--- a/dom/media/MediaPrefs.h
+++ b/dom/media/MediaPrefs.h
@@ -115,17 +115,17 @@ private:
   DECL_MEDIA_PREF("media.libavcodec.allow-obsolete",          LibavcodecAllowObsolete, bool, false);
 #endif
 #ifdef MOZ_FFVPX
   DECL_MEDIA_PREF("media.ffvpx.enabled",                      PDMFFVPXEnabled, bool, true);
 #endif
 #ifdef XP_WIN
   DECL_MEDIA_PREF("media.wmf.enabled",                        PDMWMFEnabled, bool, true);
   DECL_MEDIA_PREF("media.decoder-doctor.wmf-disabled-is-failure", DecoderDoctorWMFDisabledIsFailure, bool, false);
-  DECL_MEDIA_PREF("media.wmf.vp9.enabled",                    PDMWMFVP9DecoderEnabled, bool, false);
+  DECL_MEDIA_PREF("media.wmf.vp9.enabled",                    PDMWMFVP9DecoderEnabled, bool, true);
   DECL_MEDIA_PREF("media.wmf.low-latency.enabled",            PDMWMFLowLatencyEnabled, bool, false);
   DECL_MEDIA_PREF("media.wmf.decoder.thread-count",           PDMWMFThreadCount, int32_t, -1);
   DECL_MEDIA_PREF("media.wmf.skip-blacklist",                 PDMWMFSkipBlacklist, bool, false);
   DECL_MEDIA_PREF("media.windows-media-foundation.max-dxva-videos", PDMWMFMaxDXVAVideos, uint32_t, 8);
   DECL_MEDIA_PREF("media.windows-media-foundation.allow-d3d11-dxva", PDMWMFAllowD3D11, bool, true);
 #endif
   DECL_MEDIA_PREF("media.decoder.fuzzing.enabled",            PDMFuzzingEnabled, bool, false);
   DECL_MEDIA_PREF("media.decoder.fuzzing.video-output-minimum-interval-ms", PDMFuzzingInterval, uint32_t, 0);

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -340,17 +340,17 @@ pref("media.mp4.enabled", true);
 // just outputs blank frames/audio instead of actually decoding. The blank
 // decoder works on all platforms.
 pref("media.use-blank-decoder", false);
 #ifdef MOZ_WMF
 pref("media.wmf.enabled", true);
 pref("media.wmf.decoder.thread-count", -1);
 pref("media.wmf.low-latency.enabled", false);
 pref("media.wmf.skip-blacklist", false);
-pref("media.wmf.vp9.enabled", false);
+pref("media.wmf.vp9.enabled", true);
 pref("media.windows-media-foundation.allow-d3d11-dxva", true);
 pref("media.wmf.disable-d3d11-for-dlls", "igd10iumd32.dll: 20.19.15.4444, 20.19.15.4424, 20.19.15.4409, 20.19.15.4390, 20.19.15.4380, 20.19.15.4360, 10.18.10.4358, 20.19.15.4331, 20.19.15.4312, 20.19.15.4300, 10.18.15.4281, 10.18.15.4279, 10.18.10.4276, 10.18.15.4268, 10.18.15.4256, 10.18.10.4252, 10.18.15.4248, 10.18.14.4112, 10.18.10.3958, 10.18.10.3496, 10.18.10.3431, 10.18.10.3412, 10.18.10.3355, 9.18.10.3234, 9.18.10.3071, 9.18.10.3055, 9.18.10.3006; igd10umd32.dll: 9.17.10.4229, 9.17.10.3040, 9.17.10.2857, 8.15.10.2274, 8.15.10.2272, 8.15.10.2246, 8.15.10.1840, 8.15.10.1808; igd10umd64.dll: 9.17.10.4229, 10.18.10.3496; isonyvideoprocessor.dll: 4.1.2247.8090, 4.1.2153.6200; tosqep.dll: 1.2.15.526, 1.1.12.201, 1.0.11.318, 1.0.11.215, 1.0.10.1224; tosqep64.dll: 1.1.12.201, 1.0.11.215; nvwgf2um.dll: 10.18.13.6510, 10.18.13.5891, 10.18.13.5887, 10.18.13.5582, 10.18.13.5382, 9.18.13.4195, 9.18.13.3165; atidxx32.dll: 21.19.151.3, 21.19.137.1, 21.19.134.1, 20.19.0.32837, 20.19.0.32832, 8.17.10.682, 8.17.10.671, 8.17.10.661, 8.17.10.648, 8.17.10.644, 8.17.10.625, 8.17.10.605, 8.17.10.581, 8.17.10.569, 8.17.10.560, 8.17.10.545, 8.17.10.539, 8.17.10.531, 8.17.10.525, 8.17.10.520, 8.17.10.519, 8.17.10.514, 8.17.10.511, 8.17.10.494, 8.17.10.489, 8.17.10.483, 8.17.10.453, 8.17.10.451, 8.17.10.441, 8.17.10.436, 8.17.10.432, 8.17.10.425, 8.17.10.418, 8.17.10.414, 8.17.10.401, 8.17.10.395, 8.17.10.385, 8.17.10.378, 8.17.10.362, 8.17.10.355, 8.17.10.342, 8.17.10.331, 8.17.10.318, 8.17.10.310, 8.17.10.286, 8.17.10.269, 8.17.10.261, 8.17.10.247, 8.17.10.240, 8.15.10.212; atidxx64.dll: 21.19.151.3, 21.19.137.1, 21.19.134.1, 20.19.0.32832, 8.17.10.682, 8.17.10.661, 8.17.10.644, 8.17.10.625; nvumdshim.dll: 10.18.13.6822");
 pref("media.wmf.disable-d3d9-for-dlls", "igdumd64.dll: 8.15.10.2189, 8.15.10.2119, 8.15.10.2104, 8.15.10.2102, 8.771.1.0; atiumd64.dll: 7.14.10.833, 7.14.10.867, 7.14.10.885, 7.14.10.903, 7.14.10.911, 8.14.10.768, 9.14.10.1001, 9.14.10.1017, 9.14.10.1080, 9.14.10.1128, 9.14.10.1162, 9.14.10.1171, 9.14.10.1183, 9.14.10.1197, 9.14.10.945, 9.14.10.972, 9.14.10.984, 9.14.10.996");
 #endif
 #if defined(MOZ_FFMPEG)
 #if defined(XP_MACOSX)
 pref("media.ffmpeg.enabled", false);
 #else