--- a/dom/media/fmp4/MP4Decoder.cpp
+++ b/dom/media/fmp4/MP4Decoder.cpp
@@ -127,16 +127,22 @@ MP4Decoder::IsSupportedType(const MediaC
         continue;
       }
       if (codec.EqualsLiteral("flac")) {
         trackInfos.AppendElement(
           CreateTrackInfoWithMIMETypeAndContainerTypeExtraParameters(
             NS_LITERAL_CSTRING("audio/flac"), aType));
         continue;
       }
+      if (codec.EqualsLiteral("vp9") || codec.EqualsLiteral("vp9.0")) {
+        trackInfos.AppendElement(
+          CreateTrackInfoWithMIMETypeAndContainerTypeExtraParameters(
+            NS_LITERAL_CSTRING("video/vp9"), aType));
+        continue;
+      }
       // Note: Only accept H.264 in a video content type, not in an audio
       // content type.
       if (IsWhitelistedH264Codec(codec) && isVideo) {
         trackInfos.AppendElement(
           CreateTrackInfoWithMIMETypeAndContainerTypeExtraParameters(
             NS_LITERAL_CSTRING("video/avc"), aType));
         continue;
       }