Firefox Community Forum

(AI written summary of troubleshooting steps taken before making this support thread)

Firefox version: - 152.0.1 Release - 153.0 Nightly

OS: - Windows 11 build 26200

GPU: - NVIDIA GeForce RTX 4070 SUPER

Codec package: - Microsoft HEVC Video Extensions installed from Microsoft Store

Problem

Firefox does not expose HEVC playback support, causing Twitch to disable 1440p streams encoded with HEVC.

The same machine can play the same HEVC Twitch streams in Chrome immediately after installing HEVC Video Extensions.

Expected result

Firefox should report HEVC playback support and allow playback of HEVC streams, as Chrome does on the same system.

Actual result

Firefox reports HEVC as unsupported.

about:support:

codecSupportInfo: H264 SWDEC HWDEC VP9 SWDEC HWDEC VP8 SWDEC HWDEC AV1 SWDEC HWDEC HEVC NONE

Troubleshooting already performed

- Installed Microsoft HEVC Video Extensions - Rebooted Windows - Updated NVIDIA drivers - Verified hardware acceleration is enabled - Tested with a brand new Firefox profile - Tested with Firefox Nightly - Confirmed Chrome can play the same HEVC streams

Additional observations

Chrome: - Twitch 1440p becomes available immediately after installing HEVC Video Extensions - Twitch Stats for Nerds reports:

 hev1.1.6.L150.90.0.0.0.0.0

Firefox: - Twitch reports that the browser does not support the required resolution - 1440p remains greyed out - about:support continues to report HEVC NONE

Reproducible tests

Firefox console:

MediaSource.isTypeSupported('video/mp4; codecs="hev1.1.6.L150.90"')

Result: false

MediaSource.isTypeSupported('video/mp4; codecs="hvc1.1.6.L150.90"')

Result: false

navigator.mediaCapabilities.decodingInfo({

 type: "media-source",
 video: {
   contentType: 'video/mp4; codecs="hev1.1.6.L150.90"',
   width: 2560,
   height: 1440,
   bitrate: 8000000,
   framerate: 60
 }

})

Result: {

 supported: false,
 smooth: false,
 powerEfficient: false

}

For comparison:

MediaSource.isTypeSupported('video/mp4; codecs="av01.0.08M.08"')

Result: true

navigator.mediaCapabilities.decodingInfo({

 type: "file",
 video: {
   contentType: 'video/mp4; codecs="av01.0.08M.08"',
   width: 2560,
   height: 1440,
   bitrate: 8000000,
   framerate: 60
 }

})

Result: {

 supported: true,
 smooth: true,
 powerEfficient: true

}

Additional note

Setting:

dom.media.webcodecs.h265.enabled = true

causes HTML5 codec test (https://html5test.co/) to report H.265 support, but does not change:

- about:support - MediaSource.isTypeSupported() - MediaCapabilities.decodingInfo() - Twitch HEVC playback availability

Question

Is this a known issue with HEVC Media Source Extensions support on Windows 11 build 26200, or is there another requirement for Firefox to expose HEVC playback capability through MediaSource and MediaCapabilities when the Windows HEVC codec is installed and functioning in Chromium-based browsers?

Whenever I play something in the browser while connected to my TV by HDMI, the sound still comes out of the laptop speakers. This happened suddenly, without any discernible reason, and I can't seem to fix it. Everything else works, only content played from Firefox remains in the laptop speakers. I've checked my audio mixer, nothing seems amiss, I've updated Firefox and refreshed the application, still nothing. Hell, I've even tried different cables and HDMI ports, but nothing works. What could be the issue? Why did my audio suddenly stop working, and what can I do about it?

Trouble with streaming services(like youtube(only streams ), twitch, music streaming) on nightly Firefox Nightly 145.0a1 (2025-10-11) (x64) Cachy OS Binary from firefox.com

I have Win 11 dell computer that does not play or pick up sound from web sites videos .I checked and tested my sound using the Microsoft platform & buy playing a disc. It works OK

I am using FF desktop. All of a sudden, I get no sound through my laptop speakers when trying to watch videos (on YT and FB for example). I still get sound if I use external speakers through the 3.5" jack. I still get sound through other browsers, no matter if it's through the laptop speakers or external ones. So, it is definitely an FF problem. Sound works fine on all other media files on the laptop. Refreshing FF didn't fix it. Nor did reinstalling or restarting the laptop. I tried changing the autoplay settings as suggested in the help article, but still no laptop audio via FF. How can I fix this? Thanks

"I’ve been having trouble with choppy YouTube videos in Firefox. It happens on both Wi-Fi and Ethernet connections. My system is running Windows 10, and I’ve already tried disabling hardware acceleration and clearing my browser cache. The issue persists even when I’m in Safe Mode. I’m using the latest version of Firefox (XX.XX). Any suggestions on how to fix this?"

I think everyone knows how to get out of full screen mode by now, so can you either remove it or let us disable that little box that always shows when you go full screen for a video?

Recently I had a problem with Firefox opening a second icon on my Macbook. In order to fix it, I uninstalled and then re-downloaded Firefox. I tried to put everything back to the way it was before but I still have a problem with some websites not playing video. Most notably, Instagram and Blue Sky. I have attached screen shots. I have set Firefox to playback videos automatically but this has had no affect. Can anyone help?

Videos in YouTube play at about 50% brightness in full screen and not full screen, unless hardware acceleration is turned off, my mouse is hovering over an auto play thumbnail, or when the video is not in full screen and I open the right click context menu on the video.

I have an AW3225QF HDR monitor and an RTX 5070ti

Hello, I am currently using windows 11 with firefox 149.0. Regardless of what website I use (youtube. steam etc), the browser struggles to establish consistent connection to my bluetooth earbuds. It connects for one moment, but then soon the volume goes out and eventually it disconnects. Though it would reconnect soon, the cycle just keeps ongoing. I have experimented with other apps and browsers, as well as multiple bluetooth earbuds of other brands to be sure that it is a firefox issue. I have checked the volume mixer menu to ensure that there is nothing wrong. I have also made sure that my drivers are all up to date with no issue. But the issue still persists.

When I open Facebook in Firefox 150.0.1 with no extensions then move the cursor over a video, that video automatically plays.

Preferences | Privacy and Security | Browser Privacy | Permissions | Autoplay | Default is set to Block Audio and Video yet videos still automatically play.

Since the last update, I believe, because this error occurs constantly and with EVERY video. This is often, not always, the case immediately after updating FF. Now it was fine for a while, but now it's so bad that I'm having trouble watching YT videos properly. Reason: Browser open, logged in to YT. I click on a video to play - video opens, plays maybe 10 to 20 seconds, then playback stops spinning top, I also found out during the last glitch after update that if I switch the resolution briefly, higher or lower doesn't matter - important is to leave the current resolution and switch to another one. And oh wonder - immediately, instantly with the change, the video starts playing. If I wait for this - without doing anything myself, it sometimes takes 30 - 40 seconds for the video to start ... sometimes it just "hangs" ... This is extremely annoying - if it doesn't work, I have to switch browsers... What is also extremely annoying is that it occurs almost regularly after an update ... until the next one possibly, for unknown reasons, does not fix the error, but sometimes mitigates it. Now, however, the disruption/interruption is so massive and totally annoying that I'm thinking of switching. I'm just tired of it ...

• • • Translated with www.DeepL.com/Translator (free version) ***

Since the last update, I believe, because this error occurs constantly and with EVERY video. This is often, not always, the case immediately after updating FF. it was fine for a while, but now it's so bad that I'm having trouble watching YT videos properly. Reason: Browser open, logged in to YT. I click on a video to play - video opens, plays maybe 10 to 20 seconds, then playback stops spinning gyro, I also found out during the last glitch after update that if I switch the resolution briefly, higher or lower doesn't matter - important is to leave the current resolution and switch to another one. And oh wonder - immediately, instantly with the change, the video starts playing (for a while at least maybe 5 Minutes maybe 30 Sek... i´m done with FireFox ...) If I wait for this - without doing anything myself, it sometimes takes 30 - 40 seconds for the video to start ... sometimes it just “hangs” ... This is extremely annoying - if it doesn't work, I have to switch browsers... What also bothers me extremely is that it occurs almost regularly after an update ... until the next one possibly, for unknown reasons, does not fix the error, but sometimes mitigates it. Now, however, the disruption/interruption is so massive and totally annoying that I'm thinking of changing. I'm just tired of it ... Please fix it or shoot me ... any suggestions ??

I've freshly reinstalled Windows 11 and after trying to access and watch a movie on any of these sites I get an error (see the pictures).

Browser version: 137.0.1 (64 bit) Widevine version: 4.10.2891.0

Already tried to disable/enable DRM. Already reinstalled firefox. Already manually installed widevine. No clue what could be causing this issue.

This is the link to the video that will not play in FireFox. https://www.swingtechnologies.com/UploadVideos/clarkj@pobox.com/S200629_019 B.mp4

Good evening Mozilla,

Well I am facing an issue, no sound coming from any website like netflix or youtube or prime from mozilla browser.

Could you please fix it for me.

Regards