--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -498,16 +498,20 @@ MediaDecoder::OnPlaybackEvent(MediaEvent
 {
   switch (aEvent) {
     case MediaEventType::PlaybackEnded:
       PlaybackEnded();
       break;
     case MediaEventType::SeekStarted:
       SeekingStarted();
       break;
+    case MediaEventType::Loop:
+      GetOwner()->DispatchAsyncEvent(NS_LITERAL_STRING("seeking"));
+      GetOwner()->DispatchAsyncEvent(NS_LITERAL_STRING("seeked"));
+      break;
     case MediaEventType::Invalidate:
       Invalidate();
       break;
     case MediaEventType::EnterVideoSuspend:
       GetOwner()->DispatchAsyncEvent(NS_LITERAL_STRING("mozentervideosuspend"));
       break;
     case MediaEventType::ExitVideoSuspend:
       GetOwner()->DispatchAsyncEvent(NS_LITERAL_STRING("mozexitvideosuspend"));

--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -3494,16 +3494,18 @@ MediaDecoderStateMachine::UpdatePlayback
     // period of the stream. So the time over the end should be corrected.
     bool loopback = false;
     if (mReader->IsLooped()) {
       MOZ_ASSERT(mReader->GetPeriod() > TimeUnit::Zero());
       clockTime = clockTime % mReader->GetPeriod().ToMicroseconds();
       if (clockTime < GetMediaTime()) {
         if (ShouldSeamlesslyLoop()) {
           loopback = true;
+          // Fire the `seeking` and `seeked` events to meet the HTML spec.
+          mOnPlaybackEvent.Notify(MediaEventType::Loop);
         } else { // Stop playing and decoding when looping is cancelled.
           StopPlayback();
           mAudioDataRequest.DisconnectIfExists();
           AudioQueue().Finish();
           mAudioCompleted = true;
         }
       }
     }

--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -115,16 +115,17 @@ class TaskQueue;
 extern LazyLogModule gMediaDecoderLog;
 
 enum class MediaEventType : int8_t
 {
   PlaybackStarted,
   PlaybackStopped,
   PlaybackEnded,
   SeekStarted,
+  Loop,
   Invalidate,
   EnterVideoSuspend,
   ExitVideoSuspend,
   StartVideoSuspendTimer,
   CancelVideoSuspendTimer,
   VideoOnlySeekBegin,
   VideoOnlySeekCompleted,
 };