2/catch_interfaces_config.cpp
deleted file mode 100644
index b1f4238a..00000000
--- a/src/catch2/catch_interfaces_config.cpp
+++ /dev/null
@@ -1,5 +0,0 @@
-#include <catch2/catch_interfaces_config.h>
-
-namespace Catch {
-    IConfig::~IConfig() = default;
-}
diff --git a/src/catch2/catch_interfaces_runner.cpp b/src/catch2/catch_interfaces_runner.cpp
deleted file mode 100644
index 3b9df251..00000000
--- a/src/catch2/catch_interfaces_runner.cpp
+++ /dev/null
@@ -1,5 +0,0 @@
-#include <catch2/catch_interfaces_runner.h>
-
-namespace Catch {
-    IRunner::~IRunner() = default;
-}
diff --git a/src/catch2/catch_message.cpp b/src/catch2/catch_message.cpp
index 24cd789b..08207ee7 100644
--- a/src/catch2/catch_message.cpp
+++ b/src/catch2/catch_message.cpp
@@ -6,10 +6,10 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_message.h>
-#include <catch2/catch_interfaces_capture.h>
-#include <catch2/catch_uncaught_exceptions.h>
-#include <catch2/catch_enforce.h>
+#include <catch2/catch_message.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
+#include <catch2/internal/catch_uncaught_exceptions.hpp>
+#include <catch2/internal/catch_enforce.hpp>
 
 #include <cassert>
 #include <stack>
diff --git a/src/catch2/catch_message.h b/src/catch2/catch_message.hpp
similarity index 92%
rename from src/catch2/catch_message.h
rename to src/catch2/catch_message.hpp
index b27376b5..84f87dbb 100644
--- a/src/catch2/catch_message.h
+++ b/src/catch2/catch_message.hpp
@@ -8,11 +8,11 @@
 #ifndef TWOBLUECUBES_CATCH_MESSAGE_H_INCLUDED
 #define TWOBLUECUBES_CATCH_MESSAGE_H_INCLUDED
 
-#include <catch2/catch_result_type.h>
-#include <catch2/catch_common.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_interfaces_capture.h>
-#include <catch2/catch_tostring.h>
+#include <catch2/internal/catch_result_type.hpp>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
+#include <catch2/catch_tostring.hpp>
 
 #include <string>
 #include <vector>
diff --git a/src/catch2/catch_objc.hpp b/src/catch2/catch_objc.hpp
index 6484e321..72c14518 100644
--- a/src/catch2/catch_objc.hpp
+++ b/src/catch2/catch_objc.hpp
@@ -17,9 +17,9 @@
 // NB. Any general catch headers included here must be included
 // in catch.hpp first to make sure they are included by the single
 // header for non obj-usage
-#include <catch2/catch_test_case_info.h>
-#include <catch2/catch_string_manip.h>
-#include <catch2/catch_tostring.h>
+#include <catch2/catch_test_case_info.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/catch_tostring.hpp>
 
 ///////////////////////////////////////////////////////////////////////////////
 // This protocol is really only here for (self) documenting purposes, since
diff --git a/src/catch2/catch_registry_hub.cpp b/src/catch2/catch_registry_hub.cpp
index 8194c417..c6a19f09 100644
--- a/src/catch2/catch_registry_hub.cpp
+++ b/src/catch2/catch_registry_hub.cpp
@@ -6,16 +6,16 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
-#include <catch2/catch_context.h>
-#include <catch2/catch_test_case_registry_impl.h>
-#include <catch2/catch_reporter_registry.h>
-#include <catch2/catch_exception_translator_registry.h>
-#include <catch2/catch_tag_alias_registry.h>
-#include <catch2/catch_startup_exception_registry.h>
-#include <catch2/catch_singletons.hpp>
-#include <catch2/catch_enum_values_registry.h>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_test_case_registry_impl.hpp>
+#include <catch2/internal/catch_reporter_registry.hpp>
+#include <catch2/internal/catch_exception_translator_registry.hpp>
+#include <catch2/internal/catch_tag_alias_registry.hpp>
+#include <catch2/internal/catch_startup_exception_registry.hpp>
+#include <catch2/internal/catch_singletons.hpp>
+#include <catch2/internal/catch_enum_values_registry.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_reporter_registrars.hpp b/src/catch2/catch_reporter_registrars.hpp
index 4aecd518..a4b9efb5 100644
--- a/src/catch2/catch_reporter_registrars.hpp
+++ b/src/catch2/catch_reporter_registrars.hpp
@@ -9,7 +9,7 @@
 #ifndef TWOBLUECUBES_CATCH_REPORTER_REGISTRARS_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_REPORTER_REGISTRARS_HPP_INCLUDED
 
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_section_info.h b/src/catch2/catch_section_info.hpp
similarity index 90%
rename from src/catch2/catch_section_info.h
rename to src/catch2/catch_section_info.hpp
index ca06f79c..6c8edb53 100644
--- a/src/catch2/catch_section_info.h
+++ b/src/catch2/catch_section_info.hpp
@@ -8,9 +8,9 @@
 #ifndef TWOBLUECUBES_CATCH_SECTION_INFO_H_INCLUDED
 #define TWOBLUECUBES_CATCH_SECTION_INFO_H_INCLUDED
 
-#include <catch2/catch_common.h>
-#include <catch2/catch_stringref.h>
-#include <catch2/catch_totals.h>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/catch_totals.hpp>
 
 #include <string>
 
diff --git a/src/catch2/catch_session.cpp b/src/catch2/catch_session.cpp
index 01e4fd87..e85e0672 100644
--- a/src/catch2/catch_session.cpp
+++ b/src/catch2/catch_session.cpp
@@ -5,22 +5,21 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_session.h>
-#include <catch2/catch_commandline.h>
-#include <catch2/catch_console_colour.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_list.h>
-#include <catch2/catch_context.h>
-#include <catch2/catch_run_context.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_test_spec.h>
-#include <catch2/catch_version.h>
-#include <catch2/catch_interfaces_reporter.h>
-#include <catch2/catch_random_number_generator.h>
-#include <catch2/catch_startup_exception_registry.h>
-#include <catch2/catch_text.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_windows_h_proxy.h>
+#include <catch2/catch_session.hpp>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_list.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_run_context.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/catch_test_spec.hpp>
+#include <catch2/catch_version.hpp>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
+#include <catch2/internal/catch_random_number_generator.hpp>
+#include <catch2/internal/catch_startup_exception_registry.hpp>
+#include <catch2/internal/catch_text.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/internal/catch_windows_h_proxy.hpp>
 #include <catch2/reporters/catch_reporter_listening.hpp>
 
 #include <cstdlib>
diff --git a/src/catch2/catch_session.h b/src/catch2/catch_session.hpp
similarity index 94%
rename from src/catch2/catch_session.h
rename to src/catch2/catch_session.hpp
index abb9b062..e6269532 100644
--- a/src/catch2/catch_session.h
+++ b/src/catch2/catch_session.hpp
@@ -8,9 +8,9 @@
 #ifndef TWOBLUECUBES_CATCH_RUNNER_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_RUNNER_HPP_INCLUDED
 
-#include <catch2/catch_commandline.h>
+#include <catch2/internal/catch_commandline.hpp>
 #include <catch2/catch_config.hpp>
-#include <catch2/catch_text.h>
+#include <catch2/internal/catch_text.hpp>
 
 #include <memory>
 
diff --git a/src/catch2/catch_stringref.h b/src/catch2/catch_stringref.hpp
similarity index 100%
rename from src/catch2/catch_stringref.h
rename to src/catch2/catch_stringref.hpp
diff --git a/src/catch2/catch_tag_alias.cpp b/src/catch2/catch_tag_alias.cpp
index aa7d5393..5b7af537 100644
--- a/src/catch2/catch_tag_alias.cpp
+++ b/src/catch2/catch_tag_alias.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_tag_alias.h>
+#include <catch2/catch_tag_alias.hpp>
 
 namespace Catch {
     TagAlias::TagAlias(std::string const & _tag, SourceLineInfo _lineInfo): tag(_tag), lineInfo(_lineInfo) {}    
diff --git a/src/catch2/catch_tag_alias.h b/src/catch2/catch_tag_alias.hpp
similarity index 93%
rename from src/catch2/catch_tag_alias.h
rename to src/catch2/catch_tag_alias.hpp
index 01692ae6..37c7174b 100644
--- a/src/catch2/catch_tag_alias.h
+++ b/src/catch2/catch_tag_alias.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_TAG_ALIAS_H_INCLUDED
 #define TWOBLUECUBES_CATCH_TAG_ALIAS_H_INCLUDED
 
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_common.hpp>
 
 #include <string>
 
diff --git a/src/catch2/catch_tag_alias_autoregistrar.cpp b/src/catch2/catch_tag_alias_autoregistrar.cpp
index 6f09d083..ea0e27b0 100644
--- a/src/catch2/catch_tag_alias_autoregistrar.cpp
+++ b/src/catch2/catch_tag_alias_autoregistrar.cpp
@@ -1,6 +1,6 @@
-#include <catch2/catch_tag_alias_autoregistrar.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/catch_tag_alias_autoregistrar.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_tag_alias_autoregistrar.h b/src/catch2/catch_tag_alias_autoregistrar.hpp
similarity index 95%
rename from src/catch2/catch_tag_alias_autoregistrar.h
rename to src/catch2/catch_tag_alias_autoregistrar.hpp
index b104ace6..a201e997 100644
--- a/src/catch2/catch_tag_alias_autoregistrar.h
+++ b/src/catch2/catch_tag_alias_autoregistrar.hpp
@@ -7,7 +7,7 @@
 #ifndef TWOBLUECUBES_CATCH_TAG_ALIAS_AUTOREGISTRAR_H_INCLUDED
 #define TWOBLUECUBES_CATCH_TAG_ALIAS_AUTOREGISTRAR_H_INCLUDED
 
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_common.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_test_case_info.cpp b/src/catch2/catch_test_case_info.cpp
index c4e1416a..7be5b861 100644
--- a/src/catch2/catch_test_case_info.cpp
+++ b/src/catch2/catch_test_case_info.cpp
@@ -6,11 +6,11 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_test_case_info.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_test_spec.h>
-#include <catch2/catch_interfaces_testcase.h>
-#include <catch2/catch_string_manip.h>
+#include <catch2/catch_test_case_info.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/catch_test_spec.hpp>
+#include <catch2/interfaces/catch_interfaces_testcase.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 #include <cctype>
 #include <exception>
diff --git a/src/catch2/catch_test_case_info.h b/src/catch2/catch_test_case_info.hpp
similarity index 95%
rename from src/catch2/catch_test_case_info.h
rename to src/catch2/catch_test_case_info.hpp
index 540966e6..ccdaec67 100644
--- a/src/catch2/catch_test_case_info.h
+++ b/src/catch2/catch_test_case_info.hpp
@@ -8,9 +8,9 @@
 #ifndef TWOBLUECUBES_CATCH_TEST_CASE_INFO_H_INCLUDED
 #define TWOBLUECUBES_CATCH_TEST_CASE_INFO_H_INCLUDED
 
-#include <catch2/catch_common.h>
-#include <catch2/catch_stringref.h>
-#include <catch2/catch_test_registry.h>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/internal/catch_test_registry.hpp>
 
 #include <string>
 #include <vector>
diff --git a/src/catch2/catch_test_macros.hpp b/src/catch2/catch_test_macros.hpp
index a3159a3c..e323b396 100644
--- a/src/catch2/catch_test_macros.hpp
+++ b/src/catch2/catch_test_macros.hpp
@@ -6,11 +6,11 @@
 #ifndef TWOBLUECUBES_CATCH_TEST_MACROS_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_TEST_MACROS_HPP_INCLUDED
 
-#include <catch2/catch_capture.hpp>
-#include <catch2/catch_interfaces_exception.h>
-#include <catch2/catch_preprocessor.hpp>
-#include <catch2/catch_section.h>
-#include <catch2/catch_test_registry.h>
+#include <catch2/internal/catch_capture.hpp>
+#include <catch2/interfaces/catch_interfaces_exception.hpp>
+#include <catch2/internal/catch_preprocessor.hpp>
+#include <catch2/internal/catch_section.hpp>
+#include <catch2/internal/catch_test_registry.hpp>
 
 #if !defined(CATCH_CONFIG_DISABLE)
 //////
diff --git a/src/catch2/catch_test_spec.cpp b/src/catch2/catch_test_spec.cpp
index e3fd7f1b..87cf8cae 100644
--- a/src/catch2/catch_test_spec.cpp
+++ b/src/catch2/catch_test_spec.cpp
@@ -5,9 +5,10 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_test_spec.h>
-#include <catch2/catch_string_manip.h>
-#include <catch2/catch_interfaces_config.h>
+#include <catch2/catch_test_spec.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
+#include <catch2/catch_test_case_info.hpp>
 
 #include <algorithm>
 #include <string>
diff --git a/src/catch2/catch_test_spec.h b/src/catch2/catch_test_spec.hpp
similarity index 95%
rename from src/catch2/catch_test_spec.h
rename to src/catch2/catch_test_spec.hpp
index d18ec521..3a767c74 100644
--- a/src/catch2/catch_test_spec.h
+++ b/src/catch2/catch_test_spec.hpp
@@ -13,8 +13,7 @@
 #pragma clang diagnostic ignored "-Wpadded"
 #endif
 
-#include <catch2/catch_wildcard_pattern.h>
-#include <catch2/catch_test_case_info.h>
+#include <catch2/internal/catch_wildcard_pattern.hpp>
 
 #include <string>
 #include <vector>
@@ -23,6 +22,8 @@
 namespace Catch {
 
     struct IConfig;
+    struct TestCaseInfo;
+    class TestCaseHandle;
 
     class TestSpec {
 
diff --git a/src/catch2/catch_timer.cpp b/src/catch2/catch_timer.cpp
index a21b1834..84442bb2 100644
--- a/src/catch2/catch_timer.cpp
+++ b/src/catch2/catch_timer.cpp
@@ -6,7 +6,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_timer.h>
+#include <catch2/catch_timer.hpp>
 
 #include <chrono>
 
diff --git a/src/catch2/catch_timer.h b/src/catch2/catch_timer.hpp
similarity index 100%
rename from src/catch2/catch_timer.h
rename to src/catch2/catch_timer.hpp
diff --git a/src/catch2/catch_tostring.cpp b/src/catch2/catch_tostring.cpp
index 0e3abbde..3a63a598 100644
--- a/src/catch2/catch_tostring.cpp
+++ b/src/catch2/catch_tostring.cpp
@@ -13,10 +13,10 @@
 #endif
 
 
-#include <catch2/catch_tostring.h>
-#include <catch2/catch_interfaces_config.h>
-#include <catch2/catch_context.h>
-#include <catch2/catch_polyfills.hpp>
+#include <catch2/catch_tostring.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_polyfills.hpp>
 
 #include <cmath>
 #include <iomanip>
diff --git a/src/catch2/catch_tostring.h b/src/catch2/catch_tostring.hpp
similarity index 98%
rename from src/catch2/catch_tostring.h
rename to src/catch2/catch_tostring.hpp
index b5339688..1e0158b4 100644
--- a/src/catch2/catch_tostring.h
+++ b/src/catch2/catch_tostring.hpp
@@ -13,9 +13,9 @@
 #include <cstddef>
 #include <type_traits>
 #include <string>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_interfaces_enum_values_registry.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/interfaces/catch_interfaces_enum_values_registry.hpp>
 
 #ifdef CATCH_CONFIG_CPP17_STRING_VIEW
 #include <string_view>
@@ -648,7 +648,7 @@ struct ratio_string<std::milli> {
     };
 }
 
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 #define INTERNAL_CATCH_REGISTER_ENUM( enumName, ... ) \
 namespace Catch { \
diff --git a/src/catch2/catch_totals.cpp b/src/catch2/catch_totals.cpp
index 4ef05524..103610c4 100644
--- a/src/catch2/catch_totals.cpp
+++ b/src/catch2/catch_totals.cpp
@@ -5,7 +5,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_totals.h>
+#include <catch2/catch_totals.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_totals.h b/src/catch2/catch_totals.hpp
similarity index 100%
rename from src/catch2/catch_totals.h
rename to src/catch2/catch_totals.hpp
diff --git a/src/catch2/catch_version.cpp b/src/catch2/catch_version.cpp
index 64db9dbc..6e12e340 100644
--- a/src/catch2/catch_version.cpp
+++ b/src/catch2/catch_version.cpp
@@ -6,7 +6,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_version.h>
+#include <catch2/catch_version.hpp>
 #include <ostream>
 
 namespace Catch {
diff --git a/src/catch2/catch_version.h b/src/catch2/catch_version.hpp
similarity index 100%
rename from src/catch2/catch_version.h
rename to src/catch2/catch_version.hpp
diff --git a/src/catch2/catch_generator_exception.cpp b/src/catch2/generators/catch_generator_exception.cpp
similarity index 83%
rename from src/catch2/catch_generator_exception.cpp
rename to src/catch2/generators/catch_generator_exception.cpp
index 9ec5d55b..446c732a 100644
--- a/src/catch2/catch_generator_exception.cpp
+++ b/src/catch2/generators/catch_generator_exception.cpp
@@ -3,7 +3,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_generator_exception.hpp>
+#include <catch2/generators/catch_generator_exception.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_generator_exception.hpp b/src/catch2/generators/catch_generator_exception.hpp
similarity index 100%
rename from src/catch2/catch_generator_exception.hpp
rename to src/catch2/generators/catch_generator_exception.hpp
diff --git a/src/catch2/catch_generators.cpp b/src/catch2/generators/catch_generators.cpp
similarity index 78%
rename from src/catch2/catch_generators.cpp
rename to src/catch2/generators/catch_generators.cpp
index 48d98b92..d0c759c4 100644
--- a/src/catch2/catch_generators.cpp
+++ b/src/catch2/generators/catch_generators.cpp
@@ -5,10 +5,10 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_generators.hpp>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_generator_exception.hpp>
-#include <catch2/catch_interfaces_capture.h>
+#include <catch2/generators/catch_generators.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/generators/catch_generator_exception.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
 
 #include <limits>
 #include <set>
diff --git a/src/catch2/catch_generators.hpp b/src/catch2/generators/catch_generators.hpp
similarity index 98%
rename from src/catch2/catch_generators.hpp
rename to src/catch2/generators/catch_generators.hpp
index d49ae2e2..60ab4b4f 100644
--- a/src/catch2/catch_generators.hpp
+++ b/src/catch2/generators/catch_generators.hpp
@@ -7,8 +7,8 @@
 #ifndef TWOBLUECUBES_CATCH_GENERATORS_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_GENERATORS_HPP_INCLUDED
 
-#include <catch2/catch_interfaces_generatortracker.h>
-#include <catch2/catch_common.h>
+#include <catch2/interfaces/catch_interfaces_generatortracker.hpp>
+#include <catch2/internal/catch_common.hpp>
 
 #include <memory>
 #include <vector>
diff --git a/src/catch2/catch_generators_generic.hpp b/src/catch2/generators/catch_generators_adapters.hpp
similarity index 98%
rename from src/catch2/catch_generators_generic.hpp
rename to src/catch2/generators/catch_generators_adapters.hpp
index 954150b9..5a2ec54c 100644
--- a/src/catch2/catch_generators_generic.hpp
+++ b/src/catch2/generators/catch_generators_adapters.hpp
@@ -7,8 +7,8 @@
 #ifndef TWOBLUECUBES_CATCH_GENERATORS_GENERIC_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_GENERATORS_GENERIC_HPP_INCLUDED
 
-#include <catch2/catch_generators.hpp>
-#include <catch2/catch_meta.hpp>
+#include <catch2/generators/catch_generators.hpp>
+#include <catch2/internal/catch_meta.hpp>
 
 namespace Catch {
 namespace Generators {
diff --git a/src/catch2/generators/catch_generators_random.hpp b/src/catch2/generators/catch_generators_random.hpp
new file mode 100644
index 00000000..03cb57c1
--- /dev/null
+++ b/src/catch2/generators/catch_generators_random.hpp
@@ -0,0 +1,88 @@
+/*
+ *  Created by Martin on 15/6/2018.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+#ifndef TWOBLUECUBES_CATCH_GENERATORS_RANDOM_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_GENERATORS_RANDOM_HPP_INCLUDED
+
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/generators/catch_generators.hpp>
+#include <catch2/internal/catch_random_number_generator.hpp>
+
+#include <random>
+
+namespace Catch {
+namespace Generators {
+
+template <typename Float>
+class RandomFloatingGenerator final : public IGenerator<Float> {
+    Catch::SimplePcg32& m_rng;
+    std::uniform_real_distribution<Float> m_dist;
+    Float m_current_number;
+public:
+
+    RandomFloatingGenerator(Float a, Float b):
+        m_rng(rng()),
+        m_dist(a, b) {
+        static_cast<void>(next());
+    }
+
+    Float const& get() const override {
+        return m_current_number;
+    }
+    bool next() override {
+        m_current_number = m_dist(m_rng);
+        return true;
+    }
+};
+
+template <typename Integer>
+class RandomIntegerGenerator final : public IGenerator<Integer> {
+    Catch::SimplePcg32& m_rng;
+    std::uniform_int_distribution<Integer> m_dist;
+    Integer m_current_number;
+public:
+
+    RandomIntegerGenerator(Integer a, Integer b):
+        m_rng(rng()),
+        m_dist(a, b) {
+        static_cast<void>(next());
+    }
+
+    Integer const& get() const override {
+        return m_current_number;
+    }
+    bool next() override {
+        m_current_number = m_dist(m_rng);
+        return true;
+    }
+};
+
+// TODO: Ideally this would be also constrained against the various char types,
+//       but I don't expect users to run into that in practice.
+template <typename T>
+std::enable_if_t<std::is_integral<T>::value && !std::is_same<T, bool>::value,
+GeneratorWrapper<T>>
+random(T a, T b) {
+    return GeneratorWrapper<T>(
+        std::make_unique<RandomIntegerGenerator<T>>(a, b)
+    );
+}
+
+template <typename T>
+std::enable_if_t<std::is_floating_point<T>::value,
+GeneratorWrapper<T>>
+random(T a, T b) {
+    return GeneratorWrapper<T>(
+        std::make_unique<RandomFloatingGenerator<T>>(a, b)
+    );
+}
+
+
+} // namespace Generators
+} // namespace Catch
+
+
+#endif // TWOBLUECUBES_CATCH_GENERATORS_RANDOM_HPP_INCLUDED
diff --git a/src/catch2/catch_generators_specific.hpp b/src/catch2/generators/catch_generators_range.hpp
similarity index 61%
rename from src/catch2/catch_generators_specific.hpp
rename to src/catch2/generators/catch_generators_range.hpp
index f61a2be2..e2c5c522 100644
--- a/src/catch2/catch_generators_specific.hpp
+++ b/src/catch2/generators/catch_generators_range.hpp
@@ -4,83 +4,17 @@
  *  Distributed under the Boost Software License, Version 1.0. (See accompanying
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
-#ifndef TWOBLUECUBES_CATCH_GENERATORS_SPECIFIC_HPP_INCLUDED
-#define TWOBLUECUBES_CATCH_GENERATORS_SPECIFIC_HPP_INCLUDED
+#ifndef TWOBLUECUBES_CATCH_GENERATORS_RANGE_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_GENERATORS_RANGE_HPP_INCLUDED
 
-#include <catch2/catch_context.h>
-#include <catch2/catch_generators.hpp>
-#include <catch2/catch_interfaces_config.h>
-#include <catch2/catch_random_number_generator.h>
+#include <catch2/generators/catch_generators.hpp>
 
-#include <random>
+#include <iterator>
+#include <type_traits>
 
 namespace Catch {
 namespace Generators {
 
-template <typename Float>
-class RandomFloatingGenerator final : public IGenerator<Float> {
-    Catch::SimplePcg32& m_rng;
-    std::uniform_real_distribution<Float> m_dist;
-    Float m_current_number;
-public:
-
-    RandomFloatingGenerator(Float a, Float b):
-        m_rng(rng()),
-        m_dist(a, b) {
-        static_cast<void>(next());
-    }
-
-    Float const& get() const override {
-        return m_current_number;
-    }
-    bool next() override {
-        m_current_number = m_dist(m_rng);
-        return true;
-    }
-};
-
-template <typename Integer>
-class RandomIntegerGenerator final : public IGenerator<Integer> {
-    Catch::SimplePcg32& m_rng;
-    std::uniform_int_distribution<Integer> m_dist;
-    Integer m_current_number;
-public:
-
-    RandomIntegerGenerator(Integer a, Integer b):
-        m_rng(rng()),
-        m_dist(a, b) {
-        static_cast<void>(next());
-    }
-
-    Integer const& get() const override {
-        return m_current_number;
-    }
-    bool next() override {
-        m_current_number = m_dist(m_rng);
-        return true;
-    }
-};
-
-// TODO: Ideally this would be also constrained against the various char types,
-//       but I don't expect users to run into that in practice.
-template <typename T>
-std::enable_if_t<std::is_integral<T>::value && !std::is_same<T, bool>::value,
-GeneratorWrapper<T>>
-random(T a, T b) {
-    return GeneratorWrapper<T>(
-        std::make_unique<RandomIntegerGenerator<T>>(a, b)
-    );
-}
-
-template <typename T>
-std::enable_if_t<std::is_floating_point<T>::value,
-GeneratorWrapper<T>>
-random(T a, T b) {
-    return GeneratorWrapper<T>(
-        std::make_unique<RandomFloatingGenerator<T>>(a, b)
-    );
-}
-
 
 template <typename T>
 class RangeGenerator final : public IGenerator<T> {
@@ -172,4 +106,4 @@ GeneratorWrapper<ResultType> from_range(Container const& cnt) {
 } // namespace Catch
 
 
-#endif // TWOBLUECUBES_CATCH_GENERATORS_SPECIFIC_HPP_INCLUDED
+#endif // TWOBLUECUBES_CATCH_GENERATORS_RANGE_HPP_INCLUDED
diff --git a/src/catch2/catch_interfaces_capture.cpp b/src/catch2/interfaces/catch_interfaces_capture.cpp
similarity index 54%
rename from src/catch2/catch_interfaces_capture.cpp
rename to src/catch2/interfaces/catch_interfaces_capture.cpp
index f73d270c..f49626e0 100644
--- a/src/catch2/catch_interfaces_capture.cpp
+++ b/src/catch2/interfaces/catch_interfaces_capture.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_interfaces_capture.h>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
 
 namespace Catch {
     IResultCapture::~IResultCapture() = default;
diff --git a/src/catch2/catch_interfaces_capture.h b/src/catch2/interfaces/catch_interfaces_capture.hpp
similarity index 97%
rename from src/catch2/catch_interfaces_capture.h
rename to src/catch2/interfaces/catch_interfaces_capture.hpp
index 0a1cfe6d..72fdcbec 100644
--- a/src/catch2/catch_interfaces_capture.h
+++ b/src/catch2/interfaces/catch_interfaces_capture.hpp
@@ -11,8 +11,8 @@
 #include <string>
 #include <chrono>
 
-#include <catch2/catch_stringref.h>
-#include <catch2/catch_result_type.h>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/internal/catch_result_type.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/interfaces/catch_interfaces_config.cpp b/src/catch2/interfaces/catch_interfaces_config.cpp
new file mode 100644
index 00000000..b451278c
--- /dev/null
+++ b/src/catch2/interfaces/catch_interfaces_config.cpp
@@ -0,0 +1,5 @@
+#include <catch2/interfaces/catch_interfaces_config.hpp>
+
+namespace Catch {
+    IConfig::~IConfig() = default;
+}
diff --git a/src/catch2/catch_interfaces_config.h b/src/catch2/interfaces/catch_interfaces_config.hpp
similarity index 97%
rename from src/catch2/catch_interfaces_config.h
rename to src/catch2/interfaces/catch_interfaces_config.hpp
index ddaf2e8e..ca334326 100644
--- a/src/catch2/catch_interfaces_config.h
+++ b/src/catch2/interfaces/catch_interfaces_config.hpp
@@ -8,8 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_INTERFACES_CONFIG_H_INCLUDED
 #define TWOBLUECUBES_CATCH_INTERFACES_CONFIG_H_INCLUDED
 
-#include <catch2/catch_common.h>
-#include <catch2/catch_option.hpp>
+#include <catch2/internal/catch_common.hpp>
 
 #include <chrono>
 #include <iosfwd>
diff --git a/src/catch2/catch_interfaces_enum_values_registry.h b/src/catch2/interfaces/catch_interfaces_enum_values_registry.hpp
similarity index 97%
rename from src/catch2/catch_interfaces_enum_values_registry.h
rename to src/catch2/interfaces/catch_interfaces_enum_values_registry.hpp
index b6134942..2439c630 100644
--- a/src/catch2/catch_interfaces_enum_values_registry.h
+++ b/src/catch2/interfaces/catch_interfaces_enum_values_registry.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_INTERFACESENUMVALUESREGISTRY_H_INCLUDED
 #define TWOBLUECUBES_CATCH_INTERFACESENUMVALUESREGISTRY_H_INCLUDED
 
-#include <catch2/catch_stringref.h>
+#include <catch2/catch_stringref.hpp>
 
 #include <vector>
 
diff --git a/src/catch2/catch_interfaces_exception.cpp b/src/catch2/interfaces/catch_interfaces_exception.cpp
similarity index 72%
rename from src/catch2/catch_interfaces_exception.cpp
rename to src/catch2/interfaces/catch_interfaces_exception.cpp
index b1851d91..6d6db336 100644
--- a/src/catch2/catch_interfaces_exception.cpp
+++ b/src/catch2/interfaces/catch_interfaces_exception.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_interfaces_exception.h>
+#include <catch2/interfaces/catch_interfaces_exception.hpp>
 
 namespace Catch {
     IExceptionTranslator::~IExceptionTranslator() = default;
diff --git a/src/catch2/catch_interfaces_exception.h b/src/catch2/interfaces/catch_interfaces_exception.hpp
similarity index 96%
rename from src/catch2/catch_interfaces_exception.h
rename to src/catch2/interfaces/catch_interfaces_exception.hpp
index 0f9fbd32..3104ef14 100644
--- a/src/catch2/catch_interfaces_exception.h
+++ b/src/catch2/interfaces/catch_interfaces_exception.hpp
@@ -8,8 +8,8 @@
 #ifndef TWOBLUECUBES_CATCH_INTERFACES_EXCEPTION_H_INCLUDED
 #define TWOBLUECUBES_CATCH_INTERFACES_EXCEPTION_H_INCLUDED
 
-#include <catch2/catch_interfaces_registry_hub.h>
-#include <catch2/catch_compiler_capabilities.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
 
 #if defined(CATCH_CONFIG_DISABLE)
     #define INTERNAL_CATCH_TRANSLATE_EXCEPTION_NO_REG( translatorName, signature) \
diff --git a/src/catch2/catch_interfaces_generatortracker.h b/src/catch2/interfaces/catch_interfaces_generatortracker.hpp
similarity index 100%
rename from src/catch2/catch_interfaces_generatortracker.h
rename to src/catch2/interfaces/catch_interfaces_generatortracker.hpp
diff --git a/src/catch2/catch_interfaces_registry_hub.cpp b/src/catch2/interfaces/catch_interfaces_registry_hub.cpp
similarity index 66%
rename from src/catch2/catch_interfaces_registry_hub.cpp
rename to src/catch2/interfaces/catch_interfaces_registry_hub.cpp
index 7ab51d03..1dfd0f6f 100644
--- a/src/catch2/catch_interfaces_registry_hub.cpp
+++ b/src/catch2/interfaces/catch_interfaces_registry_hub.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 namespace Catch {
     IRegistryHub::~IRegistryHub() = default;
diff --git a/src/catch2/catch_interfaces_registry_hub.h b/src/catch2/interfaces/catch_interfaces_registry_hub.hpp
similarity index 98%
rename from src/catch2/catch_interfaces_registry_hub.h
rename to src/catch2/interfaces/catch_interfaces_registry_hub.hpp
index fc63a0d0..e292763d 100644
--- a/src/catch2/catch_interfaces_registry_hub.h
+++ b/src/catch2/interfaces/catch_interfaces_registry_hub.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_INTERFACES_REGISTRY_HUB_H_INCLUDED
 #define TWOBLUECUBES_CATCH_INTERFACES_REGISTRY_HUB_H_INCLUDED
 
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_common.hpp>
 
 #include <string>
 #include <memory>
diff --git a/src/catch2/catch_interfaces_reporter.cpp b/src/catch2/interfaces/catch_interfaces_reporter.cpp
similarity index 96%
rename from src/catch2/catch_interfaces_reporter.cpp
rename to src/catch2/interfaces/catch_interfaces_reporter.cpp
index 0072463e..7e538d38 100644
--- a/src/catch2/catch_interfaces_reporter.cpp
+++ b/src/catch2/interfaces/catch_interfaces_reporter.cpp
@@ -5,10 +5,11 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_interfaces_reporter.h>
-#include <catch2/catch_console_colour.h>
-#include <catch2/catch_list.h>
-#include <catch2/catch_text.h>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_list.hpp>
+#include <catch2/internal/catch_text.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 #include <algorithm>
 #include <iomanip>
diff --git a/src/catch2/catch_interfaces_reporter.h b/src/catch2/interfaces/catch_interfaces_reporter.hpp
similarity index 96%
rename from src/catch2/catch_interfaces_reporter.h
rename to src/catch2/interfaces/catch_interfaces_reporter.hpp
index a4cd9d8b..9edb9951 100644
--- a/src/catch2/catch_interfaces_reporter.h
+++ b/src/catch2/interfaces/catch_interfaces_reporter.hpp
@@ -8,15 +8,15 @@
 #ifndef TWOBLUECUBES_CATCH_INTERFACES_REPORTER_H_INCLUDED
 #define TWOBLUECUBES_CATCH_INTERFACES_REPORTER_H_INCLUDED
 
-#include <catch2/catch_section_info.h>
-#include <catch2/catch_common.h>
+#include <catch2/catch_section_info.hpp>
+#include <catch2/internal/catch_common.hpp>
 #include <catch2/catch_config.hpp>
-#include <catch2/catch_totals.h>
-#include <catch2/catch_test_case_info.h>
-#include <catch2/catch_assertionresult.h>
-#include <catch2/catch_message.h>
-#include <catch2/catch_option.hpp>
-#include <catch2/catch_stringref.h>
+#include <catch2/catch_totals.hpp>
+#include <catch2/catch_test_case_info.hpp>
+#include <catch2/catch_assertion_result.hpp>
+#include <catch2/catch_message.hpp>
+#include <catch2/internal/catch_option.hpp>
+#include <catch2/catch_stringref.hpp>
 
 #include <catch2/benchmark/catch_estimate.hpp>
 #include <catch2/benchmark/catch_outlier_classification.hpp>
diff --git a/src/catch2/interfaces/catch_interfaces_runner.cpp b/src/catch2/interfaces/catch_interfaces_runner.cpp
new file mode 100644
index 00000000..a624b639
--- /dev/null
+++ b/src/catch2/interfaces/catch_interfaces_runner.cpp
@@ -0,0 +1,5 @@
+#include <catch2/interfaces/catch_interfaces_runner.hpp>
+
+namespace Catch {
+    IRunner::~IRunner() = default;
+}
diff --git a/src/catch2/catch_interfaces_runner.h b/src/catch2/interfaces/catch_interfaces_runner.hpp
similarity index 100%
rename from src/catch2/catch_interfaces_runner.h
rename to src/catch2/interfaces/catch_interfaces_runner.hpp
diff --git a/src/catch2/catch_interfaces_tag_alias_registry.h b/src/catch2/interfaces/catch_interfaces_tag_alias_registry.hpp
similarity index 100%
rename from src/catch2/catch_interfaces_tag_alias_registry.h
rename to src/catch2/interfaces/catch_interfaces_tag_alias_registry.hpp
diff --git a/src/catch2/catch_interfaces_testcase.cpp b/src/catch2/interfaces/catch_interfaces_testcase.cpp
similarity index 67%
rename from src/catch2/catch_interfaces_testcase.cpp
rename to src/catch2/interfaces/catch_interfaces_testcase.cpp
index 2635b85a..b43d05c9 100644
--- a/src/catch2/catch_interfaces_testcase.cpp
+++ b/src/catch2/interfaces/catch_interfaces_testcase.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_interfaces_testcase.h>
+#include <catch2/interfaces/catch_interfaces_testcase.hpp>
 
 namespace Catch {
     ITestInvoker::~ITestInvoker() = default;
diff --git a/src/catch2/catch_interfaces_testcase.h b/src/catch2/interfaces/catch_interfaces_testcase.hpp
similarity index 100%
rename from src/catch2/catch_interfaces_testcase.h
rename to src/catch2/interfaces/catch_interfaces_testcase.hpp
diff --git a/src/catch2/catch_assertionhandler.cpp b/src/catch2/internal/catch_assertionhandler.cpp
similarity index 89%
rename from src/catch2/catch_assertionhandler.cpp
rename to src/catch2/internal/catch_assertionhandler.cpp
index 9d321a52..0fe95f50 100644
--- a/src/catch2/catch_assertionhandler.cpp
+++ b/src/catch2/internal/catch_assertionhandler.cpp
@@ -6,16 +6,16 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_assertionhandler.h>
-#include <catch2/catch_assertionresult.h>
-#include <catch2/catch_interfaces_runner.h>
-#include <catch2/catch_interfaces_config.h>
-#include <catch2/catch_context.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_debugger.h>
-#include <catch2/catch_interfaces_registry_hub.h>
-#include <catch2/internal/catch_capture_matchers.h>
-#include <catch2/catch_run_context.h>
+#include <catch2/internal/catch_assertionhandler.hpp>
+#include <catch2/catch_assertion_result.hpp>
+#include <catch2/interfaces/catch_interfaces_runner.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_debugger.hpp>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
+#include <catch2/internal/catch_capture_matchers.hpp>
+#include <catch2/internal/catch_run_context.hpp>
 #include <catch2/matchers/catch_matchers_string.hpp>
 
 namespace Catch {
diff --git a/src/catch2/catch_assertionhandler.h b/src/catch2/internal/catch_assertionhandler.hpp
similarity index 94%
rename from src/catch2/catch_assertionhandler.h
rename to src/catch2/internal/catch_assertionhandler.hpp
index 6afbf93a..b3bf031d 100644
--- a/src/catch2/catch_assertionhandler.h
+++ b/src/catch2/internal/catch_assertionhandler.hpp
@@ -8,9 +8,9 @@
 #ifndef TWOBLUECUBES_CATCH_ASSERTIONHANDLER_H_INCLUDED
 #define TWOBLUECUBES_CATCH_ASSERTIONHANDLER_H_INCLUDED
 
-#include <catch2/catch_assertioninfo.h>
-#include <catch2/catch_decomposer.h>
-#include <catch2/catch_interfaces_capture.h>
+#include <catch2/catch_assertion_info.hpp>
+#include <catch2/internal/catch_decomposer.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_capture.hpp b/src/catch2/internal/catch_capture.hpp
similarity index 97%
rename from src/catch2/catch_capture.hpp
rename to src/catch2/internal/catch_capture.hpp
index 2b5cfa90..369076a7 100644
--- a/src/catch2/catch_capture.hpp
+++ b/src/catch2/internal/catch_capture.hpp
@@ -8,10 +8,10 @@
 #ifndef TWOBLUECUBES_CATCH_CAPTURE_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_CAPTURE_HPP_INCLUDED
 
-#include <catch2/catch_assertionhandler.h>
-#include <catch2/catch_interfaces_capture.h>
-#include <catch2/catch_message.h>
-#include <catch2/catch_stringref.h>
+#include <catch2/internal/catch_assertionhandler.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
+#include <catch2/catch_message.hpp>
+#include <catch2/catch_stringref.hpp>
 
 // We need this suppression to leak, because it took until GCC 9
 // for the front end to handle local suppression via _Pragma properly
diff --git a/src/catch2/internal/catch_capture_matchers.cpp b/src/catch2/internal/catch_capture_matchers.cpp
index 750a0e91..90f0c084 100644
--- a/src/catch2/internal/catch_capture_matchers.cpp
+++ b/src/catch2/internal/catch_capture_matchers.cpp
@@ -2,9 +2,9 @@
  *  Distributed under the Boost Software License, Version 1.0. (See accompanying
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
-#include <catch2/internal/catch_capture_matchers.h>
+#include <catch2/internal/catch_capture_matchers.hpp>
 #include <catch2/matchers/catch_matchers.hpp>
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/internal/catch_capture_matchers.h b/src/catch2/internal/catch_capture_matchers.hpp
similarity index 97%
rename from src/catch2/internal/catch_capture_matchers.h
rename to src/catch2/internal/catch_capture_matchers.hpp
index 1b622413..b66a25dd 100644
--- a/src/catch2/internal/catch_capture_matchers.h
+++ b/src/catch2/internal/catch_capture_matchers.hpp
@@ -5,8 +5,8 @@
 #ifndef TWOBLUECUBES_CATCH_CAPTURE_MATCHERS_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_CAPTURE_MATCHERS_HPP_INCLUDED
 
-#include <catch2/catch_capture.hpp>
-#include <catch2/catch_stringref.h>
+#include <catch2/internal/catch_capture.hpp>
+#include <catch2/catch_stringref.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_clara.h b/src/catch2/internal/catch_clara.hpp
similarity index 100%
rename from src/catch2/catch_clara.h
rename to src/catch2/internal/catch_clara.hpp
diff --git a/src/catch2/catch_commandline.cpp b/src/catch2/internal/catch_commandline.cpp
similarity index 97%
rename from src/catch2/catch_commandline.cpp
rename to src/catch2/internal/catch_commandline.cpp
index 6ed626a1..9890ca64 100644
--- a/src/catch2/catch_commandline.cpp
+++ b/src/catch2/internal/catch_commandline.cpp
@@ -6,12 +6,12 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_commandline.h>
+#include <catch2/internal/catch_commandline.hpp>
 
-#include <catch2/catch_string_manip.h>
+#include <catch2/internal/catch_string_manip.hpp>
 
-#include <catch2/catch_interfaces_registry_hub.h>
-#include <catch2/catch_interfaces_reporter.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
 
 #include <fstream>
 #include <ctime>
diff --git a/src/catch2/catch_commandline.h b/src/catch2/internal/catch_commandline.hpp
similarity index 92%
rename from src/catch2/catch_commandline.h
rename to src/catch2/internal/catch_commandline.hpp
index 3761f2ff..0824397d 100644
--- a/src/catch2/catch_commandline.h
+++ b/src/catch2/internal/catch_commandline.hpp
@@ -9,7 +9,7 @@
 #define TWOBLUECUBES_CATCH_COMMANDLINE_HPP_INCLUDED
 
 #include <catch2/catch_config.hpp>
-#include <catch2/catch_clara.h>
+#include <catch2/internal/catch_clara.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_common.cpp b/src/catch2/internal/catch_common.cpp
similarity index 89%
rename from src/catch2/catch_common.cpp
rename to src/catch2/internal/catch_common.cpp
index 12819963..5398540f 100644
--- a/src/catch2/catch_common.cpp
+++ b/src/catch2/internal/catch_common.cpp
@@ -6,9 +6,9 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_common.h>
-#include <catch2/catch_context.h>
-#include <catch2/catch_interfaces_config.h>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
 
 #include <cstring>
 #include <ostream>
diff --git a/src/catch2/catch_common.h b/src/catch2/internal/catch_common.hpp
similarity index 98%
rename from src/catch2/catch_common.h
rename to src/catch2/internal/catch_common.hpp
index 392576d6..75f82d03 100644
--- a/src/catch2/catch_common.h
+++ b/src/catch2/internal/catch_common.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_COMMON_H_INCLUDED
 #define TWOBLUECUBES_CATCH_COMMON_H_INCLUDED
 
-#include <catch2/catch_compiler_capabilities.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
 
 #define INTERNAL_CATCH_UNIQUE_NAME_LINE2( name, line ) name##line
 #define INTERNAL_CATCH_UNIQUE_NAME_LINE( name, line ) INTERNAL_CATCH_UNIQUE_NAME_LINE2( name, line )
diff --git a/src/catch2/catch_compiler_capabilities.h b/src/catch2/internal/catch_compiler_capabilities.hpp
similarity index 99%
rename from src/catch2/catch_compiler_capabilities.h
rename to src/catch2/internal/catch_compiler_capabilities.hpp
index 5cb739ea..63641030 100644
--- a/src/catch2/catch_compiler_capabilities.h
+++ b/src/catch2/internal/catch_compiler_capabilities.hpp
@@ -25,7 +25,7 @@
 // Many features, at point of detection, define an _INTERNAL_ macro, so they
 // can be combined, en-mass, with the _NO_ forms later.
 
-#include <catch2/catch_platform.h>
+#include <catch2/internal/catch_platform.hpp>
 
 #ifdef __cplusplus
 
diff --git a/src/catch2/catch_console_colour.cpp b/src/catch2/internal/catch_console_colour.cpp
similarity index 94%
rename from src/catch2/catch_console_colour.cpp
rename to src/catch2/internal/catch_console_colour.cpp
index 07b150cb..ee75e2ec 100644
--- a/src/catch2/catch_console_colour.cpp
+++ b/src/catch2/internal/catch_console_colour.cpp
@@ -13,15 +13,15 @@
 #endif
 
 
-#include <catch2/catch_console_colour.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_errno_guard.h>
-#include <catch2/catch_interfaces_config.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_context.h>
-#include <catch2/catch_platform.h>
-#include <catch2/catch_debugger.h>
-#include <catch2/catch_windows_h_proxy.h>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_errno_guard.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_platform.hpp>
+#include <catch2/internal/catch_debugger.hpp>
+#include <catch2/internal/catch_windows_h_proxy.hpp>
 
 #include <sstream>
 
diff --git a/src/catch2/catch_console_colour.h b/src/catch2/internal/catch_console_colour.hpp
similarity index 97%
rename from src/catch2/catch_console_colour.h
rename to src/catch2/internal/catch_console_colour.hpp
index b26459e1..d0bb6daf 100644
--- a/src/catch2/catch_console_colour.h
+++ b/src/catch2/internal/catch_console_colour.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_CONSOLE_COLOUR_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_CONSOLE_COLOUR_HPP_INCLUDED
 
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_common.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/internal/catch_container_nonmembers.hpp b/src/catch2/internal/catch_container_nonmembers.hpp
index 781b3dc4..6057452e 100644
--- a/src/catch2/internal/catch_container_nonmembers.hpp
+++ b/src/catch2/internal/catch_container_nonmembers.hpp
@@ -4,7 +4,7 @@
 #ifndef TWOBLUECUBES_CATCH_CONTAINER_NONMEMBERS_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_CONTAINER_NONMEMBERS_HPP_INCLUDED
 
-#include <catch2/catch_compiler_capabilities.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
 
 
 // We want a simple polyfill over `std::empty`, `std::size` and so on
diff --git a/src/catch2/catch_context.cpp b/src/catch2/internal/catch_context.cpp
similarity index 92%
rename from src/catch2/catch_context.cpp
rename to src/catch2/internal/catch_context.cpp
index 6dbc7a3d..d39d5e43 100644
--- a/src/catch2/catch_context.cpp
+++ b/src/catch2/internal/catch_context.cpp
@@ -5,9 +5,9 @@
  *  Distributed under the Boost Software License, Version 1.0. (See accompanying
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
-#include <catch2/catch_context.h>
-#include <catch2/catch_common.h>
-#include <catch2/catch_random_number_generator.h>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/internal/catch_random_number_generator.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_context.h b/src/catch2/internal/catch_context.hpp
similarity index 100%
rename from src/catch2/catch_context.h
rename to src/catch2/internal/catch_context.hpp
diff --git a/src/catch2/catch_debug_console.cpp b/src/catch2/internal/catch_debug_console.cpp
similarity index 77%
rename from src/catch2/catch_debug_console.cpp
rename to src/catch2/internal/catch_debug_console.cpp
index 8dac5b0c..ced693f3 100644
--- a/src/catch2/catch_debug_console.cpp
+++ b/src/catch2/internal/catch_debug_console.cpp
@@ -6,11 +6,11 @@
  *
  */
 
-#include <catch2/catch_debug_console.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_platform.h>
-#include <catch2/catch_windows_h_proxy.h>
+#include <catch2/internal/catch_debug_console.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/internal/catch_platform.hpp>
+#include <catch2/internal/catch_windows_h_proxy.hpp>
 
 #if defined(CATCH_CONFIG_ANDROID_LOGWRITE)
 #include <android/log.h>
diff --git a/src/catch2/catch_debug_console.h b/src/catch2/internal/catch_debug_console.hpp
similarity index 100%
rename from src/catch2/catch_debug_console.h
rename to src/catch2/internal/catch_debug_console.hpp
diff --git a/src/catch2/catch_debugger.cpp b/src/catch2/internal/catch_debugger.cpp
similarity index 95%
rename from src/catch2/catch_debugger.cpp
rename to src/catch2/internal/catch_debugger.cpp
index 068025af..15ab3449 100644
--- a/src/catch2/catch_debugger.cpp
+++ b/src/catch2/internal/catch_debugger.cpp
@@ -7,10 +7,10 @@
  *
  */
 
-#include <catch2/catch_debugger.h>
-#include <catch2/catch_errno_guard.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_platform.h>
+#include <catch2/internal/catch_debugger.hpp>
+#include <catch2/internal/catch_errno_guard.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/internal/catch_platform.hpp>
 
 #if defined(CATCH_PLATFORM_MAC) || defined(CATCH_PLATFORM_IPHONE)
 
diff --git a/src/catch2/catch_debugger.h b/src/catch2/internal/catch_debugger.hpp
similarity index 97%
rename from src/catch2/catch_debugger.h
rename to src/catch2/internal/catch_debugger.hpp
index fa9e5afe..16c68c52 100644
--- a/src/catch2/catch_debugger.h
+++ b/src/catch2/internal/catch_debugger.hpp
@@ -9,7 +9,7 @@
 #ifndef TWOBLUECUBES_CATCH_DEBUGGER_H_INCLUDED
 #define TWOBLUECUBES_CATCH_DEBUGGER_H_INCLUDED
 
-#include <catch2/catch_platform.h>
+#include <catch2/internal/catch_platform.hpp>
 
 namespace Catch {
     bool isDebuggerActive();
diff --git a/src/catch2/catch_decomposer.cpp b/src/catch2/internal/catch_decomposer.cpp
similarity index 94%
rename from src/catch2/catch_decomposer.cpp
rename to src/catch2/internal/catch_decomposer.cpp
index c2c48153..d227c534 100644
--- a/src/catch2/catch_decomposer.cpp
+++ b/src/catch2/internal/catch_decomposer.cpp
@@ -6,7 +6,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_decomposer.h>
+#include <catch2/internal/catch_decomposer.hpp>
 #include <catch2/catch_config.hpp>
 
 namespace Catch {
diff --git a/src/catch2/catch_decomposer.h b/src/catch2/internal/catch_decomposer.hpp
similarity index 98%
rename from src/catch2/catch_decomposer.h
rename to src/catch2/internal/catch_decomposer.hpp
index 18d284e6..7d915f15 100644
--- a/src/catch2/catch_decomposer.h
+++ b/src/catch2/internal/catch_decomposer.hpp
@@ -8,9 +8,9 @@
 #ifndef TWOBLUECUBES_CATCH_DECOMPOSER_H_INCLUDED
 #define TWOBLUECUBES_CATCH_DECOMPOSER_H_INCLUDED
 
-#include <catch2/catch_tostring.h>
-#include <catch2/catch_stringref.h>
-#include <catch2/catch_meta.hpp>
+#include <catch2/catch_tostring.hpp>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/internal/catch_meta.hpp>
 
 #include <iosfwd>
 
diff --git a/src/catch2/catch_default_main.hpp b/src/catch2/internal/catch_default_main.hpp
similarity index 88%
rename from src/catch2/catch_default_main.hpp
rename to src/catch2/internal/catch_default_main.hpp
index 4f769695..faefc70b 100644
--- a/src/catch2/catch_default_main.hpp
+++ b/src/catch2/internal/catch_default_main.hpp
@@ -8,10 +8,10 @@
 #ifndef TWOBLUECUBES_CATCH_DEFAULT_MAIN_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_DEFAULT_MAIN_HPP_INCLUDED
 
-#include <catch2/catch_session.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_leak_detector.h>
-#include <catch2/catch_platform.h>
+#include <catch2/catch_session.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_leak_detector.hpp>
+#include <catch2/internal/catch_platform.hpp>
 
 namespace Catch {
     CATCH_INTERNAL_START_WARNINGS_SUPPRESSION
diff --git a/src/catch2/catch_enforce.cpp b/src/catch2/internal/catch_enforce.cpp
similarity index 95%
rename from src/catch2/catch_enforce.cpp
rename to src/catch2/internal/catch_enforce.cpp
index 06aaad14..d52e23ab 100644
--- a/src/catch2/catch_enforce.cpp
+++ b/src/catch2/internal/catch_enforce.cpp
@@ -5,7 +5,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_enforce.h>
+#include <catch2/internal/catch_enforce.hpp>
 
 #include <stdexcept>
 
diff --git a/src/catch2/catch_enforce.h b/src/catch2/internal/catch_enforce.hpp
similarity index 90%
rename from src/catch2/catch_enforce.h
rename to src/catch2/internal/catch_enforce.hpp
index 846d629b..f9246653 100644
--- a/src/catch2/catch_enforce.h
+++ b/src/catch2/internal/catch_enforce.hpp
@@ -7,9 +7,9 @@
 #ifndef TWOBLUECUBES_CATCH_ENFORCE_H_INCLUDED
 #define TWOBLUECUBES_CATCH_ENFORCE_H_INCLUDED
 
-#include <catch2/catch_common.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_stream.h>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_stream.hpp>
 
 #include <exception>
 
diff --git a/src/catch2/catch_enum_values_registry.cpp b/src/catch2/internal/catch_enum_values_registry.cpp
similarity index 94%
rename from src/catch2/catch_enum_values_registry.cpp
rename to src/catch2/internal/catch_enum_values_registry.cpp
index 11d15dc6..0ab07b57 100644
--- a/src/catch2/catch_enum_values_registry.cpp
+++ b/src/catch2/internal/catch_enum_values_registry.cpp
@@ -5,9 +5,9 @@
  *  Distributed under the Boost Software License, Version 1.0. (See accompanying
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
-#include <catch2/catch_enum_values_registry.h>
-#include <catch2/catch_string_manip.h>
-#include <catch2/catch_stream.h>
+#include <catch2/internal/catch_enum_values_registry.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/internal/catch_stream.hpp>
 
 #include <map>
 #include <cassert>
diff --git a/src/catch2/catch_enum_values_registry.h b/src/catch2/internal/catch_enum_values_registry.hpp
similarity index 93%
rename from src/catch2/catch_enum_values_registry.h
rename to src/catch2/internal/catch_enum_values_registry.hpp
index b057bb40..87494b07 100644
--- a/src/catch2/catch_enum_values_registry.h
+++ b/src/catch2/internal/catch_enum_values_registry.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_ENUMVALUESREGISTRY_H_INCLUDED
 #define TWOBLUECUBES_CATCH_ENUMVALUESREGISTRY_H_INCLUDED
 
-#include <catch2/catch_interfaces_enum_values_registry.h>
+#include <catch2/interfaces/catch_interfaces_enum_values_registry.hpp>
 
 #include <vector>
 #include <memory>
diff --git a/src/catch2/catch_errno_guard.cpp b/src/catch2/internal/catch_errno_guard.cpp
similarity index 87%
rename from src/catch2/catch_errno_guard.cpp
rename to src/catch2/internal/catch_errno_guard.cpp
index a7303e9c..3cc3697c 100644
--- a/src/catch2/catch_errno_guard.cpp
+++ b/src/catch2/internal/catch_errno_guard.cpp
@@ -5,7 +5,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_errno_guard.h>
+#include <catch2/internal/catch_errno_guard.hpp>
 
 #include <cerrno>
 
diff --git a/src/catch2/catch_errno_guard.h b/src/catch2/internal/catch_errno_guard.hpp
similarity index 100%
rename from src/catch2/catch_errno_guard.h
rename to src/catch2/internal/catch_errno_guard.hpp
diff --git a/src/catch2/catch_exception_translator_registry.cpp b/src/catch2/internal/catch_exception_translator_registry.cpp
similarity index 92%
rename from src/catch2/catch_exception_translator_registry.cpp
rename to src/catch2/internal/catch_exception_translator_registry.cpp
index 744621e6..8394bfd7 100644
--- a/src/catch2/catch_exception_translator_registry.cpp
+++ b/src/catch2/internal/catch_exception_translator_registry.cpp
@@ -6,10 +6,10 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_exception_translator_registry.h>
-#include <catch2/catch_assertionhandler.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_enforce.h>
+#include <catch2/internal/catch_exception_translator_registry.hpp>
+#include <catch2/internal/catch_assertionhandler.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_enforce.hpp>
 
 #ifdef __OBJC__
 #import "Foundation/Foundation.h"
diff --git a/src/catch2/catch_exception_translator_registry.h b/src/catch2/internal/catch_exception_translator_registry.hpp
similarity index 94%
rename from src/catch2/catch_exception_translator_registry.h
rename to src/catch2/internal/catch_exception_translator_registry.hpp
index 2708baf2..48c385ab 100644
--- a/src/catch2/catch_exception_translator_registry.h
+++ b/src/catch2/internal/catch_exception_translator_registry.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_EXCEPTION_TRANSLATOR_REGISTRY_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_EXCEPTION_TRANSLATOR_REGISTRY_HPP_INCLUDED
 
-#include <catch2/catch_interfaces_exception.h>
+#include <catch2/interfaces/catch_interfaces_exception.hpp>
 #include <vector>
 #include <string>
 #include <memory>
diff --git a/src/catch2/catch_fatal_condition.cpp b/src/catch2/internal/catch_fatal_condition.cpp
similarity index 97%
rename from src/catch2/catch_fatal_condition.cpp
rename to src/catch2/internal/catch_fatal_condition.cpp
index 9fbd26e3..1a858569 100644
--- a/src/catch2/catch_fatal_condition.cpp
+++ b/src/catch2/internal/catch_fatal_condition.cpp
@@ -7,10 +7,10 @@
  *
  */
 
-#include <catch2/catch_fatal_condition.h>
+#include <catch2/internal/catch_fatal_condition.hpp>
 
-#include <catch2/catch_context.h>
-#include <catch2/catch_interfaces_capture.h>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
 
 #if defined(__GNUC__)
 #    pragma GCC diagnostic push
diff --git a/src/catch2/catch_fatal_condition.h b/src/catch2/internal/catch_fatal_condition.hpp
similarity index 89%
rename from src/catch2/catch_fatal_condition.h
rename to src/catch2/internal/catch_fatal_condition.hpp
index cabd7cab..f7c2064e 100644
--- a/src/catch2/catch_fatal_condition.h
+++ b/src/catch2/internal/catch_fatal_condition.hpp
@@ -9,9 +9,9 @@
 #ifndef TWOBLUECUBES_CATCH_FATAL_CONDITION_H_INCLUDED
 #define TWOBLUECUBES_CATCH_FATAL_CONDITION_H_INCLUDED
 
-#include <catch2/catch_platform.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_windows_h_proxy.h>
+#include <catch2/internal/catch_platform.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_windows_h_proxy.hpp>
 
 
 #if defined( CATCH_CONFIG_WINDOWS_SEH )
diff --git a/src/catch2/catch_leak_detector.cpp b/src/catch2/internal/catch_leak_detector.cpp
similarity index 87%
rename from src/catch2/catch_leak_detector.cpp
rename to src/catch2/internal/catch_leak_detector.cpp
index 67e6c49c..0f3ad29d 100644
--- a/src/catch2/catch_leak_detector.cpp
+++ b/src/catch2/internal/catch_leak_detector.cpp
@@ -5,8 +5,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
- #include <catch2/catch_leak_detector.h>
- #include <catch2/catch_interfaces_registry_hub.h>
+ #include <catch2/internal/catch_leak_detector.hpp>
+ #include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 
 #ifdef CATCH_CONFIG_WINDOWS_CRTDBG
diff --git a/src/catch2/catch_leak_detector.h b/src/catch2/internal/catch_leak_detector.hpp
similarity index 100%
rename from src/catch2/catch_leak_detector.h
rename to src/catch2/internal/catch_leak_detector.hpp
diff --git a/src/catch2/catch_list.cpp b/src/catch2/internal/catch_list.cpp
similarity index 86%
rename from src/catch2/catch_list.cpp
rename to src/catch2/internal/catch_list.cpp
index aac06572..11fb8150 100644
--- a/src/catch2/catch_list.cpp
+++ b/src/catch2/internal/catch_list.cpp
@@ -6,20 +6,19 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_list.h>
+#include <catch2/internal/catch_list.hpp>
 
-#include <catch2/catch_interfaces_registry_hub.h>
-#include <catch2/catch_interfaces_reporter.h>
-#include <catch2/catch_interfaces_testcase.h>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
+#include <catch2/interfaces/catch_interfaces_testcase.hpp>
 
-#include <catch2/catch_context.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_text.h>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_stream.hpp>
 
-#include <catch2/catch_console_colour.h>
-#include <catch2/catch_test_spec_parser.h>
-#include <catch2/catch_tostring.h>
-#include <catch2/catch_string_manip.h>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_test_spec_parser.hpp>
+#include <catch2/catch_tostring.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 #include <limits>
 #include <algorithm>
diff --git a/src/catch2/catch_list.h b/src/catch2/internal/catch_list.hpp
similarity index 95%
rename from src/catch2/catch_list.h
rename to src/catch2/internal/catch_list.hpp
index 08bf2dda..14abea77 100644
--- a/src/catch2/catch_list.h
+++ b/src/catch2/internal/catch_list.hpp
@@ -9,6 +9,7 @@
 #define TWOBLUECUBES_CATCH_LIST_H_INCLUDED
 
 #include <catch2/catch_config.hpp>
+#include <catch2/catch_stringref.hpp>
 
 #include <set>
 #include <string>
@@ -30,8 +31,6 @@ namespace Catch {
         std::size_t count = 0;
     };
 
-    struct testClassInfo {};
-
     bool list( IStreamingReporter& reporter, std::shared_ptr<Config> const& config );
 
 } // end namespace Catch
diff --git a/src/catch2/catch_main.cpp b/src/catch2/internal/catch_main.cpp
similarity index 76%
rename from src/catch2/catch_main.cpp
rename to src/catch2/internal/catch_main.cpp
index 23421afe..8eca23c9 100644
--- a/src/catch2/catch_main.cpp
+++ b/src/catch2/internal/catch_main.cpp
@@ -3,4 +3,4 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
diff --git a/src/catch2/catch_meta.hpp b/src/catch2/internal/catch_meta.hpp
similarity index 100%
rename from src/catch2/catch_meta.hpp
rename to src/catch2/internal/catch_meta.hpp
diff --git a/src/catch2/catch_option.hpp b/src/catch2/internal/catch_option.hpp
similarity index 100%
rename from src/catch2/catch_option.hpp
rename to src/catch2/internal/catch_option.hpp
diff --git a/src/catch2/catch_output_redirect.cpp b/src/catch2/internal/catch_output_redirect.cpp
similarity index 97%
rename from src/catch2/catch_output_redirect.cpp
rename to src/catch2/internal/catch_output_redirect.cpp
index 5ff7abd0..10c3e2ab 100644
--- a/src/catch2/catch_output_redirect.cpp
+++ b/src/catch2/internal/catch_output_redirect.cpp
@@ -5,8 +5,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_output_redirect.h>
-#include <catch2/catch_enforce.h>
+#include <catch2/internal/catch_output_redirect.hpp>
+#include <catch2/internal/catch_enforce.hpp>
 
 #include <cstdio>
 #include <cstring>
diff --git a/src/catch2/catch_output_redirect.h b/src/catch2/internal/catch_output_redirect.hpp
similarity index 97%
rename from src/catch2/catch_output_redirect.h
rename to src/catch2/internal/catch_output_redirect.hpp
index a6cd0594..c3689ff7 100644
--- a/src/catch2/catch_output_redirect.h
+++ b/src/catch2/internal/catch_output_redirect.hpp
@@ -7,8 +7,8 @@
 #ifndef TWOBLUECUBES_CATCH_OUTPUT_REDIRECT_H
 #define TWOBLUECUBES_CATCH_OUTPUT_REDIRECT_H
 
-#include <catch2/catch_platform.h>
-#include <catch2/catch_stream.h>
+#include <catch2/internal/catch_platform.hpp>
+#include <catch2/internal/catch_stream.hpp>
 
 #include <cstdio>
 #include <iosfwd>
diff --git a/src/catch2/catch_platform.h b/src/catch2/internal/catch_platform.hpp
similarity index 88%
rename from src/catch2/catch_platform.h
rename to src/catch2/internal/catch_platform.hpp
index e14cd332..6d9b737e 100644
--- a/src/catch2/catch_platform.h
+++ b/src/catch2/internal/catch_platform.hpp
@@ -6,8 +6,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  *
  */
-#ifndef TWOBLUECUBES_CATCH_PLATFORM_H_INCLUDED
-#define TWOBLUECUBES_CATCH_PLATFORM_H_INCLUDED
+#ifndef TWOBLUECUBES_CATCH_PLATFORM_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_PLATFORM_HPP_INCLUDED
 
 #ifdef __APPLE__
 # include <TargetConditionals.h>
diff --git a/src/catch2/catch_polyfills.cpp b/src/catch2/internal/catch_polyfills.cpp
similarity index 92%
rename from src/catch2/catch_polyfills.cpp
rename to src/catch2/internal/catch_polyfills.cpp
index 65399d8d..a4d54ea8 100644
--- a/src/catch2/catch_polyfills.cpp
+++ b/src/catch2/internal/catch_polyfills.cpp
@@ -5,7 +5,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_polyfills.hpp>
+#include <catch2/internal/catch_polyfills.hpp>
 
 #include <cmath>
 
diff --git a/src/catch2/catch_polyfills.hpp b/src/catch2/internal/catch_polyfills.hpp
similarity index 100%
rename from src/catch2/catch_polyfills.hpp
rename to src/catch2/internal/catch_polyfills.hpp
diff --git a/src/catch2/catch_preprocessor.hpp b/src/catch2/internal/catch_preprocessor.hpp
similarity index 100%
rename from src/catch2/catch_preprocessor.hpp
rename to src/catch2/internal/catch_preprocessor.hpp
diff --git a/src/catch2/catch_random_number_generator.cpp b/src/catch2/internal/catch_random_number_generator.cpp
similarity index 89%
rename from src/catch2/catch_random_number_generator.cpp
rename to src/catch2/internal/catch_random_number_generator.cpp
index 472dcab3..85c923b9 100644
--- a/src/catch2/catch_random_number_generator.cpp
+++ b/src/catch2/internal/catch_random_number_generator.cpp
@@ -5,10 +5,10 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_random_number_generator.h>
-#include <catch2/catch_context.h>
-#include <catch2/catch_run_context.h>
-#include <catch2/catch_interfaces_config.h>
+#include <catch2/internal/catch_random_number_generator.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_run_context.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_random_number_generator.h b/src/catch2/internal/catch_random_number_generator.hpp
similarity index 100%
rename from src/catch2/catch_random_number_generator.h
rename to src/catch2/internal/catch_random_number_generator.hpp
diff --git a/src/catch2/catch_reporter_registry.cpp b/src/catch2/internal/catch_reporter_registry.cpp
similarity index 97%
rename from src/catch2/catch_reporter_registry.cpp
rename to src/catch2/internal/catch_reporter_registry.cpp
index c7fb52ea..9c37b7b2 100644
--- a/src/catch2/catch_reporter_registry.cpp
+++ b/src/catch2/internal/catch_reporter_registry.cpp
@@ -4,7 +4,7 @@
  *  Distributed under the Boost Software License, Version 1.0. (See accompanying
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
-#include <catch2/catch_reporter_registry.h>
+#include <catch2/internal/catch_reporter_registry.hpp>
 
 #include <catch2/catch_reporter_registrars.hpp>
 #include <catch2/reporters/catch_reporter_automake.hpp>
diff --git a/src/catch2/catch_reporter_registry.h b/src/catch2/internal/catch_reporter_registry.hpp
similarity index 94%
rename from src/catch2/catch_reporter_registry.h
rename to src/catch2/internal/catch_reporter_registry.hpp
index e885b0c3..ab073959 100644
--- a/src/catch2/catch_reporter_registry.h
+++ b/src/catch2/internal/catch_reporter_registry.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_REPORTER_REGISTRY_H_INCLUDED
 #define TWOBLUECUBES_CATCH_REPORTER_REGISTRY_H_INCLUDED
 
-#include <catch2/catch_interfaces_reporter.h>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
 
 #include <map>
 
diff --git a/src/catch2/catch_result_type.cpp b/src/catch2/internal/catch_result_type.cpp
similarity index 95%
rename from src/catch2/catch_result_type.cpp
rename to src/catch2/internal/catch_result_type.cpp
index 6c4c9a89..1abead72 100644
--- a/src/catch2/catch_result_type.cpp
+++ b/src/catch2/internal/catch_result_type.cpp
@@ -6,7 +6,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_result_type.h>
+#include <catch2/internal/catch_result_type.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_result_type.h b/src/catch2/internal/catch_result_type.hpp
similarity index 100%
rename from src/catch2/catch_result_type.h
rename to src/catch2/internal/catch_result_type.hpp
diff --git a/src/catch2/catch_run_context.cpp b/src/catch2/internal/catch_run_context.cpp
similarity index 97%
rename from src/catch2/catch_run_context.cpp
rename to src/catch2/internal/catch_run_context.cpp
index 1875468f..d4b6bdac 100644
--- a/src/catch2/catch_run_context.cpp
+++ b/src/catch2/internal/catch_run_context.cpp
@@ -1,10 +1,12 @@
-#include <catch2/catch_run_context.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_context.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_random_number_generator.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_output_redirect.h>
+#include <catch2/internal/catch_run_context.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_fatal_condition.hpp>
+#include <catch2/internal/catch_random_number_generator.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/catch_timer.hpp>
+#include <catch2/internal/catch_output_redirect.hpp>
 
 #include <cassert>
 #include <algorithm>
diff --git a/src/catch2/catch_run_context.h b/src/catch2/internal/catch_run_context.hpp
similarity index 90%
rename from src/catch2/catch_run_context.h
rename to src/catch2/internal/catch_run_context.hpp
index d51260ab..9fd78324 100644
--- a/src/catch2/catch_run_context.h
+++ b/src/catch2/internal/catch_run_context.hpp
@@ -8,20 +8,18 @@
 #ifndef TWOBLUECUBES_CATCH_RUNNER_IMPL_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_RUNNER_IMPL_HPP_INCLUDED
 
-#include <catch2/catch_interfaces_generatortracker.h>
-#include <catch2/catch_interfaces_runner.h>
-#include <catch2/catch_interfaces_reporter.h>
-#include <catch2/catch_interfaces_exception.h>
+#include <catch2/interfaces/catch_interfaces_generatortracker.hpp>
+#include <catch2/interfaces/catch_interfaces_runner.hpp>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
+#include <catch2/interfaces/catch_interfaces_exception.hpp>
 #include <catch2/catch_config.hpp>
-#include <catch2/catch_test_registry.h>
-#include <catch2/catch_test_case_info.h>
-#include <catch2/catch_capture.hpp>
-#include <catch2/catch_totals.h>
-#include <catch2/catch_test_spec.h>
-#include <catch2/catch_test_case_tracker.h>
-#include <catch2/catch_timer.h>
-#include <catch2/catch_assertionhandler.h>
-#include <catch2/catch_fatal_condition.h>
+#include <catch2/internal/catch_test_registry.hpp>
+#include <catch2/catch_test_case_info.hpp>
+#include <catch2/internal/catch_capture.hpp>
+#include <catch2/catch_totals.hpp>
+#include <catch2/catch_test_spec.hpp>
+#include <catch2/internal/catch_test_case_tracker.hpp>
+#include <catch2/internal/catch_assertionhandler.hpp>
 
 #include <string>
 
diff --git a/src/catch2/catch_section.cpp b/src/catch2/internal/catch_section.cpp
similarity index 87%
rename from src/catch2/catch_section.cpp
rename to src/catch2/internal/catch_section.cpp
index 9872cacf..9a542882 100644
--- a/src/catch2/catch_section.cpp
+++ b/src/catch2/internal/catch_section.cpp
@@ -6,9 +6,9 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_section.h>
-#include <catch2/catch_capture.hpp>
-#include <catch2/catch_uncaught_exceptions.h>
+#include <catch2/internal/catch_section.hpp>
+#include <catch2/internal/catch_capture.hpp>
+#include <catch2/internal/catch_uncaught_exceptions.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_section.h b/src/catch2/internal/catch_section.hpp
similarity index 90%
rename from src/catch2/catch_section.h
rename to src/catch2/internal/catch_section.hpp
index 75a5b3ea..f0296f51 100644
--- a/src/catch2/catch_section.h
+++ b/src/catch2/internal/catch_section.hpp
@@ -8,10 +8,10 @@
 #ifndef TWOBLUECUBES_CATCH_SECTION_H_INCLUDED
 #define TWOBLUECUBES_CATCH_SECTION_H_INCLUDED
 
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_section_info.h>
-#include <catch2/catch_totals.h>
-#include <catch2/catch_timer.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/catch_section_info.hpp>
+#include <catch2/catch_timer.hpp>
+#include <catch2/catch_totals.hpp>
 
 #include <string>
 
diff --git a/src/catch2/catch_singletons.cpp b/src/catch2/internal/catch_singletons.cpp
similarity index 95%
rename from src/catch2/catch_singletons.cpp
rename to src/catch2/internal/catch_singletons.cpp
index 67354517..c767883a 100644
--- a/src/catch2/catch_singletons.cpp
+++ b/src/catch2/internal/catch_singletons.cpp
@@ -5,7 +5,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_singletons.hpp>
+#include <catch2/internal/catch_singletons.hpp>
 
 #include <vector>
 
diff --git a/src/catch2/catch_singletons.hpp b/src/catch2/internal/catch_singletons.hpp
similarity index 100%
rename from src/catch2/catch_singletons.hpp
rename to src/catch2/internal/catch_singletons.hpp
diff --git a/src/catch2/catch_startup_exception_registry.cpp b/src/catch2/internal/catch_startup_exception_registry.cpp
similarity index 86%
rename from src/catch2/catch_startup_exception_registry.cpp
rename to src/catch2/internal/catch_startup_exception_registry.cpp
index 38eb6666..8fd7034b 100644
--- a/src/catch2/catch_startup_exception_registry.cpp
+++ b/src/catch2/internal/catch_startup_exception_registry.cpp
@@ -6,8 +6,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_startup_exception_registry.h>
-#include <catch2/catch_compiler_capabilities.h>
+#include <catch2/internal/catch_startup_exception_registry.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
 
 namespace Catch {
 void StartupExceptionRegistry::add( std::exception_ptr const& exception ) noexcept {
diff --git a/src/catch2/catch_startup_exception_registry.h b/src/catch2/internal/catch_startup_exception_registry.hpp
similarity index 100%
rename from src/catch2/catch_startup_exception_registry.h
rename to src/catch2/internal/catch_startup_exception_registry.hpp
diff --git a/src/catch2/catch_stream.cpp b/src/catch2/internal/catch_stream.cpp
similarity index 95%
rename from src/catch2/catch_stream.cpp
rename to src/catch2/internal/catch_stream.cpp
index 23a43001..5a29441b 100644
--- a/src/catch2/catch_stream.cpp
+++ b/src/catch2/internal/catch_stream.cpp
@@ -7,12 +7,12 @@
  *
  */
 
-#include <catch2/catch_common.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_stream.h>
-#include <catch2/catch_debug_console.h>
-#include <catch2/catch_stringref.h>
-#include <catch2/catch_singletons.hpp>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/internal/catch_debug_console.hpp>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/internal/catch_singletons.hpp>
 
 #include <cstdio>
 #include <iostream>
diff --git a/src/catch2/catch_stream.h b/src/catch2/internal/catch_stream.hpp
similarity index 97%
rename from src/catch2/catch_stream.h
rename to src/catch2/internal/catch_stream.hpp
index 261a80e1..557797ae 100644
--- a/src/catch2/catch_stream.h
+++ b/src/catch2/internal/catch_stream.hpp
@@ -9,7 +9,7 @@
 #ifndef TWOBLUECUBES_CATCH_STREAM_H_INCLUDED
 #define TWOBLUECUBES_CATCH_STREAM_H_INCLUDED
 
-#include "catch_common.h"
+#include <catch2/internal/catch_common.hpp>
 
 #include <iosfwd>
 #include <cstddef>
diff --git a/src/catch2/catch_string_manip.cpp b/src/catch2/internal/catch_string_manip.cpp
similarity index 97%
rename from src/catch2/catch_string_manip.cpp
rename to src/catch2/internal/catch_string_manip.cpp
index 93190f5a..4e9322da 100644
--- a/src/catch2/catch_string_manip.cpp
+++ b/src/catch2/internal/catch_string_manip.cpp
@@ -5,8 +5,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_string_manip.h>
-#include <catch2/catch_stringref.h>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/catch_stringref.hpp>
 
 #include <algorithm>
 #include <ostream>
diff --git a/src/catch2/catch_string_manip.h b/src/catch2/internal/catch_string_manip.hpp
similarity index 97%
rename from src/catch2/catch_string_manip.h
rename to src/catch2/internal/catch_string_manip.hpp
index 61595896..f0b36a69 100644
--- a/src/catch2/catch_string_manip.h
+++ b/src/catch2/internal/catch_string_manip.hpp
@@ -7,7 +7,7 @@
 #ifndef TWOBLUECUBES_CATCH_STRING_MANIP_H_INCLUDED
 #define TWOBLUECUBES_CATCH_STRING_MANIP_H_INCLUDED
 
-#include <catch2/catch_stringref.h>
+#include <catch2/catch_stringref.hpp>
 
 #include <string>
 #include <iosfwd>
diff --git a/src/catch2/catch_stringref.cpp b/src/catch2/internal/catch_stringref.cpp
similarity index 94%
rename from src/catch2/catch_stringref.cpp
rename to src/catch2/internal/catch_stringref.cpp
index 1ae57047..53e224eb 100644
--- a/src/catch2/catch_stringref.cpp
+++ b/src/catch2/internal/catch_stringref.cpp
@@ -5,8 +5,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_stringref.h>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/catch_stringref.hpp>
 
 #include <algorithm>
 #include <ostream>
diff --git a/src/catch2/catch_tag_alias_registry.cpp b/src/catch2/internal/catch_tag_alias_registry.cpp
similarity index 88%
rename from src/catch2/catch_tag_alias_registry.cpp
rename to src/catch2/internal/catch_tag_alias_registry.cpp
index 7f850353..7a3d397e 100644
--- a/src/catch2/catch_tag_alias_registry.cpp
+++ b/src/catch2/internal/catch_tag_alias_registry.cpp
@@ -6,11 +6,11 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_tag_alias_registry.h>
-#include <catch2/catch_console_colour.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_interfaces_registry_hub.h>
-#include <catch2/catch_string_manip.h>
+#include <catch2/internal/catch_tag_alias_registry.hpp>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 #include <sstream>
 
diff --git a/src/catch2/catch_tag_alias_registry.h b/src/catch2/internal/catch_tag_alias_registry.hpp
similarity index 89%
rename from src/catch2/catch_tag_alias_registry.h
rename to src/catch2/internal/catch_tag_alias_registry.hpp
index 3936b8e6..47cc726b 100644
--- a/src/catch2/catch_tag_alias_registry.h
+++ b/src/catch2/internal/catch_tag_alias_registry.hpp
@@ -8,8 +8,8 @@
 #ifndef TWOBLUECUBES_CATCH_TAG_ALIAS_REGISTRY_H_INCLUDED
 #define TWOBLUECUBES_CATCH_TAG_ALIAS_REGISTRY_H_INCLUDED
 
-#include <catch2/catch_interfaces_tag_alias_registry.h>
-#include <catch2/catch_tag_alias.h>
+#include <catch2/interfaces/catch_interfaces_tag_alias_registry.hpp>
+#include <catch2/catch_tag_alias.hpp>
 
 #include <map>
 
diff --git a/src/catch2/catch_test_case_registry_impl.cpp b/src/catch2/internal/catch_test_case_registry_impl.cpp
similarity index 90%
rename from src/catch2/catch_test_case_registry_impl.cpp
rename to src/catch2/internal/catch_test_case_registry_impl.cpp
index cc7a9e4b..ab324a36 100644
--- a/src/catch2/catch_test_case_registry_impl.cpp
+++ b/src/catch2/internal/catch_test_case_registry_impl.cpp
@@ -5,15 +5,16 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_test_case_registry_impl.h>
+#include <catch2/internal/catch_test_case_registry_impl.hpp>
 
-#include <catch2/catch_context.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_interfaces_registry_hub.h>
-#include <catch2/catch_random_number_generator.h>
-#include <catch2/catch_run_context.h>
-#include <catch2/catch_string_manip.h>
-#include <catch2/catch_test_case_info.h>
+#include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
+#include <catch2/internal/catch_random_number_generator.hpp>
+#include <catch2/internal/catch_run_context.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/catch_test_case_info.hpp>
+#include <catch2/catch_test_spec.hpp>
 
 #include <sstream>
 
diff --git a/src/catch2/catch_test_case_registry_impl.h b/src/catch2/internal/catch_test_case_registry_impl.hpp
similarity index 95%
rename from src/catch2/catch_test_case_registry_impl.h
rename to src/catch2/internal/catch_test_case_registry_impl.hpp
index d2b3e099..5bc27156 100644
--- a/src/catch2/catch_test_case_registry_impl.h
+++ b/src/catch2/internal/catch_test_case_registry_impl.hpp
@@ -8,9 +8,8 @@
 #ifndef TWOBLUECUBES_CATCH_TEST_CASE_REGISTRY_IMPL_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_TEST_CASE_REGISTRY_IMPL_HPP_INCLUDED
 
-#include <catch2/catch_test_registry.h>
-#include <catch2/catch_test_spec.h>
-#include <catch2/catch_interfaces_config.h>
+#include <catch2/internal/catch_test_registry.hpp>
+#include <catch2/interfaces/catch_interfaces_config.hpp>
 
 #include <vector>
 #include <set>
@@ -20,6 +19,7 @@ namespace Catch {
 
     class TestCaseHandle;
     struct IConfig;
+    class TestSpec;
 
     std::vector<TestCaseHandle> sortTests( IConfig const& config, std::vector<TestCaseHandle> const& unsortedTestCases );
 
diff --git a/src/catch2/catch_test_case_tracker.cpp b/src/catch2/internal/catch_test_case_tracker.cpp
similarity index 98%
rename from src/catch2/catch_test_case_tracker.cpp
rename to src/catch2/internal/catch_test_case_tracker.cpp
index 2d179836..4a47a244 100644
--- a/src/catch2/catch_test_case_tracker.cpp
+++ b/src/catch2/internal/catch_test_case_tracker.cpp
@@ -5,10 +5,10 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_test_case_tracker.h>
+#include <catch2/internal/catch_test_case_tracker.hpp>
 
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_string_manip.h>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 #include <algorithm>
 #include <cassert>
diff --git a/src/catch2/catch_test_case_tracker.h b/src/catch2/internal/catch_test_case_tracker.hpp
similarity index 97%
rename from src/catch2/catch_test_case_tracker.h
rename to src/catch2/internal/catch_test_case_tracker.hpp
index 8522116e..3d9cace9 100644
--- a/src/catch2/catch_test_case_tracker.h
+++ b/src/catch2/internal/catch_test_case_tracker.hpp
@@ -8,8 +8,8 @@
 #ifndef TWOBLUECUBES_CATCH_TEST_CASE_TRACKER_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_TEST_CASE_TRACKER_HPP_INCLUDED
 
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_common.hpp>
 
 #include <string>
 #include <vector>
diff --git a/src/catch2/catch_test_registry.cpp b/src/catch2/internal/catch_test_registry.cpp
similarity index 79%
rename from src/catch2/catch_test_registry.cpp
rename to src/catch2/internal/catch_test_registry.cpp
index 5199203b..070fde0d 100644
--- a/src/catch2/catch_test_registry.cpp
+++ b/src/catch2/internal/catch_test_registry.cpp
@@ -5,10 +5,11 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_test_registry.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_test_case_registry_impl.h>
-#include <catch2/catch_interfaces_registry_hub.h>
+#include <catch2/internal/catch_test_registry.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/catch_test_case_info.hpp>
+#include <catch2/internal/catch_test_case_registry_impl.hpp>
+#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_test_registry.h b/src/catch2/internal/catch_test_registry.hpp
similarity index 98%
rename from src/catch2/catch_test_registry.h
rename to src/catch2/internal/catch_test_registry.hpp
index e83753f0..55f5008c 100644
--- a/src/catch2/catch_test_registry.h
+++ b/src/catch2/internal/catch_test_registry.hpp
@@ -8,12 +8,12 @@
 #ifndef TWOBLUECUBES_CATCH_TEST_REGISTRY_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_TEST_REGISTRY_HPP_INCLUDED
 
-#include <catch2/catch_common.h>
-#include <catch2/catch_interfaces_testcase.h>
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_stringref.h>
-#include <catch2/catch_preprocessor.hpp>
-#include <catch2/catch_meta.hpp>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/interfaces/catch_interfaces_testcase.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/catch_stringref.hpp>
+#include <catch2/internal/catch_preprocessor.hpp>
+#include <catch2/internal/catch_meta.hpp>
 
 #include <memory>
 
diff --git a/src/catch2/catch_test_spec_parser.cpp b/src/catch2/internal/catch_test_spec_parser.cpp
similarity index 98%
rename from src/catch2/catch_test_spec_parser.cpp
rename to src/catch2/internal/catch_test_spec_parser.cpp
index d8de256c..923e5bf2 100644
--- a/src/catch2/catch_test_spec_parser.cpp
+++ b/src/catch2/internal/catch_test_spec_parser.cpp
@@ -5,7 +5,9 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_test_spec_parser.h>
+#include <catch2/internal/catch_test_spec_parser.hpp>
+
+#include <catch2/internal/catch_string_manip.hpp>
 
 
 namespace Catch {
diff --git a/src/catch2/catch_test_spec_parser.h b/src/catch2/internal/catch_test_spec_parser.hpp
similarity index 94%
rename from src/catch2/catch_test_spec_parser.h
rename to src/catch2/internal/catch_test_spec_parser.hpp
index cf978fda..087a8737 100644
--- a/src/catch2/catch_test_spec_parser.h
+++ b/src/catch2/internal/catch_test_spec_parser.hpp
@@ -13,9 +13,8 @@
 #pragma clang diagnostic ignored "-Wpadded"
 #endif
 
-#include <catch2/catch_test_spec.h>
-#include <catch2/catch_string_manip.h>
-#include <catch2/catch_interfaces_tag_alias_registry.h>
+#include <catch2/catch_test_spec.hpp>
+#include <catch2/interfaces/catch_interfaces_tag_alias_registry.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_text.h b/src/catch2/internal/catch_text.hpp
similarity index 91%
rename from src/catch2/catch_text.h
rename to src/catch2/internal/catch_text.hpp
index eefbf53d..7a2c2923 100644
--- a/src/catch2/catch_text.h
+++ b/src/catch2/internal/catch_text.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_TEXT_H_INCLUDED
 #define TWOBLUECUBES_CATCH_TEXT_H_INCLUDED
 
-#include <catch2/catch_clara.h>
+#include <catch2/internal/catch_clara.hpp>
 
 namespace Catch {
     using namespace clara::TextFlow;
diff --git a/src/catch2/catch_to_string.hpp b/src/catch2/internal/catch_to_string.hpp
similarity index 86%
rename from src/catch2/catch_to_string.hpp
rename to src/catch2/internal/catch_to_string.hpp
index 662fd6a1..986b3ab8 100644
--- a/src/catch2/catch_to_string.hpp
+++ b/src/catch2/internal/catch_to_string.hpp
@@ -9,8 +9,8 @@
 
 #include <string>
 
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_stream.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_stream.hpp>
 
 namespace Catch {
     template <typename T>
diff --git a/src/catch2/catch_uncaught_exceptions.cpp b/src/catch2/internal/catch_uncaught_exceptions.cpp
similarity index 81%
rename from src/catch2/catch_uncaught_exceptions.cpp
rename to src/catch2/internal/catch_uncaught_exceptions.cpp
index ea75fe36..3c699fb0 100644
--- a/src/catch2/catch_uncaught_exceptions.cpp
+++ b/src/catch2/internal/catch_uncaught_exceptions.cpp
@@ -6,8 +6,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_compiler_capabilities.h>
-#include <catch2/catch_uncaught_exceptions.h>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
+#include <catch2/internal/catch_uncaught_exceptions.hpp>
 #include <exception>
 
 namespace Catch {
diff --git a/src/catch2/catch_uncaught_exceptions.h b/src/catch2/internal/catch_uncaught_exceptions.hpp
similarity index 100%
rename from src/catch2/catch_uncaught_exceptions.h
rename to src/catch2/internal/catch_uncaught_exceptions.hpp
diff --git a/src/catch2/catch_wildcard_pattern.cpp b/src/catch2/internal/catch_wildcard_pattern.cpp
similarity index 91%
rename from src/catch2/catch_wildcard_pattern.cpp
rename to src/catch2/internal/catch_wildcard_pattern.cpp
index 5936e676..9013984f 100644
--- a/src/catch2/catch_wildcard_pattern.cpp
+++ b/src/catch2/internal/catch_wildcard_pattern.cpp
@@ -5,9 +5,9 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_wildcard_pattern.h>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_string_manip.h>
+#include <catch2/internal/catch_wildcard_pattern.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_wildcard_pattern.h b/src/catch2/internal/catch_wildcard_pattern.hpp
similarity index 96%
rename from src/catch2/catch_wildcard_pattern.h
rename to src/catch2/internal/catch_wildcard_pattern.hpp
index 4594f62c..90e05d4b 100644
--- a/src/catch2/catch_wildcard_pattern.h
+++ b/src/catch2/internal/catch_wildcard_pattern.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_WILDCARD_PATTERN_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_WILDCARD_PATTERN_HPP_INCLUDED
 
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_common.hpp>
 
 
 namespace Catch
diff --git a/src/catch2/catch_windows_h_proxy.h b/src/catch2/internal/catch_windows_h_proxy.hpp
similarity index 95%
rename from src/catch2/catch_windows_h_proxy.h
rename to src/catch2/internal/catch_windows_h_proxy.hpp
index b5adee56..079ebef0 100644
--- a/src/catch2/catch_windows_h_proxy.h
+++ b/src/catch2/internal/catch_windows_h_proxy.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_WINDOWS_H_PROXY_H_INCLUDED
 #define TWOBLUECUBES_CATCH_WINDOWS_H_PROXY_H_INCLUDED
 
-#include <catch2/catch_platform.h>
+#include <catch2/internal/catch_platform.hpp>
 
 #if defined(CATCH_PLATFORM_WINDOWS)
 
diff --git a/src/catch2/catch_xmlwriter.cpp b/src/catch2/internal/catch_xmlwriter.cpp
similarity index 99%
rename from src/catch2/catch_xmlwriter.cpp
rename to src/catch2/internal/catch_xmlwriter.cpp
index 4eed4ef7..a641a35c 100644
--- a/src/catch2/catch_xmlwriter.cpp
+++ b/src/catch2/internal/catch_xmlwriter.cpp
@@ -5,9 +5,9 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_xmlwriter.h>
+#include <catch2/internal/catch_xmlwriter.hpp>
 
-#include <catch2/catch_enforce.h>
+#include <catch2/internal/catch_enforce.hpp>
 
 #include <iomanip>
 #include <type_traits>
diff --git a/src/catch2/catch_xmlwriter.h b/src/catch2/internal/catch_xmlwriter.hpp
similarity index 97%
rename from src/catch2/catch_xmlwriter.h
rename to src/catch2/internal/catch_xmlwriter.hpp
index f0a00c57..3102dc6a 100644
--- a/src/catch2/catch_xmlwriter.h
+++ b/src/catch2/internal/catch_xmlwriter.hpp
@@ -8,8 +8,8 @@
 #ifndef TWOBLUECUBES_CATCH_XMLWRITER_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_XMLWRITER_HPP_INCLUDED
 
-#include <catch2/catch_stream.h>
-#include <catch2/catch_compiler_capabilities.h>
+#include <catch2/internal/catch_stream.hpp>
+#include <catch2/internal/catch_compiler_capabilities.hpp>
 
 #include <vector>
 
diff --git a/src/catch2/matchers/catch_matchers.hpp b/src/catch2/matchers/catch_matchers.hpp
index 3e0f2083..eb22168a 100644
--- a/src/catch2/matchers/catch_matchers.hpp
+++ b/src/catch2/matchers/catch_matchers.hpp
@@ -5,8 +5,8 @@
 #ifndef TWOBLUECUBES_CATCH_MATCHERS_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_MATCHERS_HPP_INCLUDED
 
-#include <catch2/catch_common.h>
-#include <catch2/internal/catch_capture_matchers.h>
+#include <catch2/internal/catch_common.hpp>
+#include <catch2/internal/catch_capture_matchers.hpp>
 
 #include <string>
 #include <vector>
diff --git a/src/catch2/matchers/catch_matchers_container_properties.cpp b/src/catch2/matchers/catch_matchers_container_properties.cpp
index d4da71bf..72b7b3df 100644
--- a/src/catch2/matchers/catch_matchers_container_properties.cpp
+++ b/src/catch2/matchers/catch_matchers_container_properties.cpp
@@ -3,7 +3,7 @@
 
 #include <catch2/matchers/catch_matchers_container_properties.hpp>
 
-#include <catch2/catch_stream.h>
+#include <catch2/internal/catch_stream.hpp>
 
 namespace Catch {
 namespace Matchers {
diff --git a/src/catch2/matchers/catch_matchers_floating.cpp b/src/catch2/matchers/catch_matchers_floating.cpp
index ca20110d..f574053f 100644
--- a/src/catch2/matchers/catch_matchers_floating.cpp
+++ b/src/catch2/matchers/catch_matchers_floating.cpp
@@ -6,10 +6,10 @@
  */
 
 #include <catch2/matchers/catch_matchers_floating.hpp>
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_polyfills.hpp>
-#include <catch2/catch_to_string.hpp>
-#include <catch2/catch_tostring.h>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_polyfills.hpp>
+#include <catch2/internal/catch_to_string.hpp>
+#include <catch2/catch_tostring.hpp>
 
 #include <algorithm>
 #include <cmath>
diff --git a/src/catch2/matchers/catch_matchers_predicate.hpp b/src/catch2/matchers/catch_matchers_predicate.hpp
index e589d8be..a0b736cb 100644
--- a/src/catch2/matchers/catch_matchers_predicate.hpp
+++ b/src/catch2/matchers/catch_matchers_predicate.hpp
@@ -7,9 +7,9 @@
 #ifndef TWOBLUECUBES_CATCH_MATCHERS_GENERIC_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_MATCHERS_GENERIC_HPP_INCLUDED
 
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_common.hpp>
 #include <catch2/matchers/catch_matchers.hpp>
-#include <catch2/catch_meta.hpp>
+#include <catch2/internal/catch_meta.hpp>
 
 #include <string>
 #include <utility>
diff --git a/src/catch2/matchers/catch_matchers_string.cpp b/src/catch2/matchers/catch_matchers_string.cpp
index 812888f3..15905283 100644
--- a/src/catch2/matchers/catch_matchers_string.cpp
+++ b/src/catch2/matchers/catch_matchers_string.cpp
@@ -4,8 +4,8 @@
  */
 
 #include <catch2/matchers/catch_matchers_string.hpp>
-#include <catch2/catch_string_manip.h>
-#include <catch2/catch_tostring.h>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/catch_tostring.hpp>
 
 #include <regex>
 
diff --git a/src/catch2/matchers/catch_matchers_templated.hpp b/src/catch2/matchers/catch_matchers_templated.hpp
index 9688dbd4..d1ca7813 100644
--- a/src/catch2/matchers/catch_matchers_templated.hpp
+++ b/src/catch2/matchers/catch_matchers_templated.hpp
@@ -4,9 +4,9 @@
 #ifndef TWOBLUECUBES_CATCH_MATCHERS_TEMPLATED_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_MATCHERS_TEMPLATED_HPP_INCLUDED
 
-#include <catch2/catch_common.h>
+#include <catch2/internal/catch_common.hpp>
 #include <catch2/matchers/catch_matchers.hpp>
-#include <catch2/catch_stringref.h>
+#include <catch2/catch_stringref.hpp>
 
 #include <array>
 #include <algorithm>
diff --git a/src/catch2/matchers/catch_matchers_vector.hpp b/src/catch2/matchers/catch_matchers_vector.hpp
index cd506292..4f3918cb 100644
--- a/src/catch2/matchers/catch_matchers_vector.hpp
+++ b/src/catch2/matchers/catch_matchers_vector.hpp
@@ -9,7 +9,7 @@
 #define TWOBLUECUBES_CATCH_MATCHERS_VECTOR_H_INCLUDED
 
 #include <catch2/matchers/catch_matchers.hpp>
-#include <catch2/catch_approx.h>
+#include <catch2/catch_approx.hpp>
 
 #include <algorithm>
 
diff --git a/src/catch2/reporters/catch_reporter_bases.cpp b/src/catch2/reporters/catch_reporter_bases.cpp
index 60785a69..de302d18 100644
--- a/src/catch2/reporters/catch_reporter_bases.cpp
+++ b/src/catch2/reporters/catch_reporter_bases.cpp
@@ -6,8 +6,8 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_interfaces_reporter.h>
-#include <catch2/catch_errno_guard.h>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
+#include <catch2/internal/catch_errno_guard.hpp>
 #include <catch2/reporters/catch_reporter_bases.hpp>
 
 #include <cstring>
diff --git a/src/catch2/reporters/catch_reporter_bases.hpp b/src/catch2/reporters/catch_reporter_bases.hpp
index 41e8f634..181b34ec 100644
--- a/src/catch2/reporters/catch_reporter_bases.hpp
+++ b/src/catch2/reporters/catch_reporter_bases.hpp
@@ -8,7 +8,7 @@
 #ifndef TWOBLUECUBES_CATCH_REPORTER_BASES_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_REPORTER_BASES_HPP_INCLUDED
 
-#include <catch2/catch_interfaces_reporter.h>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
 
 #include <algorithm>
 #include <cstring>
diff --git a/src/catch2/reporters/catch_reporter_compact.cpp b/src/catch2/reporters/catch_reporter_compact.cpp
index 236af682..8d498e44 100644
--- a/src/catch2/reporters/catch_reporter_compact.cpp
+++ b/src/catch2/reporters/catch_reporter_compact.cpp
@@ -7,7 +7,8 @@
 
 #include <catch2/reporters/catch_reporter_compact.hpp>
 
-#include <catch2/catch_console_colour.h>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 namespace {
 
diff --git a/src/catch2/reporters/catch_reporter_console.cpp b/src/catch2/reporters/catch_reporter_console.cpp
index 9e5c7322..db97296b 100644
--- a/src/catch2/reporters/catch_reporter_console.cpp
+++ b/src/catch2/reporters/catch_reporter_console.cpp
@@ -9,10 +9,11 @@
 #include <catch2/reporters/catch_reporter_console.hpp>
 
 #include <catch2/catch_reporter_registrars.hpp>
-#include <catch2/catch_console_colour.h>
-#include <catch2/catch_version.h>
-#include <catch2/catch_text.h>
-#include <catch2/catch_stringref.h>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/catch_version.hpp>
+#include <catch2/internal/catch_text.hpp>
+#include <catch2/catch_stringref.hpp>
 
 #include <cfloat>
 #include <cstdio>
diff --git a/src/catch2/reporters/catch_reporter_junit.cpp b/src/catch2/reporters/catch_reporter_junit.cpp
index 49a6aa54..e039875e 100644
--- a/src/catch2/reporters/catch_reporter_junit.cpp
+++ b/src/catch2/reporters/catch_reporter_junit.cpp
@@ -10,9 +10,10 @@
 
 #include <catch2/reporters/catch_reporter_junit.hpp>
 
-#include <catch2/catch_tostring.h>
+#include <catch2/catch_tostring.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 #include <catch2/catch_reporter_registrars.hpp>
-#include <catch2/catch_text.h>
+#include <catch2/internal/catch_text.hpp>
 
 #include <cassert>
 #include <sstream>
diff --git a/src/catch2/reporters/catch_reporter_junit.hpp b/src/catch2/reporters/catch_reporter_junit.hpp
index fd7923bf..3a75570a 100644
--- a/src/catch2/reporters/catch_reporter_junit.hpp
+++ b/src/catch2/reporters/catch_reporter_junit.hpp
@@ -9,8 +9,8 @@
 
 
 #include <catch2/reporters/catch_reporter_bases.hpp>
-#include <catch2/catch_xmlwriter.h>
-#include <catch2/catch_timer.h>
+#include <catch2/internal/catch_xmlwriter.hpp>
+#include <catch2/catch_timer.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/reporters/catch_reporter_listening.hpp b/src/catch2/reporters/catch_reporter_listening.hpp
index 8287e4a2..da2a86b2 100644
--- a/src/catch2/reporters/catch_reporter_listening.hpp
+++ b/src/catch2/reporters/catch_reporter_listening.hpp
@@ -7,7 +7,7 @@
 #ifndef TWOBLUECUBES_CATCH_MULTI_REPORTER_H_INCLUDED
 #define TWOBLUECUBES_CATCH_MULTI_REPORTER_H_INCLUDED
 
-#include <catch2/catch_interfaces_reporter.h>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/reporters/catch_reporter_sonarqube.cpp b/src/catch2/reporters/catch_reporter_sonarqube.cpp
index 8d04dd20..b459b999 100644
--- a/src/catch2/reporters/catch_reporter_sonarqube.cpp
+++ b/src/catch2/reporters/catch_reporter_sonarqube.cpp
@@ -5,6 +5,8 @@
 
 #include <catch2/reporters/catch_reporter_sonarqube.hpp>
 
+#include <catch2/internal/catch_string_manip.hpp>
+
 #include <map>
 
 namespace Catch {
diff --git a/src/catch2/reporters/catch_reporter_sonarqube.hpp b/src/catch2/reporters/catch_reporter_sonarqube.hpp
index 66e7c50d..4bad942a 100644
--- a/src/catch2/reporters/catch_reporter_sonarqube.hpp
+++ b/src/catch2/reporters/catch_reporter_sonarqube.hpp
@@ -7,7 +7,7 @@
 
 #include <catch2/reporters/catch_reporter_bases.hpp>
 
-#include <catch2/catch_xmlwriter.h>
+#include <catch2/internal/catch_xmlwriter.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/reporters/catch_reporter_tap.cpp b/src/catch2/reporters/catch_reporter_tap.cpp
index 9eb39957..d0821129 100644
--- a/src/catch2/reporters/catch_reporter_tap.cpp
+++ b/src/catch2/reporters/catch_reporter_tap.cpp
@@ -4,7 +4,8 @@
  */
 
 #include <catch2/reporters/catch_reporter_tap.hpp>
-#include <catch2/catch_console_colour.h>
+#include <catch2/internal/catch_console_colour.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 
 #include <algorithm>
 
diff --git a/src/catch2/reporters/catch_reporter_teamcity.cpp b/src/catch2/reporters/catch_reporter_teamcity.cpp
index 37a0c090..c25707a1 100644
--- a/src/catch2/reporters/catch_reporter_teamcity.cpp
+++ b/src/catch2/reporters/catch_reporter_teamcity.cpp
@@ -5,8 +5,9 @@
 
 #include <catch2/reporters/catch_reporter_teamcity.hpp>
 
-#include <catch2/catch_enforce.h>
-#include <catch2/catch_text.h>
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_text.hpp>
 
 namespace Catch {
 
diff --git a/src/catch2/reporters/catch_reporter_teamcity.hpp b/src/catch2/reporters/catch_reporter_teamcity.hpp
index da54c69a..42f23c9c 100644
--- a/src/catch2/reporters/catch_reporter_teamcity.hpp
+++ b/src/catch2/reporters/catch_reporter_teamcity.hpp
@@ -5,7 +5,7 @@
 #ifndef TWOBLUECUBES_CATCH_REPORTER_TEAMCITY_HPP_INCLUDED
 #define TWOBLUECUBES_CATCH_REPORTER_TEAMCITY_HPP_INCLUDED
 
-#include <catch2/catch_timer.h>
+#include <catch2/catch_timer.hpp>
 #include <catch2/reporters/catch_reporter_bases.hpp>
 
 #include <cstring>
diff --git a/src/catch2/reporters/catch_reporter_xml.cpp b/src/catch2/reporters/catch_reporter_xml.cpp
index f6274937..d1d3279b 100644
--- a/src/catch2/reporters/catch_reporter_xml.cpp
+++ b/src/catch2/reporters/catch_reporter_xml.cpp
@@ -8,9 +8,10 @@
 
 #include <catch2/reporters/catch_reporter_xml.hpp>
 
-#include <catch2/catch_capture.hpp>
+#include <catch2/internal/catch_capture.hpp>
+#include <catch2/internal/catch_string_manip.hpp>
 #include <catch2/catch_reporter_registrars.hpp>
-#include <catch2/catch_list.h>
+#include <catch2/internal/catch_list.hpp>
 
 #if defined(_MSC_VER)
 #pragma warning(push)
diff --git a/src/catch2/reporters/catch_reporter_xml.hpp b/src/catch2/reporters/catch_reporter_xml.hpp
index 3fb26ba7..c240be3e 100644
--- a/src/catch2/reporters/catch_reporter_xml.hpp
+++ b/src/catch2/reporters/catch_reporter_xml.hpp
@@ -9,8 +9,8 @@
 
 #include <catch2/reporters/catch_reporter_bases.hpp>
 
-#include <catch2/catch_xmlwriter.h>
-#include <catch2/catch_timer.h>
+#include <catch2/internal/catch_xmlwriter.hpp>
+#include <catch2/catch_timer.hpp>
 
 
 namespace Catch {
diff --git a/tests/ExtraTests/X01-PrefixedMacros.cpp b/tests/ExtraTests/X01-PrefixedMacros.cpp
index 05eff1ce..3fc23b09 100644
--- a/tests/ExtraTests/X01-PrefixedMacros.cpp
+++ b/tests/ExtraTests/X01-PrefixedMacros.cpp
@@ -1,7 +1,7 @@
 // X11-DisableStringification.cpp
 // Test that Catch's prefixed macros compile and run properly.
 
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 // This won't provide full coverage, but it might be worth checking
 // the other branch as well
 #include <catch2/catch_test_macros.hpp>
diff --git a/tests/ExtraTests/X02-DisabledMacros.cpp b/tests/ExtraTests/X02-DisabledMacros.cpp
index 1c7385c7..10d5c697 100644
--- a/tests/ExtraTests/X02-DisabledMacros.cpp
+++ b/tests/ExtraTests/X02-DisabledMacros.cpp
@@ -2,7 +2,7 @@
 // Test that CATCH_CONFIG_DISABLE turns off TEST_CASE autoregistration
 // and expressions in assertion macros are not run.
 
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 #include <catch2/catch_test_macros.hpp>
 
 #include <iostream>
diff --git a/tests/ExtraTests/X03-DisabledExceptions-DefaultHandler.cpp b/tests/ExtraTests/X03-DisabledExceptions-DefaultHandler.cpp
index fb72826e..5deb30f9 100644
--- a/tests/ExtraTests/X03-DisabledExceptions-DefaultHandler.cpp
+++ b/tests/ExtraTests/X03-DisabledExceptions-DefaultHandler.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 #include <catch2/catch_test_macros.hpp>
 
 TEST_CASE("Tests that run") {
diff --git a/tests/ExtraTests/X04-DisabledExceptions-CustomHandler.cpp b/tests/ExtraTests/X04-DisabledExceptions-CustomHandler.cpp
index 82d6edfa..0870e9ca 100644
--- a/tests/ExtraTests/X04-DisabledExceptions-CustomHandler.cpp
+++ b/tests/ExtraTests/X04-DisabledExceptions-CustomHandler.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 #include <catch2/catch_test_macros.hpp>
 
 namespace Catch {
diff --git a/tests/ExtraTests/X10-FallbackStringifier.cpp b/tests/ExtraTests/X10-FallbackStringifier.cpp
index a52f371f..900d23e7 100644
--- a/tests/ExtraTests/X10-FallbackStringifier.cpp
+++ b/tests/ExtraTests/X10-FallbackStringifier.cpp
@@ -9,7 +9,7 @@ std::string fallbackStringifier(T const&) {
     return "{ !!! }";
 }
 
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 #include <catch2/catch_test_macros.hpp>
 
 struct foo {
diff --git a/tests/ExtraTests/X11-DisableStringification.cpp b/tests/ExtraTests/X11-DisableStringification.cpp
index 0d84771d..5cd32f12 100644
--- a/tests/ExtraTests/X11-DisableStringification.cpp
+++ b/tests/ExtraTests/X11-DisableStringification.cpp
@@ -4,7 +4,7 @@
 // and preprocessor token pasting. In other words, hopefully this test
 // will be deleted soon :-)
 
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 #include <catch2/catch_test_macros.hpp>
 
 namespace {
diff --git a/tests/ExtraTests/X90-WindowsHeaderInclusion.cpp b/tests/ExtraTests/X90-WindowsHeaderInclusion.cpp
index 375b66db..454b0a8d 100644
--- a/tests/ExtraTests/X90-WindowsHeaderInclusion.cpp
+++ b/tests/ExtraTests/X90-WindowsHeaderInclusion.cpp
@@ -4,7 +4,7 @@
 // wrong.
 
 #include <windows.h>
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
 #include <catch2/catch_test_macros.hpp>
 
 TEST_CASE("Catch2 did survive compilation with windows.h", "[compile-test]") {
diff --git a/tests/SelfTest/IntrospectiveTests/CmdLine.tests.cpp b/tests/SelfTest/IntrospectiveTests/CmdLine.tests.cpp
index f8d6bd3b..48a297b2 100644
--- a/tests/SelfTest/IntrospectiveTests/CmdLine.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/CmdLine.tests.cpp
@@ -3,14 +3,14 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_approx.h>
+#include <catch2/catch_approx.hpp>
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers_string.hpp>
-#include <catch2/catch_test_spec_parser.h>
-#include <catch2/catch_test_case_info.h>
+#include <catch2/internal/catch_test_spec_parser.hpp>
+#include <catch2/catch_test_case_info.hpp>
 #include <catch2/catch_config.hpp>
-#include <catch2/catch_commandline.h>
-#include <catch2/catch_generators.hpp>
+#include <catch2/internal/catch_commandline.hpp>
+#include <catch2/generators/catch_generators.hpp>
 
 #ifdef __clang__
 #   pragma clang diagnostic ignored "-Wc++98-compat"
diff --git a/tests/SelfTest/IntrospectiveTests/Details.tests.cpp b/tests/SelfTest/IntrospectiveTests/Details.tests.cpp
index 5a24663c..bddb0d5b 100644
--- a/tests/SelfTest/IntrospectiveTests/Details.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/Details.tests.cpp
@@ -4,7 +4,7 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_enforce.h>
+#include <catch2/internal/catch_enforce.hpp>
 
 #if defined(_MSC_VER)
 #pragma warning(push)
diff --git a/tests/SelfTest/IntrospectiveTests/GeneratorsImpl.tests.cpp b/tests/SelfTest/IntrospectiveTests/GeneratorsImpl.tests.cpp
index 459485bc..81fb4ebc 100644
--- a/tests/SelfTest/IntrospectiveTests/GeneratorsImpl.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/GeneratorsImpl.tests.cpp
@@ -1,8 +1,9 @@
-#include <catch2/catch_approx.h>
+#include <catch2/catch_approx.hpp>
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_generator_exception.hpp>
-#include <catch2/catch_generators_generic.hpp>
-#include <catch2/catch_generators_specific.hpp>
+#include <catch2/generators/catch_generator_exception.hpp>
+#include <catch2/generators/catch_generators_adapters.hpp>
+#include <catch2/generators/catch_generators_random.hpp>
+#include <catch2/generators/catch_generators_range.hpp>
 
 // Tests of generator implementation details
 TEST_CASE("Generators internals", "[generators][internals]") {
diff --git a/tests/SelfTest/IntrospectiveTests/InternalBenchmark.tests.cpp b/tests/SelfTest/IntrospectiveTests/InternalBenchmark.tests.cpp
index f9a0a424..50c17169 100644
--- a/tests/SelfTest/IntrospectiveTests/InternalBenchmark.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/InternalBenchmark.tests.cpp
@@ -7,7 +7,7 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_approx.h>
+#include <catch2/catch_approx.hpp>
 #include <catch2/catch_config.hpp>
 #include <catch2/benchmark/catch_benchmark.hpp>
 #include <catch2/benchmark/catch_chronometer.hpp>
diff --git a/tests/SelfTest/IntrospectiveTests/PartTracker.tests.cpp b/tests/SelfTest/IntrospectiveTests/PartTracker.tests.cpp
index b6b4060a..fd40abfa 100644
--- a/tests/SelfTest/IntrospectiveTests/PartTracker.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/PartTracker.tests.cpp
@@ -4,7 +4,7 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_test_case_tracker.h>
+#include <catch2/internal/catch_test_case_tracker.hpp>
 
 
 using namespace Catch;
diff --git a/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp b/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
index f1ff847a..3d388c66 100644
--- a/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
@@ -4,7 +4,7 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_random_number_generator.h>
+#include <catch2/internal/catch_random_number_generator.hpp>
 
 TEST_CASE("Our PCG implementation provides expected results for known seeds", "[rng]") {
     Catch::SimplePcg32 rng;
diff --git a/tests/SelfTest/IntrospectiveTests/String.tests.cpp b/tests/SelfTest/IntrospectiveTests/String.tests.cpp
index 5255804f..ae1cc817 100644
--- a/tests/SelfTest/IntrospectiveTests/String.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/String.tests.cpp
@@ -1,5 +1,5 @@
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_stringref.h>
+#include <catch2/catch_stringref.hpp>
 
 #include <cstring>
 
diff --git a/tests/SelfTest/IntrospectiveTests/StringManip.tests.cpp b/tests/SelfTest/IntrospectiveTests/StringManip.tests.cpp
index 327c8811..d78567ca 100644
--- a/tests/SelfTest/IntrospectiveTests/StringManip.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/StringManip.tests.cpp
@@ -1,6 +1,6 @@
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers_vector.hpp>
-#include <catch2/catch_string_manip.h>
+#include <catch2/internal/catch_string_manip.hpp>
 
 static const char * const no_whitespace = "There is no extra whitespace here";
 static const char * const leading_whitespace = " \r \t\n There is no extra whitespace here";
diff --git a/tests/SelfTest/IntrospectiveTests/Tag.tests.cpp b/tests/SelfTest/IntrospectiveTests/Tag.tests.cpp
index 7765c2fa..15d37c98 100644
--- a/tests/SelfTest/IntrospectiveTests/Tag.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/Tag.tests.cpp
@@ -5,9 +5,9 @@
 
 #include <catch2/matchers/catch_matchers_string.hpp>
 #include <catch2/matchers/catch_matchers_vector.hpp>
-#include <catch2/catch_tag_alias_registry.h>
+#include <catch2/internal/catch_tag_alias_registry.hpp>
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_test_case_info.h>
+#include <catch2/catch_test_case_info.hpp>
 
 TEST_CASE( "Tag alias can be registered against tag patterns" ) {
 
diff --git a/tests/SelfTest/IntrospectiveTests/ToString.tests.cpp b/tests/SelfTest/IntrospectiveTests/ToString.tests.cpp
index d82b5402..966bebed 100644
--- a/tests/SelfTest/IntrospectiveTests/ToString.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/ToString.tests.cpp
@@ -1,4 +1,4 @@
-#include <catch2/catch_enum_values_registry.h>
+#include <catch2/internal/catch_enum_values_registry.hpp>
 #include <catch2/matchers/catch_matchers_vector.hpp>
 #include <catch2/catch_test_macros.hpp>
 
diff --git a/tests/SelfTest/IntrospectiveTests/Xml.tests.cpp b/tests/SelfTest/IntrospectiveTests/Xml.tests.cpp
index b764e3b5..519c3d40 100644
--- a/tests/SelfTest/IntrospectiveTests/Xml.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/Xml.tests.cpp
@@ -1,5 +1,5 @@
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_xmlwriter.h>
+#include <catch2/internal/catch_xmlwriter.hpp>
 
 #include <sstream>
 
diff --git a/tests/SelfTest/TestMain.cpp b/tests/SelfTest/TestMain.cpp
index c7cc5fd0..88025d3a 100644
--- a/tests/SelfTest/TestMain.cpp
+++ b/tests/SelfTest/TestMain.cpp
@@ -3,7 +3,7 @@
  *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  */
 
-#include <catch2/catch_tag_alias_autoregistrar.h>
+#include <catch2/catch_tag_alias_autoregistrar.hpp>
 
 // Some example tag aliases
 CATCH_REGISTER_TAG_ALIAS( "[@nhf]", "[failing]~[.]" )
@@ -25,4 +25,4 @@ struct TestListener : Catch::TestEventListenerBase {
 
 CATCH_REGISTER_LISTENER( TestListener )
 
-#include <catch2/catch_default_main.hpp>
+#include <catch2/internal/catch_default_main.hpp>
diff --git a/tests/SelfTest/UsageTests/Approx.tests.cpp b/tests/SelfTest/UsageTests/Approx.tests.cpp
index 9a1f0474..f0d8919c 100644
--- a/tests/SelfTest/UsageTests/Approx.tests.cpp
+++ b/tests/SelfTest/UsageTests/Approx.tests.cpp
@@ -7,7 +7,7 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_approx.h>
+#include <catch2/catch_approx.hpp>
 
 #include <cmath>
 
diff --git a/tests/SelfTest/UsageTests/Benchmark.tests.cpp b/tests/SelfTest/UsageTests/Benchmark.tests.cpp
index 38ad6a9f..b2d41cf2 100644
--- a/tests/SelfTest/UsageTests/Benchmark.tests.cpp
+++ b/tests/SelfTest/UsageTests/Benchmark.tests.cpp
@@ -1,7 +1,7 @@
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/benchmark/catch_benchmark.hpp>
 #include <catch2/benchmark/catch_constructor.hpp>
-#include <catch2/catch_generators_specific.hpp>
+#include <catch2/generators/catch_generators_range.hpp>
 
 #include <map>
 
diff --git a/tests/SelfTest/UsageTests/Condition.tests.cpp b/tests/SelfTest/UsageTests/Condition.tests.cpp
index 28ca8dd6..7c6a1d73 100644
--- a/tests/SelfTest/UsageTests/Condition.tests.cpp
+++ b/tests/SelfTest/UsageTests/Condition.tests.cpp
@@ -11,7 +11,7 @@
 #   endif
 #endif
 
-#include <catch2/catch_approx.h>
+#include <catch2/catch_approx.hpp>
 #include <catch2/catch_test_macros.hpp>
 
 using Catch::Approx;
diff --git a/tests/SelfTest/UsageTests/EnumToString.tests.cpp b/tests/SelfTest/UsageTests/EnumToString.tests.cpp
index 171e795f..2a6731cb 100644
--- a/tests/SelfTest/UsageTests/EnumToString.tests.cpp
+++ b/tests/SelfTest/UsageTests/EnumToString.tests.cpp
@@ -1,5 +1,5 @@
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_enum_values_registry.h>
+#include <catch2/internal/catch_enum_values_registry.hpp>
 
 
 namespace {
diff --git a/tests/SelfTest/UsageTests/Generators.tests.cpp b/tests/SelfTest/UsageTests/Generators.tests.cpp
index 0b4511c6..45088111 100644
--- a/tests/SelfTest/UsageTests/Generators.tests.cpp
+++ b/tests/SelfTest/UsageTests/Generators.tests.cpp
@@ -1,7 +1,8 @@
 #include <catch2/catch_test_macros.hpp>
-#include <catch2/catch_generator_exception.hpp>
-#include <catch2/catch_generators_generic.hpp>
-#include <catch2/catch_generators_specific.hpp>
+#include <catch2/generators/catch_generator_exception.hpp>
+#include <catch2/generators/catch_generators_adapters.hpp>
+#include <catch2/generators/catch_generators_random.hpp>
+#include <catch2/generators/catch_generators_range.hpp>
 
 #include <cstring>