diff --git a/logging/rtc_event_log/events/logged_rtp_rtcp.h b/logging/rtc_event_log/events/logged_rtp_rtcp.h
index b0f2ec3..f52664e 100644
--- a/logging/rtc_event_log/events/logged_rtp_rtcp.h
+++ b/logging/rtc_event_log/events/logged_rtp_rtcp.h
@@ -20,6 +20,7 @@
 #include "api/rtp_headers.h"
 #include "api/units/timestamp.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/bye.h"
+#include "modules/rtp_rtcp/source/rtcp_packet/congestion_control_feedback.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/extended_reports.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/fir.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/loss_notification.h"
@@ -232,6 +233,20 @@
   rtcp::TransportFeedback transport_feedback;
 };
 
+struct LoggedRtcpCongestionControlFeedback {
+  LoggedRtcpCongestionControlFeedback(
+      Timestamp timestamp,
+      const rtcp::CongestionControlFeedback& congestion_feedback)
+      : timestamp(timestamp), congestion_feedback(congestion_feedback) {}
+
+  int64_t log_time_us() const { return timestamp.us(); }
+  int64_t log_time_ms() const { return timestamp.ms(); }
+  Timestamp log_time() const { return timestamp; }
+
+  Timestamp timestamp;
+  rtcp::CongestionControlFeedback congestion_feedback;
+};
+
 struct LoggedRtcpPacketLossNotification {
   LoggedRtcpPacketLossNotification() = default;
   LoggedRtcpPacketLossNotification(
diff --git a/logging/rtc_event_log/rtc_event_log_parser.cc b/logging/rtc_event_log/rtc_event_log_parser.cc
index 241853b..1daf661 100644
--- a/logging/rtc_event_log/rtc_event_log_parser.cc
+++ b/logging/rtc_event_log/rtc_event_log_parser.cc
@@ -80,6 +80,7 @@
 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/bye.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
+#include "modules/rtp_rtcp/source/rtcp_packet/congestion_control_feedback.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/extended_reports.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/fir.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/nack.h"
@@ -753,6 +754,7 @@
     std::vector<LoggedRtcpPacketPli>* pli_list,
     std::vector<LoggedRtcpPacketBye>* bye_list,
     std::vector<LoggedRtcpPacketTransportFeedback>* transport_feedback_list,
+    std::vector<LoggedRtcpCongestionControlFeedback>* congestion_feedback_list,
     std::vector<LoggedRtcpPacketLossNotification>* loss_notification_list) {
   Timestamp timestamp = Timestamp::Micros(timestamp_us);
   rtcp::CommonHeader header;
@@ -765,6 +767,12 @@
       parsed_block.timestamp = timestamp;
       RTC_PARSE_CHECK_OR_RETURN(parsed_block.transport_feedback.Parse(header));
       transport_feedback_list->push_back(std::move(parsed_block));
+    } else if (header.type() == rtcp::Rtpfb::kPacketType &&
+               header.fmt() ==
+                   rtcp::CongestionControlFeedback::kFeedbackMessageType) {
+      rtcp::CongestionControlFeedback feedback;
+      RTC_PARSE_CHECK_OR_RETURN(feedback.Parse(header));
+      congestion_feedback_list->emplace_back(timestamp, std::move(feedback));
     } else if (header.type() == rtcp::SenderReport::kPacketType) {
       LoggedRtcpPacketSenderReport parsed_block;
       parsed_block.timestamp = timestamp;
@@ -1309,7 +1317,7 @@
         timestamp_us, packet_begin, packet_end, &incoming_sr_, &incoming_rr_,
         &incoming_xr_, &incoming_remb_, &incoming_nack_, &incoming_fir_,
         &incoming_pli_, &incoming_bye_, &incoming_transport_feedback_,
-        &incoming_loss_notification_);
+        &incoming_congestion_feedback_, &incoming_loss_notification_);
     RTC_RETURN_IF_ERROR(store_rtcp_status);
   }
 
@@ -1321,7 +1329,7 @@
         timestamp_us, packet_begin, packet_end, &outgoing_sr_, &outgoing_rr_,
         &outgoing_xr_, &outgoing_remb_, &outgoing_nack_, &outgoing_fir_,
         &outgoing_pli_, &outgoing_bye_, &outgoing_transport_feedback_,
-        &outgoing_loss_notification_);
+        &outgoing_congestion_feedback_, &outgoing_loss_notification_);
     RTC_RETURN_IF_ERROR(store_rtcp_status);
   }
 
diff --git a/logging/rtc_event_log/rtc_event_log_parser.h b/logging/rtc_event_log/rtc_event_log_parser.h
index 1dd65e7..4fdeba6 100644
--- a/logging/rtc_event_log/rtc_event_log_parser.h
+++ b/logging/rtc_event_log/rtc_event_log_parser.h
@@ -632,6 +632,15 @@
     }
   }
 
+  const std::vector<LoggedRtcpCongestionControlFeedback>& congestion_feedback(
+      PacketDirection direction) const {
+    if (direction == kIncomingPacket) {
+      return incoming_congestion_feedback_;
+    } else {
+      return outgoing_congestion_feedback_;
+    }
+  }
+
   const std::vector<LoggedRtcpPacketLossNotification>& loss_notifications(
       PacketDirection direction) {
     if (direction == kIncomingPacket) {
@@ -865,6 +874,10 @@
   std::vector<LoggedRtcpPacketBye> outgoing_bye_;
   std::vector<LoggedRtcpPacketTransportFeedback> incoming_transport_feedback_;
   std::vector<LoggedRtcpPacketTransportFeedback> outgoing_transport_feedback_;
+  std::vector<LoggedRtcpCongestionControlFeedback>
+      incoming_congestion_feedback_;
+  std::vector<LoggedRtcpCongestionControlFeedback>
+      outgoing_congestion_feedback_;
   std::vector<LoggedRtcpPacketLossNotification> incoming_loss_notification_;
   std::vector<LoggedRtcpPacketLossNotification> outgoing_loss_notification_;
 
diff --git a/rtc_tools/BUILD.gn b/rtc_tools/BUILD.gn
index a5fa6c8..68521ba 100644
--- a/rtc_tools/BUILD.gn
+++ b/rtc_tools/BUILD.gn
@@ -365,6 +365,7 @@
         "../api/neteq:neteq_api",
         "../api/rtc_event_log:rtc_event_log",
         "../api/transport:bandwidth_usage",
+        "../api/transport:ecn_marking",
         "../api/transport:field_trial_based_config",
         "../api/transport:goog_cc",
         "../api/transport:network_control",
diff --git a/rtc_tools/rtc_event_log_visualizer/analyzer.cc b/rtc_tools/rtc_event_log_visualizer/analyzer.cc
index cc51c79..f6acc90 100644
--- a/rtc_tools/rtc_event_log_visualizer/analyzer.cc
+++ b/rtc_tools/rtc_event_log_visualizer/analyzer.cc
@@ -36,6 +36,7 @@
 #include "api/rtc_event_log/rtc_event_log.h"
 #include "api/rtp_headers.h"
 #include "api/transport/bandwidth_usage.h"
+#include "api/transport/ecn_marking.h"
 #include "api/transport/goog_cc_factory.h"
 #include "api/transport/network_control.h"
 #include "api/transport/network_types.h"
@@ -55,6 +56,7 @@
 #include "modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h"
 #include "modules/rtp_rtcp/include/rtp_header_extension_map.h"
 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
+#include "modules/rtp_rtcp/source/rtcp_packet/congestion_control_feedback.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/receiver_report.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/remb.h"
 #include "modules/rtp_rtcp/source/rtcp_packet/report_block.h"
@@ -617,6 +619,12 @@
   plots_.RegisterPlot("outgoing_twcc_loss", [this](Plot* plot) {
     this->CreateOutgoingTWCCLossRateGraph(plot);
   });
+  plots_.RegisterPlot("outgoing_ecn_feedback", [this](Plot* plot) {
+    this->CreateOutgoingEcnFeedbackGraph(plot);
+  });
+  plots_.RegisterPlot("incoming_ecn_feedback", [this](Plot* plot) {
+    this->CreateIncomingEcnFeedbackGraph(plot);
+  });
   plots_.RegisterPlot("network_delay_feedback", [this](Plot* plot) {
     this->CreateNetworkDelayFeedbackGraph(plot);
   });
@@ -1557,6 +1565,65 @@
   plot->SetTitle("Simulated BWE behavior");
 }
 
+void EventLogAnalyzer::CreateOutgoingEcnFeedbackGraph(Plot* plot) const {
+  CreateEcnFeedbackGraph(plot, kOutgoingPacket);
+  plot->SetTitle("Outgoing ECN count per feedback");
+}
+
+void EventLogAnalyzer::CreateIncomingEcnFeedbackGraph(Plot* plot) const {
+  CreateEcnFeedbackGraph(plot, kIncomingPacket);
+  plot->SetTitle("Incoming ECN count per feedback");
+}
+
+void EventLogAnalyzer::CreateEcnFeedbackGraph(Plot* plot,
+                                              PacketDirection direction) const {
+  TimeSeries not_ect("Not ECN capable", LineStyle::kBar,
+                     PointStyle::kHighlight);
+  TimeSeries ect_1("ECN capable", LineStyle::kBar, PointStyle::kHighlight);
+  TimeSeries ce("Congestion experienced", LineStyle::kBar,
+                PointStyle::kHighlight);
+
+  for (const LoggedRtcpCongestionControlFeedback& feedback :
+       parsed_log_.congestion_feedback(direction)) {
+    int ect_1_count = 0;
+    int not_ect_count = 0;
+    int ce_count = 0;
+
+    for (const rtcp::CongestionControlFeedback::PacketInfo& info :
+         feedback.congestion_feedback.packets()) {
+      switch (info.ecn) {
+        case webrtc::EcnMarking::kNotEct:
+          ++not_ect_count;
+          break;
+        case webrtc::EcnMarking::kEct1:
+          ++ect_1_count;
+          break;
+        case webrtc::EcnMarking::kEct0:
+          RTC_LOG(LS_ERROR) << "unexpected ect(0)";
+          break;
+        case webrtc::EcnMarking::kCe:
+          ++ce_count;
+          break;
+      }
+    }
+    ect_1.points.emplace_back(config_.GetCallTimeSec(feedback.timestamp),
+                              ect_1_count);
+    not_ect.points.emplace_back(config_.GetCallTimeSec(feedback.timestamp),
+                                not_ect_count);
+    ce.points.emplace_back(config_.GetCallTimeSec(feedback.timestamp),
+                           ce_count);
+  }
+
+  plot->AppendTimeSeriesIfNotEmpty(std::move(ect_1));
+  plot->AppendTimeSeriesIfNotEmpty(std::move(not_ect));
+  plot->AppendTimeSeriesIfNotEmpty(std::move(ce));
+
+  plot->SetXAxis(config_.CallBeginTimeSec(), config_.CallEndTimeSec(),
+                 "Time (s)", kLeftMargin, kRightMargin);
+  plot->SetSuggestedYAxis(0, 10, "Count per feedback", kBottomMargin,
+                          kTopMargin);
+}
+
 void EventLogAnalyzer::CreateOutgoingTWCCLossRateGraph(Plot* plot) const {
   TimeSeries loss_rate_series("Loss rate (from packet feedback)",
                               LineStyle::kLine, PointStyle::kHighlight);
diff --git a/rtc_tools/rtc_event_log_visualizer/analyzer.h b/rtc_tools/rtc_event_log_visualizer/analyzer.h
index c055a12..5432cb5 100644
--- a/rtc_tools/rtc_event_log_visualizer/analyzer.h
+++ b/rtc_tools/rtc_event_log_visualizer/analyzer.h
@@ -115,6 +115,8 @@
                                     Plot* plot) const;
 
   void CreateOutgoingTWCCLossRateGraph(Plot* plot) const;
+  void CreateOutgoingEcnFeedbackGraph(Plot* plot) const;
+  void CreateIncomingEcnFeedbackGraph(Plot* plot) const;
   void CreateGoogCcSimulationGraph(Plot* plot) const;
   void CreateSendSideBweSimulationGraph(Plot* plot) const;
   void CreateReceiveSideBweSimulationGraph(Plot* plot) const;
@@ -144,6 +146,7 @@
   void CreateAccumulatedPacketsTimeSeries(Plot* plot,
                                           const IterableType& packets,
                                           const std::string& label) const;
+  void CreateEcnFeedbackGraph(Plot* plot, PacketDirection direction) const;
 
   const ParsedRtcEventLog& parsed_log_;
 
diff --git a/rtc_tools/rtc_event_log_visualizer/main.cc b/rtc_tools/rtc_event_log_visualizer/main.cc
index 78c09d3..ed865b3 100644
--- a/rtc_tools/rtc_event_log_visualizer/main.cc
+++ b/rtc_tools/rtc_event_log_visualizer/main.cc
@@ -244,7 +244,10 @@
         "simulated_neteq_preferred_buffer_size",
         "simulated_neteq_concealment_events", "simulated_neteq_preemptive_rate",
         "simulated_neteq_accelerate_rate", "simulated_neteq_speech_expand_rate",
-        "simulated_neteq_expand_rate"}}};
+        "simulated_neteq_expand_rate"}},
+      {"l4s",
+       {"incoming_bitrate", "outgoing_bitrate", "incoming_ecn_feedback",
+        "outgoing_ecn_feedback"}}};
 
   if (absl::GetFlag(FLAGS_list_plots)) {
     std::cerr << "List of registered plots (for use with the --plot flag):"