diff --git a/api/audio_codecs/audio_encoder.h b/api/audio_codecs/audio_encoder.h
index 6a1f6534b2..562b42dd40 100644
--- a/api/audio_codecs/audio_encoder.h
+++ b/api/audio_codecs/audio_encoder.h
@@ -11,7 +11,6 @@
 #ifndef API_AUDIO_CODECS_AUDIO_ENCODER_H_
 #define API_AUDIO_CODECS_AUDIO_ENCODER_H_
 
-#include <algorithm>
 #include <memory>
 #include <string>
 #include <vector>
diff --git a/api/audio_codecs/audio_format.h b/api/audio_codecs/audio_format.h
index aa5dbb13b6..8d28b4f385 100644
--- a/api/audio_codecs/audio_format.h
+++ b/api/audio_codecs/audio_format.h
@@ -13,10 +13,10 @@
 
 #include <map>
 #include <string>
+// TODO(yvesg) Fix presubmit check and/or remove unused swap function.
 #include <utility>
 
 #include "absl/strings/string_view.h"
-#include "absl/types/optional.h"
 #include "rtc_base/checks.h"
 
 namespace webrtc {
diff --git a/api/candidate.cc b/api/candidate.cc
index c2c6c53017..10751ae628 100644
--- a/api/candidate.cc
+++ b/api/candidate.cc
@@ -10,6 +10,7 @@
 
 #include "api/candidate.h"
 
+#include "rtc_base/helpers.h"
 #include "rtc_base/strings/string_builder.h"
 
 namespace cricket {
diff --git a/api/candidate.h b/api/candidate.h
index 6e0547b5e2..0a8459153b 100644
--- a/api/candidate.h
+++ b/api/candidate.h
@@ -18,7 +18,6 @@
 #include <string>
 
 #include "rtc_base/checks.h"
-#include "rtc_base/helpers.h"
 #include "rtc_base/network_constants.h"
 #include "rtc_base/socketaddress.h"
 
diff --git a/api/jsepicecandidate.h b/api/jsepicecandidate.h
index 50520fe727..a57f8618fe 100644
--- a/api/jsepicecandidate.h
+++ b/api/jsepicecandidate.h
@@ -15,7 +15,6 @@
 #define API_JSEPICECANDIDATE_H_
 
 #include <string>
-#include <utility>
 #include <vector>
 
 #include "api/candidate.h"
diff --git a/api/mediaconstraintsinterface.h b/api/mediaconstraintsinterface.h
index c6a914aa56..560fa4a49e 100644
--- a/api/mediaconstraintsinterface.h
+++ b/api/mediaconstraintsinterface.h
@@ -24,7 +24,6 @@
 #include <string>
 #include <vector>
 
-#include "absl/types/optional.h"
 #include "api/peerconnectioninterface.h"
 
 namespace webrtc {
diff --git a/api/mediastreaminterface.h b/api/mediastreaminterface.h
index b661351e9f..2eb2f31d4f 100644
--- a/api/mediastreaminterface.h
+++ b/api/mediastreaminterface.h
@@ -24,17 +24,11 @@
 
 #include "absl/types/optional.h"
 #include "api/video/video_frame.h"
-// TODO(zhihuang): Remove unrelated headers once downstream applications stop
-// relying on them; they were previously transitively included by
-// mediachannel.h, which is no longer a dependency of this file.
 #include "api/video/video_sink_interface.h"
 #include "api/video/video_source_interface.h"
 #include "modules/audio_processing/include/audio_processing_statistics.h"
-#include "rtc_base/ratetracker.h"
 #include "rtc_base/refcount.h"
 #include "rtc_base/scoped_ref_ptr.h"
-#include "rtc_base/thread.h"
-#include "rtc_base/timeutils.h"
 
 namespace webrtc {
 
diff --git a/api/peerconnectioninterface.h b/api/peerconnectioninterface.h
index 1c32b69692..c6850e17ee 100644
--- a/api/peerconnectioninterface.h
+++ b/api/peerconnectioninterface.h
@@ -69,7 +69,6 @@
 
 #include <memory>
 #include <string>
-#include <utility>
 #include <vector>
 
 #include "api/asyncresolverfactory.h"
@@ -79,7 +78,6 @@
 #include "api/audio_options.h"
 #include "api/call/callfactoryinterface.h"
 #include "api/datachannelinterface.h"
-#include "api/dtmfsenderinterface.h"
 #include "api/fec_controller.h"
 #include "api/jsep.h"
 #include "api/mediastreaminterface.h"
@@ -94,7 +92,6 @@
 #include "api/transport/bitrate_settings.h"
 #include "api/transport/network_control.h"
 #include "api/turncustomizer.h"
-#include "api/umametrics.h"
 #include "logging/rtc_event_log/rtc_event_log_factory_interface.h"
 #include "media/base/mediaconfig.h"
 // TODO(bugs.webrtc.org/6353): cricket::VideoCapturer is deprecated and should
diff --git a/api/rtp_headers.cc b/api/rtp_headers.cc
index da7f1ea9fd..bf973b6fe5 100644
--- a/api/rtp_headers.cc
+++ b/api/rtp_headers.cc
@@ -10,14 +10,6 @@
 
 #include "api/rtp_headers.h"
 
-#include <string.h>
-#include <algorithm>
-#include <limits>
-#include <type_traits>
-
-#include "rtc_base/checks.h"
-#include "rtc_base/stringutils.h"
-
 namespace webrtc {
 
 RTPHeaderExtension::RTPHeaderExtension()
diff --git a/api/rtp_headers.h b/api/rtp_headers.h
index 41f39888b8..799058dd1c 100644
--- a/api/rtp_headers.h
+++ b/api/rtp_headers.h
@@ -13,10 +13,7 @@
 
 #include <stddef.h>
 #include <string.h>
-#include <string>
-#include <vector>
 
-#include "absl/types/optional.h"
 #include "api/array_view.h"
 #include "api/video/video_content_type.h"
 #include "api/video/video_frame_marking.h"
@@ -24,8 +21,6 @@
 #include "api/video/video_timing.h"
 
 #include "common_types.h"  // NOLINT(build/include)
-#include "rtc_base/checks.h"
-#include "rtc_base/deprecation.h"
 
 namespace webrtc {
 
diff --git a/api/rtpparameters.cc b/api/rtpparameters.cc
index 98ced9b3ea..e9f4d5d477 100644
--- a/api/rtpparameters.cc
+++ b/api/rtpparameters.cc
@@ -12,7 +12,6 @@
 #include <algorithm>
 #include <string>
 
-#include "rtc_base/checks.h"
 #include "rtc_base/strings/string_builder.h"
 
 namespace webrtc {
diff --git a/api/rtpsenderinterface.h b/api/rtpsenderinterface.h
index 9554c1c4da..7c94c216e6 100644
--- a/api/rtpsenderinterface.h
+++ b/api/rtpsenderinterface.h
@@ -24,7 +24,6 @@
 #include "api/proxy.h"
 #include "api/rtcerror.h"
 #include "api/rtpparameters.h"
-#include "rtc_base/deprecation.h"
 #include "rtc_base/refcount.h"
 #include "rtc_base/scoped_ref_ptr.h"
 
diff --git a/api/video/video_bitrate_allocation.cc b/api/video/video_bitrate_allocation.cc
index 6c5ad1eae5..892253685b 100644
--- a/api/video/video_bitrate_allocation.cc
+++ b/api/video/video_bitrate_allocation.cc
@@ -10,12 +10,9 @@
 
 #include "api/video/video_bitrate_allocation.h"
 
-#include <limits>
-
 #include "rtc_base/checks.h"
 #include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/strings/string_builder.h"
-#include "rtc_base/stringutils.h"
 
 namespace webrtc {
 
diff --git a/api/video/video_content_type.h b/api/video/video_content_type.h
index 8c6460288d..2d38a62366 100644
--- a/api/video/video_content_type.h
+++ b/api/video/video_content_type.h
@@ -13,8 +13,6 @@
 
 #include <stdint.h>
 
-#include <string>
-
 namespace webrtc {
 
 enum class VideoContentType : uint8_t {
diff --git a/audio/channel_send.cc b/audio/channel_send.cc
index d3748b3990..8639fbd814 100644
--- a/audio/channel_send.cc
+++ b/audio/channel_send.cc
@@ -29,6 +29,7 @@
 #include "modules/utility/include/process_thread.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/criticalsection.h"
+#include "rtc_base/event.h"
 #include "rtc_base/format_macros.h"
 #include "rtc_base/location.h"
 #include "rtc_base/logging.h"
diff --git a/audio/null_audio_poller.cc b/audio/null_audio_poller.cc
index c22b3d8791..bd5317ba39 100644
--- a/audio/null_audio_poller.cc
+++ b/audio/null_audio_poller.cc
@@ -11,6 +11,7 @@
 #include "audio/null_audio_poller.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/thread.h"
+#include "rtc_base/timeutils.h"  // for TimeMillis
 
 namespace webrtc {
 namespace internal {
diff --git a/common_video/include/incoming_video_stream.h b/common_video/include/incoming_video_stream.h
index 8063061d31..b32653ba23 100644
--- a/common_video/include/incoming_video_stream.h
+++ b/common_video/include/incoming_video_stream.h
@@ -15,6 +15,7 @@
 #include "common_video/video_render_frames.h"
 #include "rtc_base/race_checker.h"
 #include "rtc_base/task_queue.h"
+#include "rtc_base/thread_checker.h"
 
 namespace webrtc {
 
diff --git a/logging/rtc_event_log/rtc_event_log.h b/logging/rtc_event_log/rtc_event_log.h
index 0c71406902..3a6bc4a0fc 100644
--- a/logging/rtc_event_log/rtc_event_log.h
+++ b/logging/rtc_event_log/rtc_event_log.h
@@ -12,8 +12,6 @@
 #define LOGGING_RTC_EVENT_LOG_RTC_EVENT_LOG_H_
 
 #include <memory>
-#include <string>
-#include <utility>
 
 #include "api/rtceventlogoutput.h"
 #include "logging/rtc_event_log/events/rtc_event.h"
diff --git a/modules/audio_mixer/audio_mixer_impl.h b/modules/audio_mixer/audio_mixer_impl.h
index e8994a674b..8edd3b8bdc 100644
--- a/modules/audio_mixer/audio_mixer_impl.h
+++ b/modules/audio_mixer/audio_mixer_impl.h
@@ -17,6 +17,7 @@
 #include "api/audio/audio_mixer.h"
 #include "modules/audio_mixer/frame_combiner.h"
 #include "modules/audio_mixer/output_rate_calculator.h"
+#include "rtc_base/criticalsection.h"
 #include "rtc_base/race_checker.h"
 #include "rtc_base/scoped_ref_ptr.h"
 #include "rtc_base/thread_annotations.h"
diff --git a/modules/congestion_controller/rtp/send_side_congestion_controller.cc b/modules/congestion_controller/rtp/send_side_congestion_controller.cc
index 266a5dc740..3970f1325b 100644
--- a/modules/congestion_controller/rtp/send_side_congestion_controller.cc
+++ b/modules/congestion_controller/rtp/send_side_congestion_controller.cc
@@ -21,6 +21,7 @@
 #include "modules/remote_bitrate_estimator/include/bwe_defines.h"
 #include "rtc_base/bind.h"
 #include "rtc_base/checks.h"
+#include "rtc_base/event.h"
 #include "rtc_base/format_macros.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/numerics/safe_conversions.h"
diff --git a/modules/rtp_rtcp/source/contributing_sources.h b/modules/rtp_rtcp/source/contributing_sources.h
index 1a4a572d8f..b6201ce794 100644
--- a/modules/rtp_rtcp/source/contributing_sources.h
+++ b/modules/rtp_rtcp/source/contributing_sources.h
@@ -18,7 +18,8 @@
 
 #include "absl/types/optional.h"
 #include "api/array_view.h"
-#include "api/rtpreceiverinterface.h"
+#include "api/rtpreceiverinterface.h"  // For RtpSource
+#include "rtc_base/timeutils.h"        // For kNumMillisecsPerSec
 
 namespace webrtc {
 
diff --git a/p2p/base/stunrequest.cc b/p2p/base/stunrequest.cc
index 56410bea08..7e4d2dceea 100644
--- a/p2p/base/stunrequest.cc
+++ b/p2p/base/stunrequest.cc
@@ -19,6 +19,7 @@
 #include "rtc_base/helpers.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/stringencode.h"
+#include "rtc_base/timeutils.h"  // For TimeMillis
 
 namespace cricket {
 
diff --git a/p2p/base/tcpport_unittest.cc b/p2p/base/tcpport_unittest.cc
index ef302f9026..34385a7f9b 100644
--- a/p2p/base/tcpport_unittest.cc
+++ b/p2p/base/tcpport_unittest.cc
@@ -14,6 +14,7 @@
 #include "p2p/base/basicpacketsocketfactory.h"
 #include "p2p/base/tcpport.h"
 #include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
 #include "rtc_base/thread.h"
 #include "rtc_base/virtualsocketserver.h"
 
diff --git a/pc/peerconnection.cc b/pc/peerconnection.cc
index 6d67329242..f920ddf72c 100644
--- a/pc/peerconnection.cc
+++ b/pc/peerconnection.cc
@@ -22,6 +22,7 @@
 #include "api/jsepsessiondescription.h"
 #include "api/mediastreamproxy.h"
 #include "api/mediastreamtrackproxy.h"
+#include "api/umametrics.h"
 #include "call/call.h"
 #include "logging/rtc_event_log/icelogger.h"
 #include "logging/rtc_event_log/output/rtc_event_log_output_file.h"
diff --git a/pc/peerconnection_ice_unittest.cc b/pc/peerconnection_ice_unittest.cc
index 965956c42a..e6d6ac1550 100644
--- a/pc/peerconnection_ice_unittest.cc
+++ b/pc/peerconnection_ice_unittest.cc
@@ -22,6 +22,7 @@
 #include "api/audio_codecs/builtin_audio_decoder_factory.h"
 #include "api/audio_codecs/builtin_audio_encoder_factory.h"
 #include "api/peerconnectionproxy.h"
+#include "api/umametrics.h"
 #include "api/video_codecs/builtin_video_decoder_factory.h"
 #include "api/video_codecs/builtin_video_encoder_factory.h"
 #include "pc/test/fakeaudiocapturemodule.h"
diff --git a/pc/peerconnection_integrationtest.cc b/pc/peerconnection_integrationtest.cc
index 28e0110355..5825898b1f 100644
--- a/pc/peerconnection_integrationtest.cc
+++ b/pc/peerconnection_integrationtest.cc
@@ -28,6 +28,7 @@
 #include "api/peerconnectioninterface.h"
 #include "api/peerconnectionproxy.h"
 #include "api/rtpreceiverinterface.h"
+#include "api/umametrics.h"
 #include "api/video_codecs/builtin_video_decoder_factory.h"
 #include "api/video_codecs/builtin_video_encoder_factory.h"
 #include "api/video_codecs/sdp_video_format.h"
diff --git a/pc/peerconnection_rtp_unittest.cc b/pc/peerconnection_rtp_unittest.cc
index bc3662cbbd..8453f17481 100644
--- a/pc/peerconnection_rtp_unittest.cc
+++ b/pc/peerconnection_rtp_unittest.cc
@@ -17,6 +17,7 @@
 #include "api/jsep.h"
 #include "api/mediastreaminterface.h"
 #include "api/peerconnectioninterface.h"
+#include "api/umametrics.h"
 #include "api/video_codecs/builtin_video_decoder_factory.h"
 #include "api/video_codecs/builtin_video_encoder_factory.h"
 #include "pc/mediasession.h"
diff --git a/pc/statscollector_unittest.cc b/pc/statscollector_unittest.cc
index fa4d3db81b..7c61b385a9 100644
--- a/pc/statscollector_unittest.cc
+++ b/pc/statscollector_unittest.cc
@@ -22,6 +22,7 @@
 #include "pc/test/fakevideotracksource.h"
 #include "pc/videotrack.h"
 #include "rtc_base/fakesslidentity.h"
+#include "rtc_base/messagedigest.h"
 #include "rtc_base/third_party/base64/base64.h"
 #include "test/gtest.h"
 
diff --git a/pc/videotrack.h b/pc/videotrack.h
index e669e0814c..f119dd86d8 100644
--- a/pc/videotrack.h
+++ b/pc/videotrack.h
@@ -17,6 +17,7 @@
 #include "media/base/videosourcebase.h"
 #include "pc/mediastreamtrack.h"
 #include "rtc_base/scoped_ref_ptr.h"
+#include "rtc_base/thread.h"
 #include "rtc_base/thread_checker.h"
 
 namespace webrtc {
diff --git a/pc/webrtcsdp_unittest.cc b/pc/webrtcsdp_unittest.cc
index 9c10554631..9c39c41751 100644
--- a/pc/webrtcsdp_unittest.cc
+++ b/pc/webrtcsdp_unittest.cc
@@ -22,6 +22,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/gunit.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/messagedigest.h"
 #include "rtc_base/stringencode.h"
 #include "rtc_base/stringutils.h"
 
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index e9efbd1360..5c225a2c39 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -565,7 +565,9 @@ if (rtc_enable_libevent) {
       ":checks",
       ":criticalsection",
       ":logging",
+      ":macromagic",
       ":platform_thread",
+      ":platform_thread_types",
       ":ptr_util",
       ":refcount",
       ":rtc_task_queue_api",
diff --git a/rtc_base/asynctcpsocket.cc b/rtc_base/asynctcpsocket.cc
index 3d68a2a46a..087a98e348 100644
--- a/rtc_base/asynctcpsocket.cc
+++ b/rtc_base/asynctcpsocket.cc
@@ -18,6 +18,7 @@
 #include "rtc_base/byteorder.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/timeutils.h"  // for TimeMillis
 
 #if defined(WEBRTC_POSIX)
 #include <errno.h>
diff --git a/rtc_base/asynctcpsocket.h b/rtc_base/asynctcpsocket.h
index 943e010f4d..c145d6f08f 100644
--- a/rtc_base/asynctcpsocket.h
+++ b/rtc_base/asynctcpsocket.h
@@ -13,10 +13,12 @@
 
 #include <memory>
 
-#include "rtc_base/asyncpacketsocket.h"
-#include "rtc_base/buffer.h"
-#include "rtc_base/constructormagic.h"
-#include "rtc_base/socketfactory.h"
+#include "rtc_base/asyncpacketsocket.h"  // for PacketOptions, AsyncPacketSo...
+#include "rtc_base/asyncsocket.h"        // for AsyncSocket
+#include "rtc_base/buffer.h"             // for Buffer
+#include "rtc_base/constructormagic.h"   // for RTC_DISALLOW_COPY_AND_ASSIGN
+#include "rtc_base/socket.h"             // for Socket, Socket::Option
+#include "rtc_base/socketaddress.h"      // for SocketAddress
 
 namespace rtc {
 
diff --git a/rtc_base/bitrateallocationstrategy.cc b/rtc_base/bitrateallocationstrategy.cc
index d2a06cd9ef..7c65c12373 100644
--- a/rtc_base/bitrateallocationstrategy.cc
+++ b/rtc_base/bitrateallocationstrategy.cc
@@ -10,6 +10,7 @@
 
 #include "rtc_base/bitrateallocationstrategy.h"
 #include <algorithm>
+#include <map>
 #include <utility>
 
 namespace rtc {
diff --git a/rtc_base/bitrateallocationstrategy.h b/rtc_base/bitrateallocationstrategy.h
index f711d1f18f..a4a17f80a3 100644
--- a/rtc_base/bitrateallocationstrategy.h
+++ b/rtc_base/bitrateallocationstrategy.h
@@ -11,12 +11,9 @@
 #ifndef RTC_BASE_BITRATEALLOCATIONSTRATEGY_H_
 #define RTC_BASE_BITRATEALLOCATIONSTRATEGY_H_
 
-#include <map>
-#include <memory>
 #include <string>
 #include <vector>
 #include "api/array_view.h"
-#include "rtc_base/checks.h"
 
 namespace rtc {
 
diff --git a/rtc_base/bytebuffer.cc b/rtc_base/bytebuffer.cc
index 94fc6acf08..f8ce1a29ef 100644
--- a/rtc_base/bytebuffer.cc
+++ b/rtc_base/bytebuffer.cc
@@ -12,8 +12,6 @@
 
 #include <string.h>
 
-#include <algorithm>
-
 namespace rtc {
 
 ByteBufferWriter::ByteBufferWriter() : ByteBufferWriterT() {}
diff --git a/rtc_base/copyonwritebuffer.h b/rtc_base/copyonwritebuffer.h
index 0514e2fe66..177e38f7a7 100644
--- a/rtc_base/copyonwritebuffer.h
+++ b/rtc_base/copyonwritebuffer.h
@@ -16,7 +16,6 @@
 
 #include "rtc_base/buffer.h"
 #include "rtc_base/checks.h"
-#include "rtc_base/refcount.h"
 #include "rtc_base/refcountedobject.h"
 #include "rtc_base/scoped_ref_ptr.h"
 
diff --git a/rtc_base/file.cc b/rtc_base/file.cc
index 62024119fc..a793500646 100644
--- a/rtc_base/file.cc
+++ b/rtc_base/file.cc
@@ -10,8 +10,6 @@
 
 #include "rtc_base/file.h"
 
-#include <utility>
-
 namespace rtc {
 
 File::File(PlatformFile file) : file_(file) {}
diff --git a/rtc_base/filerotatingstream.cc b/rtc_base/filerotatingstream.cc
index c9a663aaff..31b00512d2 100644
--- a/rtc_base/filerotatingstream.cc
+++ b/rtc_base/filerotatingstream.cc
@@ -16,6 +16,7 @@
 
 #include "rtc_base/checks.h"
 #include "rtc_base/fileutils.h"
+#include "rtc_base/logging.h"
 #include "rtc_base/pathutils.h"
 #include "rtc_base/strings/string_builder.h"
 
diff --git a/rtc_base/fileutils.cc b/rtc_base/fileutils.cc
index 7d83f97fae..0adbbac4b0 100644
--- a/rtc_base/fileutils.cc
+++ b/rtc_base/fileutils.cc
@@ -10,12 +10,11 @@
 
 #include "rtc_base/fileutils.h"
 
-#include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/pathutils.h"
-#include "rtc_base/stringutils.h"
 
 #if defined(WEBRTC_WIN)
+#include "rtc_base/stringutils.h"  // for ToUtf16
 #include "rtc_base/win32filesystem.h"
 #else
 #include "rtc_base/unixfilesystem.h"
diff --git a/rtc_base/fileutils.h b/rtc_base/fileutils.h
index 132fd88440..f7afaf9595 100644
--- a/rtc_base/fileutils.h
+++ b/rtc_base/fileutils.h
@@ -23,9 +23,7 @@
 #include <unistd.h>
 #endif  // WEBRTC_WIN
 
-#include "rtc_base/checks.h"
 #include "rtc_base/constructormagic.h"
-#include "rtc_base/platform_file.h"
 
 namespace rtc {
 
diff --git a/rtc_base/flags.cc b/rtc_base/flags.cc
index 5b28794f6c..bcce0dafbc 100644
--- a/rtc_base/flags.cc
+++ b/rtc_base/flags.cc
@@ -15,7 +15,6 @@
 #include <string.h>
 
 #include "rtc_base/checks.h"
-#include "rtc_base/stringutils.h"
 
 #if defined(WEBRTC_WIN)
 // clang-format off
@@ -23,6 +22,8 @@
 #include <windows.h>
 #include <shellapi.h> // must come after windows.h
 // clang-format on
+
+#include "rtc_base/stringutils.h"  // For ToUtf8
 #endif
 
 namespace {
diff --git a/rtc_base/flags.h b/rtc_base/flags.h
index 33f6e5bda1..1c476d80be 100644
--- a/rtc_base/flags.h
+++ b/rtc_base/flags.h
@@ -23,7 +23,10 @@
 #define RTC_BASE_FLAGS_H_
 
 #include "rtc_base/checks.h"
+
+#if defined(WEBRTC_WIN)
 #include "rtc_base/constructormagic.h"
+#endif
 
 namespace rtc {
 
diff --git a/rtc_base/httpcommon.cc b/rtc_base/httpcommon.cc
index 716a41e16e..43831b706f 100644
--- a/rtc_base/httpcommon.cc
+++ b/rtc_base/httpcommon.cc
@@ -18,17 +18,23 @@
 #include <security.h>
 #endif
 
+#include <ctype.h>  // for isspace
+#include <stdio.h>  // for sprintf
 #include <algorithm>
+#include <utility>  // for pair
+#include <vector>
 
 #include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
-#include "rtc_base/cryptstring.h"
+#include "rtc_base/cryptstring.h"  // for CryptString
 #include "rtc_base/httpcommon.h"
+#include "rtc_base/logging.h"
 #include "rtc_base/messagedigest.h"
 #include "rtc_base/socketaddress.h"
 #include "rtc_base/strings/string_builder.h"
-#include "rtc_base/third_party/base64/base64.h"
-#include "rtc_base/zero_memory.h"
+#include "rtc_base/stringutils.h"                // for strcpyn, _stricmp
+#include "rtc_base/third_party/base64/base64.h"  // for Base64
+#include "rtc_base/zero_memory.h"                // for ExplicitZeroMemory
 
 namespace rtc {
 namespace {
diff --git a/rtc_base/httpcommon.h b/rtc_base/httpcommon.h
index 581bd1ee8a..fbad280e02 100644
--- a/rtc_base/httpcommon.h
+++ b/rtc_base/httpcommon.h
@@ -11,14 +11,7 @@
 #ifndef RTC_BASE_HTTPCOMMON_H_
 #define RTC_BASE_HTTPCOMMON_H_
 
-#include <map>
-#include <memory>
 #include <string>
-#include <vector>
-
-#include "rtc_base/checks.h"
-#include "rtc_base/stream.h"
-#include "rtc_base/stringutils.h"
 
 namespace rtc {
 
diff --git a/rtc_base/logging.cc b/rtc_base/logging.cc
index 129a897439..53a1ed849b 100644
--- a/rtc_base/logging.cc
+++ b/rtc_base/logging.cc
@@ -26,7 +26,6 @@
 static const int kMaxLogLineSize = 1024 - 60;
 #endif  // WEBRTC_MAC && !defined(WEBRTC_IOS) || WEBRTC_ANDROID
 
-#include <limits.h>
 #include <time.h>
 
 #include <algorithm>
diff --git a/rtc_base/logging.h b/rtc_base/logging.h
index 1bd0c7205e..5c47c7f7cb 100644
--- a/rtc_base/logging.h
+++ b/rtc_base/logging.h
@@ -60,7 +60,6 @@
 #include "rtc_base/deprecation.h"
 #include "rtc_base/strings/string_builder.h"
 #include "rtc_base/system/inline.h"
-#include "rtc_base/thread_annotations.h"
 
 #if !defined(NDEBUG) || defined(DLOG_ALWAYS_ON)
 #define RTC_DLOG_IS_ON 1
diff --git a/rtc_base/memory/aligned_malloc.cc b/rtc_base/memory/aligned_malloc.cc
index a1d54bdb78..c893c96ef2 100644
--- a/rtc_base/memory/aligned_malloc.cc
+++ b/rtc_base/memory/aligned_malloc.cc
@@ -10,8 +10,8 @@
 
 #include "rtc_base/memory/aligned_malloc.h"
 
-#include <stdlib.h>
-#include <cstring>
+#include <stdlib.h>  // for free, malloc
+#include <string.h>  // for memcpy
 
 #ifdef _WIN32
 #include <windows.h>
diff --git a/rtc_base/messagehandler.h b/rtc_base/messagehandler.h
index df2d1ada8d..0c40853e21 100644
--- a/rtc_base/messagehandler.h
+++ b/rtc_base/messagehandler.h
@@ -11,7 +11,6 @@
 #ifndef RTC_BASE_MESSAGEHANDLER_H_
 #define RTC_BASE_MESSAGEHANDLER_H_
 
-#include <memory>
 #include <utility>
 
 #include "rtc_base/constructormagic.h"
diff --git a/rtc_base/messagequeue.cc b/rtc_base/messagequeue.cc
index a561af42eb..84d3a96eb8 100644
--- a/rtc_base/messagequeue.cc
+++ b/rtc_base/messagequeue.cc
@@ -8,13 +8,14 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #include <algorithm>
+#include <utility>  // for move
 
 #include "rtc_base/atomicops.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/messagequeue.h"
-#include "rtc_base/stringencode.h"
 #include "rtc_base/thread.h"
+#include "rtc_base/timeutils.h"  // for TimeMillis, TimeDiff, TimeUntil
 #include "rtc_base/trace_event.h"
 
 namespace rtc {
diff --git a/rtc_base/messagequeue.h b/rtc_base/messagequeue.h
index e7e479285d..c1b9b5a916 100644
--- a/rtc_base/messagequeue.h
+++ b/rtc_base/messagequeue.h
@@ -17,7 +17,6 @@
 #include <list>
 #include <memory>
 #include <queue>
-#include <utility>
 #include <vector>
 
 #include "rtc_base/constructormagic.h"
@@ -28,7 +27,6 @@
 #include "rtc_base/socketserver.h"
 #include "rtc_base/third_party/sigslot/sigslot.h"
 #include "rtc_base/thread_annotations.h"
-#include "rtc_base/timeutils.h"
 
 namespace rtc {
 
diff --git a/rtc_base/nethelper.h b/rtc_base/nethelper.h
index e86d126cbf..f9561380fb 100644
--- a/rtc_base/nethelper.h
+++ b/rtc_base/nethelper.h
@@ -10,7 +10,6 @@
 #ifndef RTC_BASE_NETHELPER_H_
 #define RTC_BASE_NETHELPER_H_
 
-#include <cstdlib>
 #include <string>
 
 // This header contains helper functions and constants used by different types
diff --git a/rtc_base/nethelpers.cc b/rtc_base/nethelpers.cc
index b1221c3d00..81cd1afcef 100644
--- a/rtc_base/nethelpers.cc
+++ b/rtc_base/nethelpers.cc
@@ -25,10 +25,9 @@
 #endif
 #endif  // defined(WEBRTC_POSIX) && !defined(__native_client__)
 
-#include "rtc_base/byteorder.h"
-#include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/signalthread.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"  // for signal_with_thread...
 
 namespace rtc {
 
diff --git a/rtc_base/nethelpers.h b/rtc_base/nethelpers.h
index f9d188f61d..429f0c0c74 100644
--- a/rtc_base/nethelpers.h
+++ b/rtc_base/nethelpers.h
@@ -18,12 +18,12 @@
 #include <winsock2.h>  // NOLINT
 #endif
 
-#include <list>
+#include <vector>
 
 #include "rtc_base/asyncresolverinterface.h"
+#include "rtc_base/ipaddress.h"  // for IPAddress
 #include "rtc_base/signalthread.h"
 #include "rtc_base/socketaddress.h"
-#include "rtc_base/third_party/sigslot/sigslot.h"
 
 namespace rtc {
 
diff --git a/rtc_base/networkmonitor.cc b/rtc_base/networkmonitor.cc
index ad6805acec..e3b2efde22 100644
--- a/rtc_base/networkmonitor.cc
+++ b/rtc_base/networkmonitor.cc
@@ -11,6 +11,7 @@
 #include "rtc_base/networkmonitor.h"
 
 #include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
 
 namespace {
 const uint32_t UPDATE_NETWORKS_MESSAGE = 1;
diff --git a/rtc_base/networkmonitor.h b/rtc_base/networkmonitor.h
index a84a30aed2..1ad7663669 100644
--- a/rtc_base/networkmonitor.h
+++ b/rtc_base/networkmonitor.h
@@ -11,7 +11,6 @@
 #ifndef RTC_BASE_NETWORKMONITOR_H_
 #define RTC_BASE_NETWORKMONITOR_H_
 
-#include "rtc_base/logging.h"
 #include "rtc_base/network_constants.h"
 #include "rtc_base/third_party/sigslot/sigslot.h"
 #include "rtc_base/thread.h"
diff --git a/rtc_base/openssladapter.cc b/rtc_base/openssladapter.cc
index 50284a6719..b5891952dc 100644
--- a/rtc_base/openssladapter.cc
+++ b/rtc_base/openssladapter.cc
@@ -23,6 +23,7 @@
 #include <openssl/x509v3.h>
 #include "rtc_base/openssl.h"
 
+#include "absl/memory/memory.h"  // for make_unique
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/numerics/safe_conversions.h"
diff --git a/rtc_base/openssladapter.h b/rtc_base/openssladapter.h
index 50a7c0845c..45ffc6f0dc 100644
--- a/rtc_base/openssladapter.h
+++ b/rtc_base/openssladapter.h
@@ -13,19 +13,22 @@
 
 #include <openssl/ossl_typ.h>
 
-#include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
-#include "absl/memory/memory.h"
-#include "rtc_base/buffer.h"
-#include "rtc_base/messagehandler.h"
-#include "rtc_base/messagequeue.h"
-#include "rtc_base/opensslcertificate.h"
-#include "rtc_base/opensslidentity.h"
-#include "rtc_base/opensslsessioncache.h"
-#include "rtc_base/ssladapter.h"
+#include "rtc_base/asyncsocket.h"          // for AsyncSocket
+#include "rtc_base/buffer.h"               // for Buffer
+#include "rtc_base/messagehandler.h"       // for MessageHandler
+#include "rtc_base/messagequeue.h"         // for Message
+#include "rtc_base/opensslidentity.h"      // for SSL_CTX, OpenSSLIdentity
+#include "rtc_base/opensslsessioncache.h"  // for OpenSSLSessionCache
+#include "rtc_base/socket.h"               // for Socket::ConnState
+#include "rtc_base/socketaddress.h"        // for SocketAddress
+#include "rtc_base/ssladapter.h"           // for SSLAdapter, SSLAdapterFactory
+#include "rtc_base/sslcertificate.h"       // for SSLCertificateVerifier
+#include "rtc_base/sslidentity.h"          // for SSLIdentity
+#include "rtc_base/sslstreamadapter.h"     // for SSLMode, SSLRole, SSL_MODE...
 
 namespace rtc {
 
diff --git a/rtc_base/opensslcertificate.h b/rtc_base/opensslcertificate.h
index c730ffd0dc..b7ecc3b78d 100644
--- a/rtc_base/opensslcertificate.h
+++ b/rtc_base/opensslcertificate.h
@@ -11,16 +11,16 @@
 #ifndef RTC_BASE_OPENSSLCERTIFICATE_H_
 #define RTC_BASE_OPENSSLCERTIFICATE_H_
 
-#include <openssl/evp.h>
-#include <openssl/x509.h>
+#include <openssl/base.h>  // for X509, ssl_ctx_st
 
-#include <memory>
+#include <stddef.h>  // for size_t
+#include <stdint.h>  // for int64_t
 #include <string>
 
-#include "rtc_base/checks.h"
-#include "rtc_base/constructormagic.h"
-#include "rtc_base/sslcertificate.h"
-#include "rtc_base/sslidentity.h"
+#include "rtc_base/buffer.h"            // for Buffer
+#include "rtc_base/constructormagic.h"  // for RTC_DISALLOW_COPY_AND_ASSIGN
+#include "rtc_base/sslcertificate.h"    // for SSLCertificate
+#include "rtc_base/sslidentity.h"       // for SSLIdentityParams
 
 typedef struct ssl_ctx_st SSL_CTX;
 
diff --git a/rtc_base/openssldigest.h b/rtc_base/openssldigest.h
index c4cd1e0314..1427a94fdd 100644
--- a/rtc_base/openssldigest.h
+++ b/rtc_base/openssldigest.h
@@ -11,7 +11,8 @@
 #ifndef RTC_BASE_OPENSSLDIGEST_H_
 #define RTC_BASE_OPENSSLDIGEST_H_
 
-#include <openssl/evp.h>
+#include <openssl/base.h>  // for EVP_MD, EVP_MD_CTX
+#include <string>
 
 #include "rtc_base/messagedigest.h"
 
diff --git a/rtc_base/opensslidentity.h b/rtc_base/opensslidentity.h
index 34044276ca..b72a4c2294 100644
--- a/rtc_base/opensslidentity.h
+++ b/rtc_base/opensslidentity.h
@@ -11,16 +11,17 @@
 #ifndef RTC_BASE_OPENSSLIDENTITY_H_
 #define RTC_BASE_OPENSSLIDENTITY_H_
 
-#include <openssl/evp.h>
-#include <openssl/x509.h>
+#include <openssl/base.h>  // for EVP_PKEY, ssl_ctx_st
 
-#include <memory>
+#include <ctime>   // for time_t
+#include <memory>  // for unique_ptr
 #include <string>
 
-#include "rtc_base/checks.h"
-#include "rtc_base/constructormagic.h"
-#include "rtc_base/opensslcertificate.h"
-#include "rtc_base/sslidentity.h"
+#include "rtc_base/checks.h"              // for RTC_DCHECK
+#include "rtc_base/constructormagic.h"    // for RTC_DISALLOW_COPY_AND_ASSIGN
+#include "rtc_base/opensslcertificate.h"  // for OpenSSLCertificate
+#include "rtc_base/sslcertificate.h"      // for SSLCertChain
+#include "rtc_base/sslidentity.h"         // for SSLIdentity, KeyParams, SSL...
 
 typedef struct ssl_ctx_st SSL_CTX;
 
diff --git a/rtc_base/opensslutility.h b/rtc_base/opensslutility.h
index 7cb38b5b52..77ed0b1e7c 100644
--- a/rtc_base/opensslutility.h
+++ b/rtc_base/opensslutility.h
@@ -13,7 +13,6 @@
 
 #include <openssl/ossl_typ.h>
 #include <string>
-#include "rtc_base/sslcertificate.h"
 
 namespace rtc {
 // The openssl namespace holds static helper methods. All methods related
diff --git a/rtc_base/pathutils.cc b/rtc_base/pathutils.cc
index 594deb7f0f..07646716c2 100644
--- a/rtc_base/pathutils.cc
+++ b/rtc_base/pathutils.cc
@@ -15,10 +15,9 @@
 #include <tchar.h>
 #endif  // WEBRTC_WIN
 
-#include "rtc_base/checks.h"
-#include "rtc_base/logging.h"
+#include <string.h>  // for strchr
+
 #include "rtc_base/pathutils.h"
-#include "rtc_base/stringutils.h"
 
 namespace rtc {
 
diff --git a/rtc_base/pathutils.h b/rtc_base/pathutils.h
index 9543be073f..59f2a4ac29 100644
--- a/rtc_base/pathutils.h
+++ b/rtc_base/pathutils.h
@@ -13,8 +13,6 @@
 
 #include <string>
 
-#include "rtc_base/checks.h"
-
 namespace rtc {
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/rtc_base/platform_file.cc b/rtc_base/platform_file.cc
index a4c906a1ed..d74acddd02 100644
--- a/rtc_base/platform_file.cc
+++ b/rtc_base/platform_file.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/platform_file.h"
 
-#include "rtc_base/stringutils.h"
-
 #if defined(WEBRTC_WIN)
 #include <io.h>
+#include "rtc_base/stringutils.h"  // For ToUtf16
 #else
 #include <fcntl.h>
 #include <sys/stat.h>
diff --git a/rtc_base/platform_thread.h b/rtc_base/platform_thread.h
index 33921c209d..ea67aca42b 100644
--- a/rtc_base/platform_thread.h
+++ b/rtc_base/platform_thread.h
@@ -14,7 +14,6 @@
 #include <string>
 
 #include "rtc_base/constructormagic.h"
-#include "rtc_base/event.h"
 #include "rtc_base/platform_thread_types.h"
 #include "rtc_base/thread_checker.h"
 
diff --git a/rtc_base/proxyserver.cc b/rtc_base/proxyserver.cc
index 55cab80975..71c4879099 100644
--- a/rtc_base/proxyserver.cc
+++ b/rtc_base/proxyserver.cc
@@ -13,6 +13,7 @@
 #include <algorithm>
 
 #include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
 #include "rtc_base/socketfactory.h"
 
 namespace rtc {
diff --git a/rtc_base/race_checker.h b/rtc_base/race_checker.h
index 73567e98d8..d6eba08276 100644
--- a/rtc_base/race_checker.h
+++ b/rtc_base/race_checker.h
@@ -12,7 +12,7 @@
 #define RTC_BASE_RACE_CHECKER_H_
 
 #include "rtc_base/checks.h"
-#include "rtc_base/platform_thread.h"
+#include "rtc_base/platform_thread_types.h"  // for PlatformThreadRef
 #include "rtc_base/thread_annotations.h"
 
 namespace rtc {
diff --git a/rtc_base/ratetracker.cc b/rtc_base/ratetracker.cc
index e31d26627a..7c96ca9f60 100644
--- a/rtc_base/ratetracker.cc
+++ b/rtc_base/ratetracker.cc
@@ -10,8 +10,6 @@
 
 #include "rtc_base/ratetracker.h"
 
-#include <stddef.h>
-
 #include <algorithm>
 
 #include "rtc_base/checks.h"
diff --git a/rtc_base/rtccertificate.cc b/rtc_base/rtccertificate.cc
index 7f027ba5f8..786333fcc3 100644
--- a/rtc_base/rtccertificate.cc
+++ b/rtc_base/rtccertificate.cc
@@ -14,6 +14,7 @@
 
 #include "rtc_base/checks.h"
 #include "rtc_base/refcountedobject.h"
+#include "rtc_base/timeutils.h"
 
 namespace rtc {
 
diff --git a/rtc_base/sequenced_task_checker_unittest.cc b/rtc_base/sequenced_task_checker_unittest.cc
index 96e655baad..83fb14f964 100644
--- a/rtc_base/sequenced_task_checker_unittest.cc
+++ b/rtc_base/sequenced_task_checker_unittest.cc
@@ -12,6 +12,7 @@
 
 #include "rtc_base/checks.h"
 #include "rtc_base/constructormagic.h"
+#include "rtc_base/event.h"
 #include "rtc_base/platform_thread.h"
 #include "rtc_base/task_queue.h"
 #include "rtc_base/thread_checker.h"
diff --git a/rtc_base/signalthread.cc b/rtc_base/signalthread.cc
index eb79dc84fe..2e0fa0cb6b 100644
--- a/rtc_base/signalthread.cc
+++ b/rtc_base/signalthread.cc
@@ -12,6 +12,7 @@
 
 #include "absl/memory/memory.h"
 #include "rtc_base/checks.h"
+#include "rtc_base/nullsocketserver.h"
 
 namespace rtc {
 
diff --git a/rtc_base/signalthread.h b/rtc_base/signalthread.h
index 021cf4d78d..448b2890e5 100644
--- a/rtc_base/signalthread.h
+++ b/rtc_base/signalthread.h
@@ -14,10 +14,13 @@
 #include <string>
 
 #include "rtc_base/checks.h"
-#include "rtc_base/constructormagic.h"
-#include "rtc_base/nullsocketserver.h"
-#include "rtc_base/third_party/sigslot/sigslot.h"
-#include "rtc_base/thread.h"
+#include "rtc_base/constructormagic.h"             // for RTC_DISALLOW_IMPLI...
+#include "rtc_base/criticalsection.h"              // for CriticalSection
+#include "rtc_base/messagehandler.h"               // for MessageHandler
+#include "rtc_base/messagequeue.h"                 // for Message
+#include "rtc_base/third_party/sigslot/sigslot.h"  // for has_slots, signal_...
+#include "rtc_base/thread.h"                       // for Thread
+#include "rtc_base/thread_annotations.h"           // for RTC_EXCLUSIVE_LOCK...
 
 namespace rtc {
 
diff --git a/rtc_base/socketadapters.cc b/rtc_base/socketadapters.cc
index acd9b63385..98be868db6 100644
--- a/rtc_base/socketadapters.cc
+++ b/rtc_base/socketadapters.cc
@@ -30,7 +30,6 @@
 #include "rtc_base/httpcommon.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/socketadapters.h"
-#include "rtc_base/stringencode.h"
 #include "rtc_base/strings/string_builder.h"
 #include "rtc_base/stringutils.h"
 #include "rtc_base/zero_memory.h"
diff --git a/rtc_base/socketadapters.h b/rtc_base/socketadapters.h
index ad88fe6b6f..062f75c3fe 100644
--- a/rtc_base/socketadapters.h
+++ b/rtc_base/socketadapters.h
@@ -11,13 +11,11 @@
 #ifndef RTC_BASE_SOCKETADAPTERS_H_
 #define RTC_BASE_SOCKETADAPTERS_H_
 
-#include <map>
 #include <string>
 
 #include "rtc_base/asyncsocket.h"
 #include "rtc_base/constructormagic.h"
 #include "rtc_base/cryptstring.h"
-#include "rtc_base/logging.h"
 
 namespace rtc {
 
diff --git a/rtc_base/socketaddress.h b/rtc_base/socketaddress.h
index bff8e76495..b1a52b9371 100644
--- a/rtc_base/socketaddress.h
+++ b/rtc_base/socketaddress.h
@@ -15,7 +15,6 @@
 #ifdef UNIT_TEST
 #include <ostream>  // no-presubmit-check TODO(webrtc:8982)
 #endif              // UNIT_TEST
-#include <vector>
 #include "rtc_base/ipaddress.h"
 
 #undef SetPort
diff --git a/rtc_base/ssladapter_unittest.cc b/rtc_base/ssladapter_unittest.cc
index ec532b1c44..8ed460f21e 100644
--- a/rtc_base/ssladapter_unittest.cc
+++ b/rtc_base/ssladapter_unittest.cc
@@ -15,6 +15,7 @@
 #include "absl/memory/memory.h"
 #include "rtc_base/gunit.h"
 #include "rtc_base/ipaddress.h"
+#include "rtc_base/messagedigest.h"
 #include "rtc_base/socketstream.h"
 #include "rtc_base/ssladapter.h"
 #include "rtc_base/sslidentity.h"
diff --git a/rtc_base/sslcertificate.cc b/rtc_base/sslcertificate.cc
index 9a38fc0384..e40feec219 100644
--- a/rtc_base/sslcertificate.cc
+++ b/rtc_base/sslcertificate.cc
@@ -10,16 +10,15 @@
 
 #include "rtc_base/sslcertificate.h"
 
-#include <ctime>
+#include <algorithm>  // for transform
 #include <string>
 #include <utility>
 
-#include "absl/memory/memory.h"
-#include "rtc_base/checks.h"
-#include "rtc_base/logging.h"
-#include "rtc_base/opensslcertificate.h"
-#include "rtc_base/sslfingerprint.h"
-#include "rtc_base/third_party/base64/base64.h"
+#include "absl/memory/memory.h"                  // for WrapUnique, make_unique
+#include "rtc_base/checks.h"                     // for FatalLogCall, RTC_DC...
+#include "rtc_base/opensslcertificate.h"         // for OpenSSLCertificate
+#include "rtc_base/sslfingerprint.h"             // for SSLFingerprint
+#include "rtc_base/third_party/base64/base64.h"  // for Base64
 
 namespace rtc {
 
diff --git a/rtc_base/sslcertificate.h b/rtc_base/sslcertificate.h
index 29c4db58ef..029404cf3e 100644
--- a/rtc_base/sslcertificate.h
+++ b/rtc_base/sslcertificate.h
@@ -15,15 +15,12 @@
 #ifndef RTC_BASE_SSLCERTIFICATE_H_
 #define RTC_BASE_SSLCERTIFICATE_H_
 
-#include <algorithm>
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "rtc_base/buffer.h"
 #include "rtc_base/constructormagic.h"
-#include "rtc_base/messagedigest.h"
-#include "rtc_base/timeutils.h"
 
 namespace rtc {
 
diff --git a/rtc_base/sslfingerprint.cc b/rtc_base/sslfingerprint.cc
index b651a3d628..4f1ae8f7a5 100644
--- a/rtc_base/sslfingerprint.cc
+++ b/rtc_base/sslfingerprint.cc
@@ -13,7 +13,6 @@
 #include <ctype.h>
 #include <string>
 
-#include "rtc_base/helpers.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/messagedigest.h"
 #include "rtc_base/stringencode.h"
diff --git a/rtc_base/sslidentity.cc b/rtc_base/sslidentity.cc
index 823fc388a3..1d136d7298 100644
--- a/rtc_base/sslidentity.cc
+++ b/rtc_base/sslidentity.cc
@@ -11,17 +11,15 @@
 // Handling of certificates and keypairs for SSLStreamAdapter's peer mode.
 #include "rtc_base/sslidentity.h"
 
+#include <string.h>  // for strspn
 #include <ctime>
 #include <string>
-#include <utility>
 
-#include "absl/memory/memory.h"
-#include "rtc_base/checks.h"
-#include "rtc_base/logging.h"
-#include "rtc_base/opensslidentity.h"
-#include "rtc_base/sslfingerprint.h"
-#include "rtc_base/strings/string_builder.h"
-#include "rtc_base/third_party/base64/base64.h"
+#include "rtc_base/checks.h"                     // for FatalLogCall, RTC_DC...
+#include "rtc_base/opensslidentity.h"            // for OpenSSLIdentity
+#include "rtc_base/strings/string_builder.h"     // for StringBuilder
+#include "rtc_base/third_party/base64/base64.h"  // for Base64, Base64::DO_P...
+#include "rtc_base/timeutils.h"                  // for TmToSeconds
 
 namespace rtc {
 
diff --git a/rtc_base/sslidentity.h b/rtc_base/sslidentity.h
index 1379d733be..d17d38bacd 100644
--- a/rtc_base/sslidentity.h
+++ b/rtc_base/sslidentity.h
@@ -13,16 +13,10 @@
 #ifndef RTC_BASE_SSLIDENTITY_H_
 #define RTC_BASE_SSLIDENTITY_H_
 
-#include <algorithm>
-#include <memory>
+#include <ctime>
 #include <string>
-#include <vector>
 
-#include "rtc_base/buffer.h"
-#include "rtc_base/constructormagic.h"
-#include "rtc_base/messagedigest.h"
 #include "rtc_base/sslcertificate.h"
-#include "rtc_base/timeutils.h"
 
 namespace rtc {
 
diff --git a/rtc_base/sslidentity_unittest.cc b/rtc_base/sslidentity_unittest.cc
index 132e240c2f..68b582839f 100644
--- a/rtc_base/sslidentity_unittest.cc
+++ b/rtc_base/sslidentity_unittest.cc
@@ -14,6 +14,7 @@
 #include "rtc_base/fakesslidentity.h"
 #include "rtc_base/gunit.h"
 #include "rtc_base/helpers.h"
+#include "rtc_base/messagedigest.h"
 #include "rtc_base/ssladapter.h"
 #include "rtc_base/sslfingerprint.h"
 #include "rtc_base/sslidentity.h"
diff --git a/rtc_base/sslstreamadapter_unittest.cc b/rtc_base/sslstreamadapter_unittest.cc
index 3403bdbe72..389b0eaaf1 100644
--- a/rtc_base/sslstreamadapter_unittest.cc
+++ b/rtc_base/sslstreamadapter_unittest.cc
@@ -17,6 +17,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/gunit.h"
 #include "rtc_base/helpers.h"
+#include "rtc_base/messagedigest.h"
 #include "rtc_base/ssladapter.h"
 #include "rtc_base/sslidentity.h"
 #include "rtc_base/sslstreamadapter.h"
diff --git a/rtc_base/stream.cc b/rtc_base/stream.cc
index d1ec1400de..ea2e47a6fb 100644
--- a/rtc_base/stream.cc
+++ b/rtc_base/stream.cc
@@ -15,21 +15,20 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 
+#include <string.h>  // for memcpy, memmove, strlen
 #include <algorithm>
 #include <string>
 
 #include "rtc_base/checks.h"
-#include "rtc_base/logging.h"
+#include "rtc_base/location.h"  // for RTC_FROM_HERE
 #include "rtc_base/messagequeue.h"
 #include "rtc_base/stream.h"
-#include "rtc_base/stringencode.h"
-#include "rtc_base/stringutils.h"
 #include "rtc_base/thread.h"
-#include "rtc_base/timeutils.h"
 
 #if defined(WEBRTC_WIN)
 #include <windows.h>
 #define fileno _fileno
+#include "rtc_base/stringutils.h"  // for ToUtf16
 #endif
 
 namespace rtc {
diff --git a/rtc_base/stream.h b/rtc_base/stream.h
index 81c5e41801..7c6e618e28 100644
--- a/rtc_base/stream.h
+++ b/rtc_base/stream.h
@@ -18,7 +18,6 @@
 #include "rtc_base/buffer.h"
 #include "rtc_base/constructormagic.h"
 #include "rtc_base/criticalsection.h"
-#include "rtc_base/logging.h"
 #include "rtc_base/messagehandler.h"
 #include "rtc_base/messagequeue.h"
 #include "rtc_base/third_party/sigslot/sigslot.h"
diff --git a/rtc_base/stringencode.cc b/rtc_base/stringencode.cc
index a57845ffda..6a065cb8b2 100644
--- a/rtc_base/stringencode.cc
+++ b/rtc_base/stringencode.cc
@@ -10,9 +10,6 @@
 
 #include "rtc_base/stringencode.h"
 
-#include <stdio.h>
-#include <stdlib.h>
-
 #include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/stringutils.h"
diff --git a/rtc_base/strings/string_builder.cc b/rtc_base/strings/string_builder.cc
index 2fd4aba19c..0dca938a1e 100644
--- a/rtc_base/strings/string_builder.cc
+++ b/rtc_base/strings/string_builder.cc
@@ -10,6 +10,12 @@
 
 #include "rtc_base/strings/string_builder.h"
 
+#include <stdarg.h>  // for va_end, va_list, va_start
+#include <cstring>   // for strlen
+
+#include "rtc_base/checks.h"                // for FatalLogCall, RTC_DCHECK
+#include "rtc_base/numerics/safe_minmax.h"  // for SafeMin
+
 namespace rtc {
 
 SimpleStringBuilder::SimpleStringBuilder(rtc::ArrayView<char> buffer)
diff --git a/rtc_base/strings/string_builder.h b/rtc_base/strings/string_builder.h
index 186c2f7b9d..27001d1be5 100644
--- a/rtc_base/strings/string_builder.h
+++ b/rtc_base/strings/string_builder.h
@@ -12,13 +12,11 @@
 #define RTC_BASE_STRINGS_STRING_BUILDER_H_
 
 #include <cstdio>
-#include <cstring>
 #include <string>
+#include <utility>
 
 #include "absl/strings/string_view.h"
 #include "api/array_view.h"
-#include "rtc_base/checks.h"
-#include "rtc_base/numerics/safe_minmax.h"
 #include "rtc_base/stringencode.h"
 #include "rtc_base/stringutils.h"
 
diff --git a/rtc_base/stringutils.cc b/rtc_base/stringutils.cc
index 6baddd11bd..35153ab813 100644
--- a/rtc_base/stringutils.cc
+++ b/rtc_base/stringutils.cc
@@ -7,11 +7,10 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
-#include <algorithm>
-#include <cstdio>
+
+#include "rtc_base/stringutils.h"
 
 #include "rtc_base/checks.h"
-#include "rtc_base/stringutils.h"
 
 namespace rtc {
 
diff --git a/rtc_base/task_queue_libevent.cc b/rtc_base/task_queue_libevent.cc
index d3b1a7c5cb..ce05bae137 100644
--- a/rtc_base/task_queue_libevent.cc
+++ b/rtc_base/task_queue_libevent.cc
@@ -10,11 +10,17 @@
 
 #include "rtc_base/task_queue.h"
 
+#include <errno.h>  // for EAGAIN, errno
 #include <fcntl.h>
+#include <pthread.h>  // for pthread_getspecific
 #include <signal.h>
-#include <string.h>
+#include <stdint.h>  // for uint32_t
+#include <time.h>    // for nanosleep, timespec
 #include <unistd.h>
 #include <list>
+#include <memory>       // for unique_ptr, allocator
+#include <type_traits>  // for remove_reference<>::...
+#include <utility>      // for move
 
 #include "base/third_party/libevent/event.h"
 #include "rtc_base/checks.h"
@@ -22,11 +28,13 @@
 #include "rtc_base/logging.h"
 #include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/platform_thread.h"
+#include "rtc_base/platform_thread_types.h"  // for CurrentThreadRef
 #include "rtc_base/refcount.h"
 #include "rtc_base/refcountedobject.h"
+#include "rtc_base/scoped_ref_ptr.h"  // for scoped_refptr
 #include "rtc_base/system/unused.h"
-#include "rtc_base/task_queue.h"
 #include "rtc_base/task_queue_posix.h"
+#include "rtc_base/thread_annotations.h"  // for RTC_GUARDED_BY
 #include "rtc_base/timeutils.h"
 
 namespace rtc {
diff --git a/rtc_base/third_party/sigslot/sigslot.h b/rtc_base/third_party/sigslot/sigslot.h
index c77e4e675d..8bd1c7064a 100644
--- a/rtc_base/third_party/sigslot/sigslot.h
+++ b/rtc_base/third_party/sigslot/sigslot.h
@@ -96,7 +96,6 @@
 #ifndef RTC_BASE_THIRD_PARTY_SIGSLOT_SIGSLOT_H_
 #define RTC_BASE_THIRD_PARTY_SIGSLOT_SIGSLOT_H_
 
-#include <stdlib.h>
 #include <cstring>
 #include <list>
 #include <set>
diff --git a/rtc_base/thread.cc b/rtc_base/thread.cc
index 2d5704e0be..911ac16b07 100644
--- a/rtc_base/thread.cc
+++ b/rtc_base/thread.cc
@@ -24,10 +24,11 @@
 #pragma warning(disable : 4722)
 #endif
 
+#include <utility>  // for move
+
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/nullsocketserver.h"
-#include "rtc_base/platform_thread.h"
 #include "rtc_base/stringutils.h"
 #include "rtc_base/timeutils.h"
 #include "rtc_base/trace_event.h"
diff --git a/rtc_base/thread.h b/rtc_base/thread.h
index 5a466104aa..fde5e8bf39 100644
--- a/rtc_base/thread.h
+++ b/rtc_base/thread.h
@@ -11,12 +11,9 @@
 #ifndef RTC_BASE_THREAD_H_
 #define RTC_BASE_THREAD_H_
 
-#include <algorithm>
 #include <list>
 #include <memory>
 #include <string>
-#include <utility>
-#include <vector>
 
 #if defined(WEBRTC_POSIX)
 #include <pthread.h>
diff --git a/rtc_base/thread_darwin.mm b/rtc_base/thread_darwin.mm
index a404849c72..e64d6ebe0b 100644
--- a/rtc_base/thread_darwin.mm
+++ b/rtc_base/thread_darwin.mm
@@ -13,6 +13,7 @@
 #import <Foundation/Foundation.h>
 
 #include "rtc_base/platform_thread.h"
+#include "rtc_base/timeutils.h"  // for TimeAfter, TimeUntil
 
 /*
  * This file contains platform-specific implementations for several
diff --git a/rtc_base/unixfilesystem.cc b/rtc_base/unixfilesystem.cc
index 023c34c8c9..818cb8a9d7 100644
--- a/rtc_base/unixfilesystem.cc
+++ b/rtc_base/unixfilesystem.cc
@@ -47,6 +47,7 @@
 #include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/fileutils.h"
+#include "rtc_base/logging.h"
 #include "rtc_base/pathutils.h"
 #include "rtc_base/stream.h"
 #include "rtc_base/stringutils.h"
diff --git a/rtc_base/win32filesystem.cc b/rtc_base/win32filesystem.cc
index b500e5e629..cd439660db 100644
--- a/rtc_base/win32filesystem.cc
+++ b/rtc_base/win32filesystem.cc
@@ -20,6 +20,7 @@
 #include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/fileutils.h"
+#include "rtc_base/logging.h"
 #include "rtc_base/pathutils.h"
 #include "rtc_base/stream.h"
 #include "rtc_base/stringutils.h"
diff --git a/rtc_base/win32socketserver.cc b/rtc_base/win32socketserver.cc
index cab751a631..230f3ed46f 100644
--- a/rtc_base/win32socketserver.cc
+++ b/rtc_base/win32socketserver.cc
@@ -16,6 +16,7 @@
 #include "rtc_base/byteorder.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/timeutils.h"  // For Time, TimeSince
 #include "rtc_base/win32window.h"
 
 namespace rtc {
diff --git a/sdk/android/BUILD.gn b/sdk/android/BUILD.gn
index 64aece08e4..9a319aba75 100644
--- a/sdk/android/BUILD.gn
+++ b/sdk/android/BUILD.gn
@@ -830,6 +830,7 @@ if (is_android) {
       ":videoframe_jni",
       "//api:libjingle_peerconnection_api",
       "//api/video:video_frame",
+      "//rtc_base:rtc_base",
       "//rtc_base:rtc_base_approved",
       "//third_party/abseil-cpp/absl/memory",
     ]
diff --git a/sdk/android/native_api/video/videosource.h b/sdk/android/native_api/video/videosource.h
index 0c4f33342e..11d983d71d 100644
--- a/sdk/android/native_api/video/videosource.h
+++ b/sdk/android/native_api/video/videosource.h
@@ -14,6 +14,7 @@
 #include <jni.h>
 
 #include "api/mediastreaminterface.h"
+#include "rtc_base/thread.h"
 #include "sdk/android/native_api/jni/scoped_java_ref.h"
 
 namespace webrtc {
diff --git a/sdk/android/src/jni/androidnetworkmonitor.cc b/sdk/android/src/jni/androidnetworkmonitor.cc
index b1351ef1e1..7ac17281f9 100644
--- a/sdk/android/src/jni/androidnetworkmonitor.cc
+++ b/sdk/android/src/jni/androidnetworkmonitor.cc
@@ -19,6 +19,7 @@
 #include "rtc_base/bind.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/ipaddress.h"
+#include "rtc_base/logging.h"
 #include "rtc_base/strings/string_builder.h"
 #include "sdk/android/generated_base_jni/jni/NetworkMonitorAutoDetect_jni.h"
 #include "sdk/android/generated_base_jni/jni/NetworkMonitor_jni.h"
diff --git a/sdk/objc/api/peerconnection/RTCVideoSource+Private.h b/sdk/objc/api/peerconnection/RTCVideoSource+Private.h
index 2441e0cdbe..828aad87bd 100644
--- a/sdk/objc/api/peerconnection/RTCVideoSource+Private.h
+++ b/sdk/objc/api/peerconnection/RTCVideoSource+Private.h
@@ -13,6 +13,7 @@
 #import "RTCMediaSource+Private.h"
 
 #include "api/mediastreaminterface.h"
+#include "rtc_base/thread.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
diff --git a/sdk/objc/native/api/video_capturer.h b/sdk/objc/native/api/video_capturer.h
index 5b6f3f939b..d6f396b470 100644
--- a/sdk/objc/native/api/video_capturer.h
+++ b/sdk/objc/native/api/video_capturer.h
@@ -15,6 +15,7 @@
 
 #include "api/mediastreaminterface.h"
 #include "rtc_base/scoped_ref_ptr.h"
+#include "rtc_base/thread.h"
 
 namespace webrtc {
 
diff --git a/test/scenario/BUILD.gn b/test/scenario/BUILD.gn
index 3703aa84e7..24d4bfdcba 100644
--- a/test/scenario/BUILD.gn
+++ b/test/scenario/BUILD.gn
@@ -82,6 +82,7 @@ if (rtc_include_tests) {
       "../../rtc_base:rtc_base_approved",
       "../../rtc_base:rtc_base_tests_utils",
       "../../rtc_base:rtc_task_queue",
+      "../../rtc_base:safe_minmax",
       "../../rtc_base:sequenced_task_checker",
       "../../rtc_base:stringutils",
       "../../system_wrappers",
diff --git a/test/scenario/network_node.cc b/test/scenario/network_node.cc
index ff138939ab..ec841091d9 100644
--- a/test/scenario/network_node.cc
+++ b/test/scenario/network_node.cc
@@ -12,6 +12,8 @@
 #include <algorithm>
 #include <vector>
 
+#include "rtc_base/numerics/safe_minmax.h"
+
 namespace webrtc {
 namespace test {
 namespace {