diff --git a/api/array_view_unittest.cc b/api/array_view_unittest.cc
index 445f418..f424cd2 100644
--- a/api/array_view_unittest.cc
+++ b/api/array_view_unittest.cc
@@ -10,10 +10,9 @@
 
 #include "api/array_view.h"
 
-#include <stdint.h>
-
 #include <array>
 #include <cstddef>
+#include <cstdint>
 #include <string>
 #include <utility>
 #include <vector>
diff --git a/api/audio/audio_frame.cc b/api/audio/audio_frame.cc
index c6a8936..78b84efc 100644
--- a/api/audio/audio_frame.cc
+++ b/api/audio/audio_frame.cc
@@ -10,9 +10,8 @@
 
 #include "api/audio/audio_frame.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <optional>
 
 #include "api/array_view.h"
diff --git a/api/audio/channel_layout.cc b/api/audio/channel_layout.cc
index 596db90..9e6dcc3 100644
--- a/api/audio/channel_layout.cc
+++ b/api/audio/channel_layout.cc
@@ -10,8 +10,7 @@
 
 #include "api/audio/channel_layout.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <iterator>
 
 #include "rtc_base/checks.h"
diff --git a/api/audio/test/audio_frame_unittest.cc b/api/audio/test/audio_frame_unittest.cc
index 4397716..9ee422e 100644
--- a/api/audio/test/audio_frame_unittest.cc
+++ b/api/audio/test/audio_frame_unittest.cc
@@ -10,8 +10,8 @@
 
 #include "api/audio/audio_frame.h"
 
-#include <stdint.h>
-#include <string.h>  // memcmp
+#include <cstdint>
+#include <cstring>
 
 #include "api/audio/audio_view.h"
 #include "api/audio/channel_layout.h"
diff --git a/api/audio_codecs/L16/audio_encoder_L16.cc b/api/audio_codecs/L16/audio_encoder_L16.cc
index 458f680..71372bd 100644
--- a/api/audio_codecs/L16/audio_encoder_L16.cc
+++ b/api/audio_codecs/L16/audio_encoder_L16.cc
@@ -10,8 +10,7 @@
 
 #include "api/audio_codecs/L16/audio_encoder_L16.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <map>
 #include <memory>
 #include <optional>
diff --git a/api/audio_codecs/g711/audio_encoder_g711.cc b/api/audio_codecs/g711/audio_encoder_g711.cc
index f430bbc..af8f1ea 100644
--- a/api/audio_codecs/g711/audio_encoder_g711.cc
+++ b/api/audio_codecs/g711/audio_encoder_g711.cc
@@ -10,8 +10,7 @@
 
 #include "api/audio_codecs/g711/audio_encoder_g711.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <initializer_list>
 #include <map>
 #include <memory>
diff --git a/api/audio_codecs/g722/audio_encoder_g722.cc b/api/audio_codecs/g722/audio_encoder_g722.cc
index ed86d16..d1bbb2e 100644
--- a/api/audio_codecs/g722/audio_encoder_g722.cc
+++ b/api/audio_codecs/g722/audio_encoder_g722.cc
@@ -10,8 +10,7 @@
 
 #include "api/audio_codecs/g722/audio_encoder_g722.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <map>
 #include <memory>
 #include <optional>
diff --git a/api/legacy_stats_types.cc b/api/legacy_stats_types.cc
index 64e8d42..c7dae1c 100644
--- a/api/legacy_stats_types.cc
+++ b/api/legacy_stats_types.cc
@@ -10,9 +10,8 @@
 
 #include "api/legacy_stats_types.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <string>
 #include <utility>
 
diff --git a/api/numerics/samples_stats_counter_unittest.cc b/api/numerics/samples_stats_counter_unittest.cc
index d1614f2..a713bb1 100644
--- a/api/numerics/samples_stats_counter_unittest.cc
+++ b/api/numerics/samples_stats_counter_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "api/numerics/samples_stats_counter.h"
 
-#include <math.h>
-
+#include <cmath>
 #include <random>
 #include <vector>
 
diff --git a/api/rtc_event_log_output_file_unittest.cc b/api/rtc_event_log_output_file_unittest.cc
index b1441c7..38b8b47 100644
--- a/api/rtc_event_log_output_file_unittest.cc
+++ b/api/rtc_event_log_output_file_unittest.cc
@@ -13,6 +13,7 @@
 #include <stdio.h>
 
 #include <cstddef>
+#include <cstdio>
 #include <fstream>
 #include <ios>
 #include <iterator>
diff --git a/api/rtp_packet_info.cc b/api/rtp_packet_info.cc
index 90cd275..557247b 100644
--- a/api/rtp_packet_info.cc
+++ b/api/rtp_packet_info.cc
@@ -10,9 +10,8 @@
 
 #include "api/rtp_packet_info.h"
 
-#include <stddef.h>
-
 #include <algorithm>
+#include <cstddef>
 #include <cstdint>
 #include <utility>
 #include <vector>
diff --git a/api/rtp_packet_infos_unittest.cc b/api/rtp_packet_infos_unittest.cc
index 544bb93..e05ed66 100644
--- a/api/rtp_packet_infos_unittest.cc
+++ b/api/rtp_packet_infos_unittest.cc
@@ -10,7 +10,7 @@
 
 #include "api/rtp_packet_infos.h"
 
-#include <stddef.h>
+#include <cstddef>
 
 #include "api/rtp_headers.h"
 #include "api/rtp_packet_info.h"
diff --git a/api/test/metrics/chrome_perf_dashboard_metrics_exporter.cc b/api/test/metrics/chrome_perf_dashboard_metrics_exporter.cc
index 5fe0b14..79d50d6 100644
--- a/api/test/metrics/chrome_perf_dashboard_metrics_exporter.cc
+++ b/api/test/metrics/chrome_perf_dashboard_metrics_exporter.cc
@@ -9,8 +9,7 @@
  */
 #include "api/test/metrics/chrome_perf_dashboard_metrics_exporter.h"
 
-#include <stdio.h>
-
+#include <cstdio>
 #include <memory>
 #include <string>
 #include <vector>
diff --git a/api/test/metrics/metrics_set_proto_file_exporter.cc b/api/test/metrics/metrics_set_proto_file_exporter.cc
index 044828c..c3a7554 100644
--- a/api/test/metrics/metrics_set_proto_file_exporter.cc
+++ b/api/test/metrics/metrics_set_proto_file_exporter.cc
@@ -9,8 +9,7 @@
  */
 #include "api/test/metrics/metrics_set_proto_file_exporter.h"
 
-#include <stdio.h>
-
+#include <cstdio>
 #include <map>
 #include <string>
 #include <utility>
diff --git a/api/test/metrics/stdout_metrics_exporter.cc b/api/test/metrics/stdout_metrics_exporter.cc
index 62b8ad8..52ae291 100644
--- a/api/test/metrics/stdout_metrics_exporter.cc
+++ b/api/test/metrics/stdout_metrics_exporter.cc
@@ -9,10 +9,9 @@
  */
 #include "api/test/metrics/stdout_metrics_exporter.h"
 
-#include <stdio.h>
-
 #include <cmath>
 #include <cstdint>
+#include <cstdio>
 #include <optional>
 #include <string>
 
diff --git a/api/video/encoded_image.cc b/api/video/encoded_image.cc
index 163250a..f09bb23 100644
--- a/api/video/encoded_image.cc
+++ b/api/video/encoded_image.cc
@@ -10,9 +10,8 @@
 
 #include "api/video/encoded_image.h"
 
-#include <stdlib.h>
-
 #include <cstdint>
+#include <cstdlib>
 #include <optional>
 #include <utility>
 
diff --git a/api/video/i410_buffer.cc b/api/video/i410_buffer.cc
index 37564b9..a09a5a5 100644
--- a/api/video/i410_buffer.cc
+++ b/api/video/i410_buffer.cc
@@ -9,10 +9,9 @@
  */
 #include "api/video/i410_buffer.h"
 
-#include <string.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 #include <utility>
 
 #include "api/make_ref_counted.h"
diff --git a/api/video/i420_buffer.cc b/api/video/i420_buffer.cc
index 33b2ea6..e9320ce 100644
--- a/api/video/i420_buffer.cc
+++ b/api/video/i420_buffer.cc
@@ -9,10 +9,9 @@
  */
 #include "api/video/i420_buffer.h"
 
-#include <string.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 #include <utility>
 
 #include "api/make_ref_counted.h"
diff --git a/api/video/i422_buffer.cc b/api/video/i422_buffer.cc
index 25814a8..fb6dd34 100644
--- a/api/video/i422_buffer.cc
+++ b/api/video/i422_buffer.cc
@@ -9,10 +9,9 @@
  */
 #include "api/video/i422_buffer.h"
 
-#include <string.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 #include <utility>
 
 #include "api/make_ref_counted.h"
diff --git a/api/video/i444_buffer.cc b/api/video/i444_buffer.cc
index ace6af1..452777e 100644
--- a/api/video/i444_buffer.cc
+++ b/api/video/i444_buffer.cc
@@ -9,10 +9,9 @@
  */
 #include "api/video/i444_buffer.h"
 
-#include <string.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 #include <utility>
 
 #include "api/make_ref_counted.h"
diff --git a/api/video/test/color_space_unittest.cc b/api/video/test/color_space_unittest.cc
index ae66b01..55714f2 100644
--- a/api/video/test/color_space_unittest.cc
+++ b/api/video/test/color_space_unittest.cc
@@ -10,7 +10,7 @@
 
 #include "api/video/color_space.h"
 
-#include <stdint.h>
+#include <cstdint>
 
 #include "test/gtest.h"
 
diff --git a/api/video_codecs/test/video_decoder_software_fallback_wrapper_unittest.cc b/api/video_codecs/test/video_decoder_software_fallback_wrapper_unittest.cc
index 67d847f..493dc1f 100644
--- a/api/video_codecs/test/video_decoder_software_fallback_wrapper_unittest.cc
+++ b/api/video_codecs/test/video_decoder_software_fallback_wrapper_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "api/video_codecs/video_decoder_software_fallback_wrapper.h"
 
-#include <stdint.h>
-
+#include <cstdint>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/api/video_codecs/test/video_encoder_software_fallback_wrapper_unittest.cc b/api/video_codecs/test/video_encoder_software_fallback_wrapper_unittest.cc
index bb987a6..bdb388e 100644
--- a/api/video_codecs/test/video_encoder_software_fallback_wrapper_unittest.cc
+++ b/api/video_codecs/test/video_encoder_software_fallback_wrapper_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "api/video_codecs/video_encoder_software_fallback_wrapper.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
+#include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/api/video_codecs/video_codec.cc b/api/video_codecs/video_codec.cc
index 7ebe029..e032439 100644
--- a/api/video_codecs/video_codec.cc
+++ b/api/video_codecs/video_codec.cc
@@ -10,8 +10,7 @@
 
 #include "api/video_codecs/video_codec.h"
 
-#include <string.h>
-
+#include <cstring>
 #include <string>
 
 #include "absl/strings/match.h"
diff --git a/api/video_codecs/video_decoder_software_fallback_wrapper.cc b/api/video_codecs/video_decoder_software_fallback_wrapper.cc
index 5d5eeaa..ffb151e 100644
--- a/api/video_codecs/video_decoder_software_fallback_wrapper.cc
+++ b/api/video_codecs/video_decoder_software_fallback_wrapper.cc
@@ -10,9 +10,8 @@
 
 #include "api/video_codecs/video_decoder_software_fallback_wrapper.h"
 
-#include <stdint.h>
-
 #include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <string>
 #include <utility>
diff --git a/api/video_codecs/video_encoder.cc b/api/video_codecs/video_encoder.cc
index fcbb250..d549e87 100644
--- a/api/video_codecs/video_encoder.cc
+++ b/api/video_codecs/video_encoder.cc
@@ -10,10 +10,9 @@
 
 #include "api/video_codecs/video_encoder.h"
 
-#include <string.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 #include <optional>
 #include <string>
 #include <tuple>
diff --git a/api/video_codecs/video_encoder_software_fallback_wrapper.cc b/api/video_codecs/video_encoder_software_fallback_wrapper.cc
index e1b7910..f2ed055 100644
--- a/api/video_codecs/video_encoder_software_fallback_wrapper.cc
+++ b/api/video_codecs/video_encoder_software_fallback_wrapper.cc
@@ -10,8 +10,7 @@
 
 #include "api/video_codecs/video_encoder_software_fallback_wrapper.h"
 
-#include <stdint.h>
-
+#include <cstdint>
 #include <cstdio>
 #include <memory>
 #include <numeric>
diff --git a/pc/audio_rtp_receiver.cc b/pc/audio_rtp_receiver.cc
index 10bd129..328207d 100644
--- a/pc/audio_rtp_receiver.cc
+++ b/pc/audio_rtp_receiver.cc
@@ -10,8 +10,7 @@
 
 #include "pc/audio_rtp_receiver.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <optional>
 #include <string>
diff --git a/pc/channel_unittest.cc b/pc/channel_unittest.cc
index 5d4071d..d49afef 100644
--- a/pc/channel_unittest.cc
+++ b/pc/channel_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "pc/channel.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <optional>
diff --git a/pc/codec_vendor.cc b/pc/codec_vendor.cc
index 42d52f6..7c5d335 100644
--- a/pc/codec_vendor.cc
+++ b/pc/codec_vendor.cc
@@ -9,9 +9,8 @@
  */
 #include "pc/codec_vendor.h"
 
-#include <stddef.h>
-
 #include <algorithm>
+#include <cstddef>
 #include <map>
 #include <optional>
 #include <string>
diff --git a/pc/codec_vendor_unittest.cc b/pc/codec_vendor_unittest.cc
index 8dd99f2..22fe53a 100644
--- a/pc/codec_vendor_unittest.cc
+++ b/pc/codec_vendor_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "pc/codec_vendor.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <string>
 #include <vector>
 
diff --git a/pc/data_channel_integrationtest.cc b/pc/data_channel_integrationtest.cc
index 9eb0d22..03111a3 100644
--- a/pc/data_channel_integrationtest.cc
+++ b/pc/data_channel_integrationtest.cc
@@ -8,9 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stdint.h>
-
 #include <atomic>
+#include <cstdint>
 #include <cstdlib>
 #include <iterator>
 #include <memory>
diff --git a/pc/data_channel_unittest.cc b/pc/data_channel_unittest.cc
index 9b4802a..603b7f9 100644
--- a/pc/data_channel_unittest.cc
+++ b/pc/data_channel_unittest.cc
@@ -8,9 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stdint.h>
-#include <string.h>
-
+#include <cstdint>
+#include <cstring>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/dtls_srtp_transport_unittest.cc b/pc/dtls_srtp_transport_unittest.cc
index 1101ab2..40108df 100644
--- a/pc/dtls_srtp_transport_unittest.cc
+++ b/pc/dtls_srtp_transport_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "pc/dtls_srtp_transport.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <vector>
 
diff --git a/pc/dtmf_sender.cc b/pc/dtmf_sender.cc
index 6ecc285..703fe9b 100644
--- a/pc/dtmf_sender.cc
+++ b/pc/dtmf_sender.cc
@@ -10,10 +10,9 @@
 
 #include "pc/dtmf_sender.h"
 
-#include <ctype.h>
-#include <string.h>
-
+#include <cctype>
 #include <cstdint>
+#include <cstring>
 #include <string>
 
 #include "api/dtmf_sender_interface.h"
diff --git a/pc/dtmf_sender_unittest.cc b/pc/dtmf_sender_unittest.cc
index 82b149b..deb18fe 100644
--- a/pc/dtmf_sender_unittest.cc
+++ b/pc/dtmf_sender_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "pc/dtmf_sender.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <string>
diff --git a/pc/external_hmac.cc b/pc/external_hmac.cc
index 77f11a3..a0ee51b 100644
--- a/pc/external_hmac.cc
+++ b/pc/external_hmac.cc
@@ -10,10 +10,9 @@
 
 #include "pc/external_hmac.h"
 
-#include <stdlib.h>  // For malloc/free.
-#include <string.h>
-
 #include <cstdint>
+#include <cstdlib>
+#include <cstring>
 
 #include "rtc_base/logging.h"
 #include "rtc_base/zero_memory.h"
diff --git a/pc/ice_server_parsing.cc b/pc/ice_server_parsing.cc
index ee3b446..58bc996 100644
--- a/pc/ice_server_parsing.cc
+++ b/pc/ice_server_parsing.cc
@@ -10,9 +10,8 @@
 
 #include "pc/ice_server_parsing.h"
 
-#include <stddef.h>
-
-#include <cctype>  // For std::isdigit.
+#include <cctype>
+#include <cstddef>
 #include <optional>
 #include <string>
 #include <tuple>
diff --git a/pc/jsep_session_description_unittest.cc b/pc/jsep_session_description_unittest.cc
index 5960d58..2f99dfd 100644
--- a/pc/jsep_session_description_unittest.cc
+++ b/pc/jsep_session_description_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "api/jsep_session_description.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
+#include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <string>
 #include <utility>
diff --git a/pc/jsep_transport.cc b/pc/jsep_transport.cc
index b1f179c..91b123c 100644
--- a/pc/jsep_transport.cc
+++ b/pc/jsep_transport.cc
@@ -10,9 +10,8 @@
 
 #include "pc/jsep_transport.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
+#include <cstddef>
+#include <cstdint>
 #include <functional>
 #include <memory>
 #include <optional>
@@ -34,6 +33,7 @@
 #include "p2p/base/p2p_constants.h"
 #include "p2p/base/p2p_transport_channel.h"
 #include "p2p/base/transport_description.h"
+#include "p2p/dtls/dtls_transport_internal.h"
 #include "pc/dtls_srtp_transport.h"
 #include "pc/dtls_transport.h"
 #include "pc/rtp_transport.h"
diff --git a/pc/jsep_transport_controller.cc b/pc/jsep_transport_controller.cc
index 77c1d91..f3095d7 100644
--- a/pc/jsep_transport_controller.cc
+++ b/pc/jsep_transport_controller.cc
@@ -10,8 +10,7 @@
 
 #include "pc/jsep_transport_controller.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <functional>
 #include <map>
diff --git a/pc/jsep_transport_unittest.cc b/pc/jsep_transport_unittest.cc
index 06bf6fd..48a4147 100644
--- a/pc/jsep_transport_unittest.cc
+++ b/pc/jsep_transport_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "pc/jsep_transport.h"
 
-#include <stdint.h>
-#include <string.h>
-
+#include <cstdint>
+#include <cstring>
 #include <memory>
 #include <optional>
 #include <ostream>
diff --git a/pc/legacy_stats_collector.cc b/pc/legacy_stats_collector.cc
index e871468..fd230f1 100644
--- a/pc/legacy_stats_collector.cc
+++ b/pc/legacy_stats_collector.cc
@@ -10,11 +10,10 @@
 
 #include "pc/legacy_stats_collector.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
 #include <algorithm>
 #include <cmath>
+#include <cstddef>
+#include <cstdint>
 #include <map>
 #include <memory>
 #include <optional>
diff --git a/pc/legacy_stats_collector_unittest.cc b/pc/legacy_stats_collector_unittest.cc
index 36d9a49..c5e0b1a 100644
--- a/pc/legacy_stats_collector_unittest.cc
+++ b/pc/legacy_stats_collector_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "pc/legacy_stats_collector.h"
 
-#include <stdio.h>
-
 #include <cstdint>
+#include <cstdio>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/media_protocol_names.cc b/pc/media_protocol_names.cc
index d2416cd..65123dc 100644
--- a/pc/media_protocol_names.cc
+++ b/pc/media_protocol_names.cc
@@ -10,11 +10,12 @@
 
 #include "pc/media_protocol_names.h"
 
-#include <ctype.h>
-#include <stddef.h>
-
+#include <cctype>
+#include <cstddef>
 #include <string>
 
+#include "absl/strings/string_view.h"
+
 namespace webrtc {
 
 // The official registry of RTP parameters is at
diff --git a/pc/media_session.cc b/pc/media_session.cc
index 12a6c0f..38dcebe 100644
--- a/pc/media_session.cc
+++ b/pc/media_session.cc
@@ -10,9 +10,8 @@
 
 #include "pc/media_session.h"
 
-#include <stddef.h>
-
 #include <algorithm>
+#include <cstddef>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/media_session_unittest.cc b/pc/media_session_unittest.cc
index 0501ef0..6de8f34 100644
--- a/pc/media_session_unittest.cc
+++ b/pc/media_session_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "pc/media_session.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <map>
 #include <memory>
diff --git a/pc/media_stream.cc b/pc/media_stream.cc
index ceafb52..e4f5235 100644
--- a/pc/media_stream.cc
+++ b/pc/media_stream.cc
@@ -10,8 +10,7 @@
 
 #include "pc/media_stream.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <string>
 #include <utility>
 
diff --git a/pc/media_stream_unittest.cc b/pc/media_stream_unittest.cc
index 35a518f..de82b20 100644
--- a/pc/media_stream_unittest.cc
+++ b/pc/media_stream_unittest.cc
@@ -10,7 +10,7 @@
 
 #include "pc/media_stream.h"
 
-#include <stddef.h>
+#include <cstddef>
 
 #include "api/media_stream_interface.h"
 #include "api/scoped_refptr.h"
diff --git a/pc/peer_connection.cc b/pc/peer_connection.cc
index 0c9394c..bf267df 100644
--- a/pc/peer_connection.cc
+++ b/pc/peer_connection.cc
@@ -10,9 +10,8 @@
 
 #include "pc/peer_connection.h"
 
-#include <limits.h>
-#include <stddef.h>
-
+#include <climits>
+#include <cstddef>
 #include <cstdint>
 #include <functional>
 #include <map>
diff --git a/pc/peer_connection_adaptation_integrationtest.cc b/pc/peer_connection_adaptation_integrationtest.cc
index da4f387..cdb8ea8 100644
--- a/pc/peer_connection_adaptation_integrationtest.cc
+++ b/pc/peer_connection_adaptation_integrationtest.cc
@@ -8,8 +8,6 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stdint.h>
-
 #include <memory>
 #include <optional>
 
diff --git a/pc/peer_connection_bundle_unittest.cc b/pc/peer_connection_bundle_unittest.cc
index 83481a4..b0de320 100644
--- a/pc/peer_connection_bundle_unittest.cc
+++ b/pc/peer_connection_bundle_unittest.cc
@@ -8,8 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <memory>
 #include <ostream>
 #include <string>
diff --git a/pc/peer_connection_crypto_unittest.cc b/pc/peer_connection_crypto_unittest.cc
index f3591ed..215e7ad 100644
--- a/pc/peer_connection_crypto_unittest.cc
+++ b/pc/peer_connection_crypto_unittest.cc
@@ -8,8 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <memory>
 #include <ostream>
 #include <string>
diff --git a/pc/peer_connection_end_to_end_unittest.cc b/pc/peer_connection_end_to_end_unittest.cc
index 32c0b9a..fccedba 100644
--- a/pc/peer_connection_end_to_end_unittest.cc
+++ b/pc/peer_connection_end_to_end_unittest.cc
@@ -8,9 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stdint.h>
-
 #include <cstddef>
+#include <cstdint>
 #include <limits>
 #include <memory>
 #include <optional>
diff --git a/pc/peer_connection_ice_unittest.cc b/pc/peer_connection_ice_unittest.cc
index fb7aea2..f9a9e34 100644
--- a/pc/peer_connection_ice_unittest.cc
+++ b/pc/peer_connection_ice_unittest.cc
@@ -8,9 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stddef.h>
-#include <stdint.h>
-
+#include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/peer_connection_integrationtest.cc b/pc/peer_connection_integrationtest.cc
index 41abef4..ca61b6a 100644
--- a/pc/peer_connection_integrationtest.cc
+++ b/pc/peer_connection_integrationtest.cc
@@ -15,10 +15,9 @@
 // do NOT add it here, but instead add it to the file
 // slow_peer_connection_integrationtest.cc
 
-#include <stdint.h>
-
 #include <algorithm>
 #include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/peer_connection_interface_unittest.cc b/pc/peer_connection_interface_unittest.cc
index 08f192b..35c4df3 100644
--- a/pc/peer_connection_interface_unittest.cc
+++ b/pc/peer_connection_interface_unittest.cc
@@ -10,10 +10,9 @@
 
 #include "api/peer_connection_interface.h"
 
-#include <limits.h>
-#include <stdint.h>
-
+#include <climits>
 #include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/peer_connection_jsep_unittest.cc b/pc/peer_connection_jsep_unittest.cc
index dfcd5df..eb3922a 100644
--- a/pc/peer_connection_jsep_unittest.cc
+++ b/pc/peer_connection_jsep_unittest.cc
@@ -8,9 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stddef.h>
-
 #include <algorithm>
+#include <cstddef>
 #include <map>
 #include <memory>
 #include <optional>
diff --git a/pc/peer_connection_rtp_unittest.cc b/pc/peer_connection_rtp_unittest.cc
index 43d7455..41f630d 100644
--- a/pc/peer_connection_rtp_unittest.cc
+++ b/pc/peer_connection_rtp_unittest.cc
@@ -8,8 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <optional>
diff --git a/pc/peer_connection_stability_integrationtest.cc b/pc/peer_connection_stability_integrationtest.cc
index 61c6ba0..8d30522 100644
--- a/pc/peer_connection_stability_integrationtest.cc
+++ b/pc/peer_connection_stability_integrationtest.cc
@@ -14,8 +14,6 @@
 // The error messages when the tests fail are intended to contain C++ code
 // that can be pasted into the test when updating it.
 
-#include <stdint.h>
-
 #include <algorithm>
 #include <memory>
 #include <string>
diff --git a/pc/peer_connection_svc_integrationtest.cc b/pc/peer_connection_svc_integrationtest.cc
index 9e61012..3fae4e8 100644
--- a/pc/peer_connection_svc_integrationtest.cc
+++ b/pc/peer_connection_svc_integrationtest.cc
@@ -11,8 +11,6 @@
 // Integration tests for PeerConnection.
 // These tests exercise a full stack for the SVC extension.
 
-#include <stdint.h>
-
 #include <algorithm>
 #include <vector>
 
diff --git a/pc/peer_connection_wrapper.cc b/pc/peer_connection_wrapper.cc
index f6e10f7..35fa45a 100644
--- a/pc/peer_connection_wrapper.cc
+++ b/pc/peer_connection_wrapper.cc
@@ -10,8 +10,6 @@
 
 #include "pc/peer_connection_wrapper.h"
 
-#include <stdint.h>
-
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/remote_audio_source.cc b/pc/remote_audio_source.cc
index 706c7f4..82eb9ae 100644
--- a/pc/remote_audio_source.cc
+++ b/pc/remote_audio_source.cc
@@ -10,8 +10,7 @@
 
 #include "pc/remote_audio_source.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <optional>
diff --git a/pc/rtc_stats_collector_unittest.cc b/pc/rtc_stats_collector_unittest.cc
index 77a9ebb..8686354 100644
--- a/pc/rtc_stats_collector_unittest.cc
+++ b/pc/rtc_stats_collector_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "pc/rtc_stats_collector.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
+#include <cstddef>
+#include <cstdint>
 #include <initializer_list>
 #include <map>
 #include <memory>
diff --git a/pc/rtc_stats_integrationtest.cc b/pc/rtc_stats_integrationtest.cc
index 2e3b69d..f2e92dd 100644
--- a/pc/rtc_stats_integrationtest.cc
+++ b/pc/rtc_stats_integrationtest.cc
@@ -8,8 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stdint.h>
-
+#include <cstdint>
 #include <memory>
 #include <optional>
 #include <set>
diff --git a/pc/rtp_receiver.cc b/pc/rtp_receiver.cc
index e09c893..31a20df 100644
--- a/pc/rtp_receiver.cc
+++ b/pc/rtp_receiver.cc
@@ -10,9 +10,8 @@
 
 #include "pc/rtp_receiver.h"
 
-#include <stddef.h>
-
 #include <atomic>
+#include <cstddef>
 #include <string>
 #include <utility>
 #include <vector>
diff --git a/pc/rtp_sender_receiver_unittest.cc b/pc/rtp_sender_receiver_unittest.cc
index 5b32de7..7ff31ba 100644
--- a/pc/rtp_sender_receiver_unittest.cc
+++ b/pc/rtp_sender_receiver_unittest.cc
@@ -8,8 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <iterator>
 #include <memory>
diff --git a/pc/rtp_transceiver.cc b/pc/rtp_transceiver.cc
index dadc9de..4697da8 100644
--- a/pc/rtp_transceiver.cc
+++ b/pc/rtp_transceiver.cc
@@ -10,9 +10,8 @@
 
 #include "pc/rtp_transceiver.h"
 
-#include <stdint.h>
-
 #include <cstddef>
+#include <cstdint>
 #include <functional>
 #include <iterator>
 #include <memory>
diff --git a/pc/rtp_transport.cc b/pc/rtp_transport.cc
index e2f5cdf..c8a91e7 100644
--- a/pc/rtp_transport.cc
+++ b/pc/rtp_transport.cc
@@ -10,8 +10,7 @@
 
 #include "pc/rtp_transport.h"
 
-#include <errno.h>
-
+#include <cerrno>
 #include <cstdint>
 #include <optional>
 #include <string>
diff --git a/pc/sctp_utils.cc b/pc/sctp_utils.cc
index edf1572..49cdb71 100644
--- a/pc/sctp_utils.cc
+++ b/pc/sctp_utils.cc
@@ -10,8 +10,7 @@
 
 #include "pc/sctp_utils.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <optional>
 #include <string>
diff --git a/pc/sctp_utils_unittest.cc b/pc/sctp_utils_unittest.cc
index 5e7d099..df02229 100644
--- a/pc/sctp_utils_unittest.cc
+++ b/pc/sctp_utils_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "pc/sctp_utils.h"
 
-#include <stdint.h>
-
+#include <cstdint>
 #include <limits>
 #include <optional>
 #include <string>
diff --git a/pc/simulcast_sdp_serializer_unittest.cc b/pc/simulcast_sdp_serializer_unittest.cc
index c92f08d..baf230c 100644
--- a/pc/simulcast_sdp_serializer_unittest.cc
+++ b/pc/simulcast_sdp_serializer_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "pc/simulcast_sdp_serializer.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <map>
 #include <string>
 #include <vector>
diff --git a/pc/slow_peer_connection_integration_test.cc b/pc/slow_peer_connection_integration_test.cc
index 8666edc..42d91ab 100644
--- a/pc/slow_peer_connection_integration_test.cc
+++ b/pc/slow_peer_connection_integration_test.cc
@@ -11,8 +11,7 @@
 // This file is intended for PeerConnection integration tests that are
 // slow to execute (currently defined as more than 5 seconds per test).
 
-#include <stdint.h>
-
+#include <cstdint>
 #include <memory>
 #include <string>
 #include <tuple>
diff --git a/pc/srtp_session.cc b/pc/srtp_session.cc
index 6d94c49..d1c533c 100644
--- a/pc/srtp_session.cc
+++ b/pc/srtp_session.cc
@@ -10,8 +10,6 @@
 
 #include "pc/srtp_session.h"
 
-#include <string.h>
-
 #include <cstdint>
 #include <cstring>
 #include <iomanip>
diff --git a/pc/srtp_session_unittest.cc b/pc/srtp_session_unittest.cc
index af00410..79a87ec 100644
--- a/pc/srtp_session_unittest.cc
+++ b/pc/srtp_session_unittest.cc
@@ -10,8 +10,6 @@
 
 #include "pc/srtp_session.h"
 
-#include <string.h>
-
 #include <cstdint>
 #include <cstring>
 #include <limits>
diff --git a/pc/srtp_transport_unittest.cc b/pc/srtp_transport_unittest.cc
index f0e8415..6de46be 100644
--- a/pc/srtp_transport_unittest.cc
+++ b/pc/srtp_transport_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "pc/srtp_transport.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <vector>
 
diff --git a/pc/test/fake_audio_capture_module.cc b/pc/test/fake_audio_capture_module.cc
index b9e42947..5283c32 100644
--- a/pc/test/fake_audio_capture_module.cc
+++ b/pc/test/fake_audio_capture_module.cc
@@ -10,9 +10,8 @@
 
 #include "pc/test/fake_audio_capture_module.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 
 #include "api/audio/audio_device_defines.h"
 #include "api/make_ref_counted.h"
diff --git a/pc/test/fake_audio_capture_module_unittest.cc b/pc/test/fake_audio_capture_module_unittest.cc
index b424916..ca0d104 100644
--- a/pc/test/fake_audio_capture_module_unittest.cc
+++ b/pc/test/fake_audio_capture_module_unittest.cc
@@ -10,10 +10,9 @@
 
 #include "pc/test/fake_audio_capture_module.h"
 
-#include <string.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 
 #include "api/audio/audio_device_defines.h"
 #include "api/scoped_refptr.h"
diff --git a/pc/test/peer_connection_test_wrapper.cc b/pc/test/peer_connection_test_wrapper.cc
index 8af879c..c70ce25 100644
--- a/pc/test/peer_connection_test_wrapper.cc
+++ b/pc/test/peer_connection_test_wrapper.cc
@@ -10,8 +10,7 @@
 
 #include "pc/test/peer_connection_test_wrapper.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/pc/track_media_info_map_unittest.cc b/pc/track_media_info_map_unittest.cc
index cd6bf36..e1c9822 100644
--- a/pc/track_media_info_map_unittest.cc
+++ b/pc/track_media_info_map_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "pc/track_media_info_map.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <initializer_list>
 #include <optional>
diff --git a/pc/typed_codec_vendor.cc b/pc/typed_codec_vendor.cc
index 486bd16..2f831d8 100644
--- a/pc/typed_codec_vendor.cc
+++ b/pc/typed_codec_vendor.cc
@@ -10,8 +10,7 @@
 
 #include "pc/typed_codec_vendor.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <functional>
 #include <map>
 #include <vector>
diff --git a/pc/video_rtp_receiver.cc b/pc/video_rtp_receiver.cc
index 0e18ade..402c27f 100644
--- a/pc/video_rtp_receiver.cc
+++ b/pc/video_rtp_receiver.cc
@@ -10,8 +10,7 @@
 
 #include "pc/video_rtp_receiver.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <optional>
 #include <string>
diff --git a/pc/video_rtp_track_source.cc b/pc/video_rtp_track_source.cc
index 7537de9..48fa27d 100644
--- a/pc/video_rtp_track_source.cc
+++ b/pc/video_rtp_track_source.cc
@@ -10,9 +10,8 @@
 
 #include "pc/video_rtp_track_source.h"
 
-#include <stddef.h>
-
 #include <algorithm>
+#include <cstddef>
 
 #include "api/sequence_checker.h"
 #include "api/video/recordable_encoded_frame.h"
diff --git a/pc/webrtc_sdp.cc b/pc/webrtc_sdp.cc
index 6e43467..be2de2b 100644
--- a/pc/webrtc_sdp.cc
+++ b/pc/webrtc_sdp.cc
@@ -10,10 +10,9 @@
 
 #include "pc/webrtc_sdp.h"
 
-#include <ctype.h>
-#include <limits.h>
-
 #include <algorithm>
+#include <cctype>
+#include <climits>
 #include <cstddef>
 #include <cstdint>
 #include <map>
diff --git a/pc/webrtc_sdp_unittest.cc b/pc/webrtc_sdp_unittest.cc
index 12c6a79..8ee712d 100644
--- a/pc/webrtc_sdp_unittest.cc
+++ b/pc/webrtc_sdp_unittest.cc
@@ -8,10 +8,9 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <stdio.h>
-#include <string.h>
-
 #include <cstdint>
+#include <cstdio>
+#include <cstring>
 #include <map>
 #include <memory>
 #include <optional>
diff --git a/pc/webrtc_session_description_factory.cc b/pc/webrtc_session_description_factory.cc
index 2c59f9e..248991b 100644
--- a/pc/webrtc_session_description_factory.cc
+++ b/pc/webrtc_session_description_factory.cc
@@ -10,8 +10,7 @@
 
 #include "pc/webrtc_session_description_factory.h"
 
-#include <stddef.h>
-
+#include <cstddef>
 #include <cstdint>
 #include <functional>
 #include <memory>
diff --git a/rtc_base/async_tcp_socket.cc b/rtc_base/async_tcp_socket.cc
index a13549c..b6046eb 100644
--- a/rtc_base/async_tcp_socket.cc
+++ b/rtc_base/async_tcp_socket.cc
@@ -10,12 +10,10 @@
 
 #include "rtc_base/async_tcp_socket.h"
 
-#include <stdint.h>
-#include <string.h>
-
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <utility>
 
@@ -29,10 +27,10 @@
 #include "rtc_base/network/sent_packet.h"
 #include "rtc_base/socket.h"
 #include "rtc_base/socket_address.h"
-#include "rtc_base/time_utils.h"  // for TimeMillis
+#include "rtc_base/time_utils.h"
 
 #if defined(WEBRTC_POSIX)
-#include <errno.h>
+#include <cerrno>
 #endif  // WEBRTC_POSIX
 
 namespace webrtc {
diff --git a/rtc_base/bitstream_reader.cc b/rtc_base/bitstream_reader.cc
index 3a53721..fb61bc7 100644
--- a/rtc_base/bitstream_reader.cc
+++ b/rtc_base/bitstream_reader.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/bitstream_reader.h"
 
-#include <stdint.h>
-
 #include <cstddef>
+#include <cstdint>
 #include <string>
 
 #include "absl/numeric/bits.h"
diff --git a/rtc_base/bitstream_reader_unittest.cc b/rtc_base/bitstream_reader_unittest.cc
index c85d054..4d76546 100644
--- a/rtc_base/bitstream_reader_unittest.cc
+++ b/rtc_base/bitstream_reader_unittest.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/bitstream_reader.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
 #include <array>
+#include <cstddef>
+#include <cstdint>
 #include <limits>
 #include <optional>
 #include <utility>
diff --git a/rtc_base/boringssl_identity.cc b/rtc_base/boringssl_identity.cc
index 4406962..c93abb1 100644
--- a/rtc_base/boringssl_identity.cc
+++ b/rtc_base/boringssl_identity.cc
@@ -14,9 +14,9 @@
 #include <openssl/err.h>
 #include <openssl/pem.h>
 #include <openssl/pool.h>
-#include <stdint.h>
-#include <string.h>
 
+#include <cstdint>
+#include <cstring>
 #include <ctime>
 #include <memory>
 #include <string>
diff --git a/rtc_base/buffer_queue.cc b/rtc_base/buffer_queue.cc
index c23365c..e791e91 100644
--- a/rtc_base/buffer_queue.cc
+++ b/rtc_base/buffer_queue.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/buffer_queue.h"
 
-#include <stdint.h>
-#include <string.h>
-
 #include <algorithm>
+#include <cstdint>
+#include <cstring>
 
 #include "api/sequence_checker.h"
 #include "rtc_base/buffer.h"
diff --git a/rtc_base/buffer_queue_unittest.cc b/rtc_base/buffer_queue_unittest.cc
index b0ebdd7..7348e5f 100644
--- a/rtc_base/buffer_queue_unittest.cc
+++ b/rtc_base/buffer_queue_unittest.cc
@@ -10,7 +10,7 @@
 
 #include "rtc_base/buffer_queue.h"
 
-#include <string.h>
+#include <cstring>
 
 #include "test/gtest.h"
 
diff --git a/rtc_base/byte_buffer.cc b/rtc_base/byte_buffer.cc
index 0cf153f..0b06d83 100644
--- a/rtc_base/byte_buffer.cc
+++ b/rtc_base/byte_buffer.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/byte_buffer.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <string>
 
 #include "absl/strings/string_view.h"
diff --git a/rtc_base/byte_buffer_unittest.cc b/rtc_base/byte_buffer_unittest.cc
index d0b93e2..07752b1 100644
--- a/rtc_base/byte_buffer_unittest.cc
+++ b/rtc_base/byte_buffer_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/byte_buffer.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <string>
 #include <utility>
 
diff --git a/rtc_base/byte_order_unittest.cc b/rtc_base/byte_order_unittest.cc
index da31631..8c1e10e 100644
--- a/rtc_base/byte_order_unittest.cc
+++ b/rtc_base/byte_order_unittest.cc
@@ -12,6 +12,8 @@
 
 #include <stdint.h>
 
+#include <cstdint>
+
 #include "test/gtest.h"
 
 namespace webrtc {
diff --git a/rtc_base/checks.cc b/rtc_base/checks.cc
index e5e9eb9..ca7cabf6 100644
--- a/rtc_base/checks.cc
+++ b/rtc_base/checks.cc
@@ -12,7 +12,6 @@
 // src/base/logging.cc.
 
 #include <stdlib.h>
-
 #include <cstdarg>
 #include <cstdio>
 #include <cstdlib>
@@ -34,7 +33,7 @@
 #elif defined(__native_client__) && __native_client__
 #define LAST_SYSTEM_ERROR (0)
 #elif defined(WEBRTC_POSIX)
-#include <errno.h>
+#include <cerrno>
 #define LAST_SYSTEM_ERROR (errno)
 #endif  // WEBRTC_WIN
 
diff --git a/rtc_base/copy_on_write_buffer.cc b/rtc_base/copy_on_write_buffer.cc
index ab53c95..3eaab59 100644
--- a/rtc_base/copy_on_write_buffer.cc
+++ b/rtc_base/copy_on_write_buffer.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/copy_on_write_buffer.h"
 
-#include <stddef.h>
-
 #include <algorithm>
+#include <cstddef>
 #include <cstring>
 #include <utility>
 
diff --git a/rtc_base/cpu_info.cc b/rtc_base/cpu_info.cc
index 56aba5e..22f7641 100644
--- a/rtc_base/cpu_info.cc
+++ b/rtc_base/cpu_info.cc
@@ -23,10 +23,11 @@
 #include <zircon/syscalls.h>
 #elif defined(WEBRTC_LINUX)
 #include <features.h>
-#include <stdlib.h>
-#include <string.h>  // IWYU pragma: keep
 #include <unistd.h>
 
+#include <cstdlib>
+#include <cstring>  // IWYU pragma: keep
+
 #ifdef __GLIBC_PREREQ
 #define WEBRTC_GLIBC_PREREQ(a, b) __GLIBC_PREREQ(a, b)
 #else
diff --git a/rtc_base/cpu_time.cc b/rtc_base/cpu_time.cc
index 0ae8906..2da8c5e 100644
--- a/rtc_base/cpu_time.cc
+++ b/rtc_base/cpu_time.cc
@@ -10,13 +10,15 @@
 
 #include "rtc_base/cpu_time.h"
 
+#include <time.h>
+
 #include <cstdint>
 
 #include "rtc_base/logging.h"
 #include "rtc_base/time_utils.h"
 
 #if defined(WEBRTC_LINUX)
-#include <time.h>
+#include <ctime>
 #elif defined(WEBRTC_MAC)
 #include <mach/mach_init.h>
 #include <mach/mach_port.h>
diff --git a/rtc_base/crypto_random_unittest.cc b/rtc_base/crypto_random_unittest.cc
index efc3617..7c5472d 100644
--- a/rtc_base/crypto_random_unittest.cc
+++ b/rtc_base/crypto_random_unittest.cc
@@ -10,8 +10,6 @@
 
 #include "rtc_base/crypto_random.h"
 
-#include <string.h>
-
 #include <cstdint>
 #include <cstring>
 #include <memory>
diff --git a/rtc_base/deprecated/recursive_critical_section_unittest.cc b/rtc_base/deprecated/recursive_critical_section_unittest.cc
index fedaaf5..0aac9bb 100644
--- a/rtc_base/deprecated/recursive_critical_section_unittest.cc
+++ b/rtc_base/deprecated/recursive_critical_section_unittest.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/deprecated/recursive_critical_section.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
 #include <atomic>
+#include <cstddef>
+#include <cstdint>
 #include <memory>
 #include <set>
 #include <utility>
diff --git a/rtc_base/event.cc b/rtc_base/event.cc
index abd9619..05f477c 100644
--- a/rtc_base/event.cc
+++ b/rtc_base/event.cc
@@ -10,6 +10,8 @@
 
 #include "rtc_base/event.h"
 
+#include <time.h>
+
 #include <cstdint>
 #include <optional>
 
@@ -22,12 +24,13 @@
 #if defined(WEBRTC_WIN)
 #include <windows.h>
 #elif defined(WEBRTC_POSIX)
-#include <errno.h>
 #include <pthread.h>
+
+#include <cerrno>
 #ifdef WEBRTC_MAC
 #include <sys/time.h>
 #endif
-#include <time.h>
+#include <ctime>
 #else
 #error "Must define either WEBRTC_WIN or WEBRTC_POSIX."
 #endif
diff --git a/rtc_base/event_tracer.cc b/rtc_base/event_tracer.cc
index b42757c..82ed2c4 100644
--- a/rtc_base/event_tracer.cc
+++ b/rtc_base/event_tracer.cc
@@ -10,7 +10,7 @@
 
 #include "rtc_base/event_tracer.h"
 
-#include <stdio.h>
+#include <cstdio>
 
 #include "api/units/time_delta.h"
 #include "rtc_base/trace_event.h"
@@ -19,11 +19,10 @@
 #include "rtc_base/trace_categories.h"
 #include "third_party/perfetto/include/perfetto/tracing/tracing.h"
 #else
-#include <inttypes.h>
-#include <stdint.h>
-#include <string.h>
-
 #include <atomic>
+#include <cinttypes>
+#include <cstdint>
+#include <cstring>
 #include <string>
 #include <vector>
 
diff --git a/rtc_base/experiments/alr_experiment.cc b/rtc_base/experiments/alr_experiment.cc
index 2138e34..a0fe9d9 100644
--- a/rtc_base/experiments/alr_experiment.cc
+++ b/rtc_base/experiments/alr_experiment.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/experiments/alr_experiment.h"
 
-#include <inttypes.h>
-#include <stdio.h>
-
+#include <cinttypes>
+#include <cstdio>
 #include <optional>
 #include <string>
 
diff --git a/rtc_base/experiments/encoder_info_settings.cc b/rtc_base/experiments/encoder_info_settings.cc
index bfc5502..4acfeac 100644
--- a/rtc_base/experiments/encoder_info_settings.cc
+++ b/rtc_base/experiments/encoder_info_settings.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/experiments/encoder_info_settings.h"
 
-#include <stdio.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstdio>
 #include <optional>
 #include <string>
 #include <vector>
diff --git a/rtc_base/experiments/field_trial_parser.cc b/rtc_base/experiments/field_trial_parser.cc
index ada8f5c..88e2b1a 100644
--- a/rtc_base/experiments/field_trial_parser.cc
+++ b/rtc_base/experiments/field_trial_parser.cc
@@ -9,8 +9,7 @@
  */
 #include "rtc_base/experiments/field_trial_parser.h"
 
-#include <inttypes.h>
-
+#include <cinttypes>
 #include <cstddef>
 #include <cstdint>
 #include <cstdio>
diff --git a/rtc_base/experiments/field_trial_units.cc b/rtc_base/experiments/field_trial_units.cc
index e7a5b11..f65db33 100644
--- a/rtc_base/experiments/field_trial_units.cc
+++ b/rtc_base/experiments/field_trial_units.cc
@@ -9,8 +9,7 @@
  */
 #include "rtc_base/experiments/field_trial_units.h"
 
-#include <stdio.h>
-
+#include <cstdio>
 #include <limits>
 #include <optional>
 #include <string>
diff --git a/rtc_base/experiments/normalize_simulcast_size_experiment.cc b/rtc_base/experiments/normalize_simulcast_size_experiment.cc
index 3e949c5..81c1752 100644
--- a/rtc_base/experiments/normalize_simulcast_size_experiment.cc
+++ b/rtc_base/experiments/normalize_simulcast_size_experiment.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/experiments/normalize_simulcast_size_experiment.h"
 
-#include <stdio.h>
-
+#include <cstdio>
 #include <optional>
 #include <string>
 
diff --git a/rtc_base/experiments/quality_scaling_experiment.cc b/rtc_base/experiments/quality_scaling_experiment.cc
index ff87e19..82b7f27 100644
--- a/rtc_base/experiments/quality_scaling_experiment.cc
+++ b/rtc_base/experiments/quality_scaling_experiment.cc
@@ -9,8 +9,7 @@
  */
 #include "rtc_base/experiments/quality_scaling_experiment.h"
 
-#include <stdio.h>
-
+#include <cstdio>
 #include <optional>
 #include <string>
 
diff --git a/rtc_base/experiments/rate_control_settings.cc b/rtc_base/experiments/rate_control_settings.cc
index 2d37c2d..06c5e6f 100644
--- a/rtc_base/experiments/rate_control_settings.cc
+++ b/rtc_base/experiments/rate_control_settings.cc
@@ -10,8 +10,6 @@
 
 #include "rtc_base/experiments/rate_control_settings.h"
 
-#include <stdio.h>
-
 #include <cstdint>
 #include <memory>
 #include <optional>
diff --git a/rtc_base/file_rotating_stream_unittest.cc b/rtc_base/file_rotating_stream_unittest.cc
index 50a0fe9..1270cdd 100644
--- a/rtc_base/file_rotating_stream_unittest.cc
+++ b/rtc_base/file_rotating_stream_unittest.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/file_rotating_stream.h"
 
-#include <string.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <string>
 
diff --git a/rtc_base/firewall_socket_server.cc b/rtc_base/firewall_socket_server.cc
index ab8c331..aaf68f4 100644
--- a/rtc_base/firewall_socket_server.cc
+++ b/rtc_base/firewall_socket_server.cc
@@ -10,11 +10,10 @@
 
 #include "rtc_base/firewall_socket_server.h"
 
-#include <errno.h>
-#include <stddef.h>
-#include <stdint.h>
-
 #include <algorithm>
+#include <cerrno>
+#include <cstddef>
+#include <cstdint>
 #include <vector>
 
 #include "absl/algorithm/container.h"
diff --git a/rtc_base/log_sinks.cc b/rtc_base/log_sinks.cc
index 7f5b383..0db3475 100644
--- a/rtc_base/log_sinks.cc
+++ b/rtc_base/log_sinks.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/log_sinks.h"
 
-#include <string.h>
-
 #include <cstdio>
+#include <cstring>
 #include <string>
 
 #include "absl/strings/string_view.h"
diff --git a/rtc_base/logging.cc b/rtc_base/logging.cc
index 1a07e96..eee7f21 100644
--- a/rtc_base/logging.cc
+++ b/rtc_base/logging.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/logging.h"
 
-#include <string.h>
-
 #include <atomic>
 #include <cstdint>
+#include <cstring>
 #include <string>
 
 #if RTC_LOG_ENABLED()
@@ -37,12 +36,11 @@
 static const int kMaxLogLineSize = 1024 - 60;
 #endif  // WEBRTC_MAC && !defined(WEBRTC_IOS) || WEBRTC_ANDROID
 
-#include <inttypes.h>
-#include <stdio.h>
-#include <time.h>
-
 #include <algorithm>
+#include <cinttypes>
 #include <cstdarg>
+#include <cstdio>
+#include <ctime>
 #include <vector>
 
 #include "absl/base/attributes.h"
diff --git a/rtc_base/memory/aligned_malloc.cc b/rtc_base/memory/aligned_malloc.cc
index e0bae74..36aa749 100644
--- a/rtc_base/memory/aligned_malloc.cc
+++ b/rtc_base/memory/aligned_malloc.cc
@@ -10,15 +10,15 @@
 
 #include "rtc_base/memory/aligned_malloc.h"
 
-#include <stdlib.h>  // for free, malloc
-#include <string.h>  // for memcpy
+#include <cstdlib>
+#include <cstring>
 
 #include "rtc_base/checks.h"
 
 #ifdef _WIN32
 #include <windows.h>
 #else
-#include <stdint.h>
+#include <cstdint>
 #endif
 
 // Reference on memory alignment:
diff --git a/rtc_base/memory/aligned_malloc_unittest.cc b/rtc_base/memory/aligned_malloc_unittest.cc
index 56ec95d..a2d5c6e 100644
--- a/rtc_base/memory/aligned_malloc_unittest.cc
+++ b/rtc_base/memory/aligned_malloc_unittest.cc
@@ -16,7 +16,7 @@
 #ifdef _WIN32
 #include <windows.h>
 #else
-#include <stdint.h>
+#include <cstdint>
 #endif
 
 #include "test/gtest.h"
diff --git a/rtc_base/memory/fifo_buffer_unittest.cc b/rtc_base/memory/fifo_buffer_unittest.cc
index c78cf90..22f78a4 100644
--- a/rtc_base/memory/fifo_buffer_unittest.cc
+++ b/rtc_base/memory/fifo_buffer_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/memory/fifo_buffer.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 
 #include "api/array_view.h"
 #include "rtc_base/stream.h"
diff --git a/rtc_base/memory_stream.cc b/rtc_base/memory_stream.cc
index d0b6acb..9134d61 100644
--- a/rtc_base/memory_stream.cc
+++ b/rtc_base/memory_stream.cc
@@ -10,11 +10,10 @@
 
 #include "rtc_base/memory_stream.h"
 
-#include <errno.h>
-#include <string.h>
-
 #include <algorithm>
+#include <cerrno>
 #include <cstdint>
+#include <cstring>
 
 #include "api/array_view.h"
 #include "rtc_base/checks.h"
diff --git a/rtc_base/message_digest.cc b/rtc_base/message_digest.cc
index d25ab40..d63187d 100644
--- a/rtc_base/message_digest.cc
+++ b/rtc_base/message_digest.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/message_digest.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <string>
 
diff --git a/rtc_base/network_unittest.cc b/rtc_base/network_unittest.cc
index dde29cb..3b7edc22f 100644
--- a/rtc_base/network_unittest.cc
+++ b/rtc_base/network_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/network.h"
 
-#include <stdlib.h>
-
 #include <cstdint>
+#include <cstdlib>
 #include <cstring>
 #include <memory>
 #include <string>
diff --git a/rtc_base/null_socket_server_unittest.cc b/rtc_base/null_socket_server_unittest.cc
index 81da9c3..3b47acc 100644
--- a/rtc_base/null_socket_server_unittest.cc
+++ b/rtc_base/null_socket_server_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/null_socket_server.h"
 
-#include <stdint.h>
-
+#include <cstdint>
 #include <memory>
 
 #include "api/test/rtc_error_matchers.h"
diff --git a/rtc_base/numerics/mod_ops_unittest.cc b/rtc_base/numerics/mod_ops_unittest.cc
index 3bd2034..839e9b0 100644
--- a/rtc_base/numerics/mod_ops_unittest.cc
+++ b/rtc_base/numerics/mod_ops_unittest.cc
@@ -10,7 +10,7 @@
 
 #include "rtc_base/numerics/mod_ops.h"
 
-#include <stdint.h>
+#include <cstdint>
 
 #include "test/gtest.h"
 
diff --git a/rtc_base/numerics/moving_percentile_filter_unittest.cc b/rtc_base/numerics/moving_percentile_filter_unittest.cc
index f456108..bcf9bd9 100644
--- a/rtc_base/numerics/moving_percentile_filter_unittest.cc
+++ b/rtc_base/numerics/moving_percentile_filter_unittest.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/numerics/moving_percentile_filter.h"
 
-#include <stdint.h>
-
 #include <algorithm>
 #include <cstddef>
+#include <cstdint>
 
 #include "test/gtest.h"
 
diff --git a/rtc_base/numerics/percentile_filter_unittest.cc b/rtc_base/numerics/percentile_filter_unittest.cc
index d6826f4..ce4183d 100644
--- a/rtc_base/numerics/percentile_filter_unittest.cc
+++ b/rtc_base/numerics/percentile_filter_unittest.cc
@@ -10,11 +10,10 @@
 
 #include "rtc_base/numerics/percentile_filter.h"
 
-#include <stdlib.h>
-
 #include <array>
 #include <climits>
 #include <cstdint>
+#include <cstdlib>
 #include <numbers>
 #include <random>
 
diff --git a/rtc_base/numerics/running_statistics_unittest.cc b/rtc_base/numerics/running_statistics_unittest.cc
index 7f8adfb..f946bc3 100644
--- a/rtc_base/numerics/running_statistics_unittest.cc
+++ b/rtc_base/numerics/running_statistics_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/numerics/running_statistics.h"
 
-#include <math.h>
-
+#include <cmath>
 #include <random>
 #include <vector>
 
diff --git a/rtc_base/openssl_adapter.cc b/rtc_base/openssl_adapter.cc
index 4a74944b..6ac2c66 100644
--- a/rtc_base/openssl_adapter.cc
+++ b/rtc_base/openssl_adapter.cc
@@ -10,13 +10,13 @@
 
 #include "rtc_base/openssl_adapter.h"
 
-#include <errno.h>
 #include <openssl/bio.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 #include <openssl/ssl3.h>
 #include <openssl/x509.h>
 
+#include <cerrno>
 #include <cstdint>
 #include <cstring>
 #include <ctime>
diff --git a/rtc_base/openssl_session_cache_unittest.cc b/rtc_base/openssl_session_cache_unittest.cc
index 1d4f181..4b4da722 100644
--- a/rtc_base/openssl_session_cache_unittest.cc
+++ b/rtc_base/openssl_session_cache_unittest.cc
@@ -11,7 +11,8 @@
 #include "rtc_base/openssl_session_cache.h"
 
 #include <openssl/ssl.h>
-#include <stdlib.h>
+
+#include <cstdlib>
 
 #include "rtc_base/ssl_stream_adapter.h"
 #include "test/gtest.h"
diff --git a/rtc_base/proxy_server.cc b/rtc_base/proxy_server.cc
index d9b94c5..8ef45cf 100644
--- a/rtc_base/proxy_server.cc
+++ b/rtc_base/proxy_server.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/proxy_server.h"
 
-#include <stddef.h>
-
 #include <algorithm>
+#include <cstddef>
 #include <memory>
 
 #include "rtc_base/checks.h"
diff --git a/rtc_base/random.cc b/rtc_base/random.cc
index 319ad72..8fd23ea 100644
--- a/rtc_base/random.cc
+++ b/rtc_base/random.cc
@@ -9,8 +9,7 @@
  */
 #include "rtc_base/random.h"
 
-#include <math.h>
-
+#include <cmath>
 #include <cstdint>
 #include <numbers>
 
diff --git a/rtc_base/random_unittest.cc b/rtc_base/random_unittest.cc
index d1827cd..3c3d276 100644
--- a/rtc_base/random_unittest.cc
+++ b/rtc_base/random_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/random.h"
 
-#include <math.h>
-
+#include <cmath>
 #include <cstdint>
 #include <limits>
 #include <numbers>
diff --git a/rtc_base/rtc_certificate_generator.cc b/rtc_base/rtc_certificate_generator.cc
index d496e2f..bbcec2c 100644
--- a/rtc_base/rtc_certificate_generator.cc
+++ b/rtc_base/rtc_certificate_generator.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/rtc_certificate_generator.h"
 
-#include <time.h>
-
 #include <algorithm>
 #include <cstdint>
+#include <ctime>
 #include <memory>
 #include <optional>
 #include <utility>
diff --git a/rtc_base/rtc_certificate_unittest.cc b/rtc_base/rtc_certificate_unittest.cc
index 9e578bc..9f95bff 100644
--- a/rtc_base/rtc_certificate_unittest.cc
+++ b/rtc_base/rtc_certificate_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/rtc_certificate.h"
 
-#include <time.h>
-
 #include <cstdint>
+#include <ctime>
 #include <memory>
 #include <utility>
 
diff --git a/rtc_base/sanitizer_unittest.cc b/rtc_base/sanitizer_unittest.cc
index e293a43..d77a5c6 100644
--- a/rtc_base/sanitizer_unittest.cc
+++ b/rtc_base/sanitizer_unittest.cc
@@ -10,7 +10,7 @@
 
 #include "rtc_base/sanitizer.h"
 
-#include <stdint.h>
+#include <cstdint>
 
 #include "rtc_base/logging.h"
 #include "test/gtest.h"
diff --git a/rtc_base/socket_address_unittest.cc b/rtc_base/socket_address_unittest.cc
index e81fb6d..fa9bf82 100644
--- a/rtc_base/socket_address_unittest.cc
+++ b/rtc_base/socket_address_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/socket_address.h"
 
-#include <string.h>
-
+#include <cstring>
 #include <string>
 
 #include "rtc_base/ip_address.h"
diff --git a/rtc_base/socket_unittest.cc b/rtc_base/socket_unittest.cc
index bd3c860..90dd4855 100644
--- a/rtc_base/socket_unittest.cc
+++ b/rtc_base/socket_unittest.cc
@@ -10,12 +10,10 @@
 
 #include "rtc_base/socket.h"
 
-#include <errno.h>
-#include <stdint.h>
-#include <string.h>
-
+#include <cerrno>
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <string>
 #include <utility>
diff --git a/rtc_base/ssl_fingerprint.cc b/rtc_base/ssl_fingerprint.cc
index ca15d11..f3f6fa6 100644
--- a/rtc_base/ssl_fingerprint.cc
+++ b/rtc_base/ssl_fingerprint.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/ssl_fingerprint.h"
 
-#include <ctype.h>
-
+#include <cctype>
 #include <cstddef>
 #include <cstdint>
 #include <memory>
diff --git a/rtc_base/ssl_identity.cc b/rtc_base/ssl_identity.cc
index 35930f8..2186d3a 100644
--- a/rtc_base/ssl_identity.cc
+++ b/rtc_base/ssl_identity.cc
@@ -12,10 +12,10 @@
 #include "rtc_base/ssl_identity.h"
 
 #include <openssl/ossl_typ.h>
-#include <string.h>
-#include <time.h>
 
 #include <cstdint>
+#include <cstring>
+#include <ctime>
 #include <memory>
 #include <optional>
 #include <string>
diff --git a/rtc_base/ssl_identity_unittest.cc b/rtc_base/ssl_identity_unittest.cc
index 0dc4e2b..fb6ff08 100644
--- a/rtc_base/ssl_identity_unittest.cc
+++ b/rtc_base/ssl_identity_unittest.cc
@@ -16,7 +16,6 @@
 #include <openssl/evp.h>  // IWYU pragma: keep
 #endif
 #include <openssl/sha.h>
-#include <string.h>
 
 #include <array>
 #include <cstdint>
diff --git a/rtc_base/stream.cc b/rtc_base/stream.cc
index 696f1ad..9731781 100644
--- a/rtc_base/stream.cc
+++ b/rtc_base/stream.cc
@@ -9,9 +9,8 @@
  */
 #include "rtc_base/stream.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 
 #include "api/array_view.h"
 
diff --git a/rtc_base/string_encode_unittest.cc b/rtc_base/string_encode_unittest.cc
index 103d33c..d26cd6b 100644
--- a/rtc_base/string_encode_unittest.cc
+++ b/rtc_base/string_encode_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/string_encode.h"
 
-#include <string.h>
-
+#include <cstring>
 #include <string>
 #include <vector>
 
diff --git a/rtc_base/string_to_number.cc b/rtc_base/string_to_number.cc
index 837a6bb..443b8c5 100644
--- a/rtc_base/string_to_number.cc
+++ b/rtc_base/string_to_number.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/string_to_number.h"
 
-#include <ctype.h>
-
+#include <cctype>
 #include <cerrno>
 #include <cstdlib>
 #include <optional>
diff --git a/rtc_base/string_to_number_unittest.cc b/rtc_base/string_to_number_unittest.cc
index 77b1437..3aa6afc 100644
--- a/rtc_base/string_to_number_unittest.cc
+++ b/rtc_base/string_to_number_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/string_to_number.h"
 
-#include <stdint.h>
-
+#include <cstdint>
 #include <limits>
 #include <optional>
 #include <string>
diff --git a/rtc_base/strings/json.cc b/rtc_base/strings/json.cc
index c488304..a7e071e 100644
--- a/rtc_base/strings/json.cc
+++ b/rtc_base/strings/json.cc
@@ -10,10 +10,9 @@
 
 #include "rtc_base/strings/json.h"
 
-#include <errno.h>
-#include <limits.h>
-#include <stdlib.h>
-
+#include <cerrno>
+#include <climits>
+#include <cstdlib>
 #include <string>
 #include <vector>
 
diff --git a/rtc_base/strings/string_builder.cc b/rtc_base/strings/string_builder.cc
index e411150..094bbd1 100644
--- a/rtc_base/strings/string_builder.cc
+++ b/rtc_base/strings/string_builder.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/strings/string_builder.h"
 
-#include <stdarg.h>
-
+#include <cstdarg>
 #include <cstdio>
 #include <cstring>
 
diff --git a/rtc_base/strings/string_builder_unittest.cc b/rtc_base/strings/string_builder_unittest.cc
index 18d5020..4d7629e 100644
--- a/rtc_base/strings/string_builder_unittest.cc
+++ b/rtc_base/strings/string_builder_unittest.cc
@@ -10,8 +10,7 @@
 
 #include "rtc_base/strings/string_builder.h"
 
-#include <string.h>
-
+#include <cstring>
 #include <string>
 
 #include "rtc_base/checks.h"
diff --git a/rtc_base/synchronization/yield.cc b/rtc_base/synchronization/yield.cc
index 3b1bc3d..812dfe6 100644
--- a/rtc_base/synchronization/yield.cc
+++ b/rtc_base/synchronization/yield.cc
@@ -10,10 +10,12 @@
 
 #include "rtc_base/synchronization/yield.h"
 
+#include <time.h>
+
 #if defined(WEBRTC_WIN)
 #include <windows.h>
 #else
-#include <time.h>
+#include <ctime>
 #endif
 
 namespace webrtc {
diff --git a/rtc_base/system/file_wrapper_unittest.cc b/rtc_base/system/file_wrapper_unittest.cc
index ef59656..d1ba182 100644
--- a/rtc_base/system/file_wrapper_unittest.cc
+++ b/rtc_base/system/file_wrapper_unittest.cc
@@ -14,6 +14,7 @@
 
 #include <algorithm>
 #include <cstddef>
+#include <cstdio>
 #include <cstring>
 #include <string>
 
diff --git a/rtc_base/test_client.cc b/rtc_base/test_client.cc
index a204d1c..a7577d5 100644
--- a/rtc_base/test_client.cc
+++ b/rtc_base/test_client.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/test_client.h"
 
-#include <string.h>
-
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <optional>
 #include <utility>
diff --git a/rtc_base/thread.cc b/rtc_base/thread.cc
index 815ac34..04fa8f2 100644
--- a/rtc_base/thread.cc
+++ b/rtc_base/thread.cc
@@ -10,6 +10,8 @@
 
 #include "rtc_base/thread.h"
 
+#include <time.h>
+
 #include <algorithm>
 #include <atomic>
 #include <cstdint>
@@ -32,7 +34,8 @@
 #include <comdef.h>
 #elif defined(WEBRTC_POSIX)
 #include <pthread.h>
-#include <time.h>
+
+#include <ctime>
 #else
 #error "Either WEBRTC_WIN or WEBRTC_POSIX needs to be defined."
 #endif
@@ -43,8 +46,7 @@
 #pragma warning(disable : 4722)
 #endif
 
-#include <stdio.h>
-
+#include <cstdio>
 #include <utility>
 
 #include "absl/algorithm/container.h"
diff --git a/rtc_base/timestamp_aligner_unittest.cc b/rtc_base/timestamp_aligner_unittest.cc
index 2582c78..d8df07a 100644
--- a/rtc_base/timestamp_aligner_unittest.cc
+++ b/rtc_base/timestamp_aligner_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/timestamp_aligner.h"
 
-#include <math.h>
-
 #include <algorithm>
+#include <cmath>
 #include <cstdint>
 #include <limits>
 
diff --git a/rtc_base/virtual_socket_unittest.cc b/rtc_base/virtual_socket_unittest.cc
index 22988a5..5d6a1e0 100644
--- a/rtc_base/virtual_socket_unittest.cc
+++ b/rtc_base/virtual_socket_unittest.cc
@@ -8,13 +8,12 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <math.h>
-#include <stdint.h>
-#include <stdlib.h>
-#include <string.h>
-#include <time.h>
-
 #include <algorithm>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
 #include <memory>
 
 #include "absl/memory/memory.h"
diff --git a/rtc_base/zero_memory.cc b/rtc_base/zero_memory.cc
index 2727ed9..66e6b1c 100644
--- a/rtc_base/zero_memory.cc
+++ b/rtc_base/zero_memory.cc
@@ -11,7 +11,7 @@
 #if defined(WEBRTC_WIN)
 #include <windows.h>
 #else
-#include <string.h>
+#include <cstring>
 #endif
 
 #include "rtc_base/checks.h"
diff --git a/rtc_base/zero_memory_unittest.cc b/rtc_base/zero_memory_unittest.cc
index f333266..5a8804c 100644
--- a/rtc_base/zero_memory_unittest.cc
+++ b/rtc_base/zero_memory_unittest.cc
@@ -10,9 +10,8 @@
 
 #include "rtc_base/zero_memory.h"
 
-#include <stdint.h>
-
 #include <cstddef>
+#include <cstdint>
 
 #include "api/array_view.h"
 #include "test/gtest.h"