Firefox Community Forum

I just upgraded Firefox to version 156.0.2.

It no longer plays mp4 content from a website. It says "No video with supported format and mime type found".

This used to be OK.

When i go to fullscreen from default view on YouTube, the screen becomes grey but the video is still playing and the audio is working fine. However, i can go to fullscreen just fine if im in cinema mode. How do i fix this?

All of a sudden all of the videos I watch on YouTube with Firefox are defaulting to mute on my Macbook. I haven't made any changes to settings, etc. I don't have a YouTube account so I can't make any changes there anyway. I am having to unmute each video before I watch it.

Audio doesn't work with Firefox. This appears to be ONLY a Firefox problem. Headphones work with Edge. Computer speakers work. In Windows settings, testing audio works. But when I attempt to listen to something in Firefox, there is no sound at all.

I just switched to a new PC (Windows 11) and when using Firefox to watch videos, the audio fades in briefly instead of starting instantly. This happens with youtube, prime video, netflix etc. I have tested in Edge and this does not occur. I am using a bluetooth headset. I haven't been able to find anything about this online so open to any help.

Постоянное отображение панели задач (до тех пор, пока не нажму на иконку браузера на панели дважды. Повторяется с каждым заходом в режим "на весь экран" ), при просмотре видео, в браузере, в формате "на весь экран" с версии 156.0. в других браузерах подобной проблемы нет, только в Firefox. Прикладываю скрин визуального отображения проблемы. С настройками самой панели задач проблем нет, перепроверял.

Please help me as i want to record some gameplay but it keeps getting squished & it is pissing me off. I have asked on reddit & people were unhelpful & telling me to just buy another computer. this is annoying as it is causing me when playing games it causes text to be unreadable at times. Thanks in advance.

Tell me why I have no sound on Firefox and how to fix it. I do have sound on DuckDuckGo and AVG Secure Browser. I have checked my sound setting 55% and not muted. I have shut down and started laptop, still no sound. I checked Firefox updates and am good.

I get a "Sorry, the video player failed to load.(Error Code: 104153)" error when clicking links from a search for a video, if that video is available on YouTube it opens and plays just fine, not from other websites though - and it should. Fix?

Hello. uz vase roka mi plays videos without sound on Facebook. I tried to figure out why in the settings, but I failed. on other sites, the sound works. what could be the problem?

Hi,

two days ago, video embeds on Twitter stopped working in Firefox. Please help me troubleshoot the issue, so that I can either fix it myself, or present enough evidence to file a proper bug report.

Affected version: FF 140 ESR. I had some 140.7 installed when the error first happened, but have upgraded to firefox-esr_140.10.1esr-1_amd64 since. Didn't fix the problem. *Not* a snap package, regular .deb!

Affected OS: Ubuntu 26.04 LTS, not a fresh install but upgraded from 24.04 instead (which itself was upgraded from 22.04).

Symptoms: Videos on X (and Facebook) no longer play, the preview image is there for a split second, then an error appears. Video on for example Youtube is fine, though. Local players like VLC also do work as expected. Video on X worked under 26.04 before this happened.

The issue likely started when removing surplus packages and metapackages from the upgrade. According to synaptics, this is the complete list of packages removed: augeas-lenses bomber bovo clevis clevis-luks db-util db5.3-util dolphin-dev gir1.2-freedesktop-dev gir1.2-glib-2.0-dev girepository-tools gostsum granatier guestfish guestfs-tools guestmount icu-devtools jose kapman katomic kblackbox kblocks kbounce kbreakout kdegames kdegames-mahjongg-data-kf6 kdiamond kfourinline kgeography kgeography-data kgoldrunner kigo killbots kiriki kjumpingcube klickety klines kmahjongg knavalbattle knetwalk knights kolf kollision konquest kreversi kshisen ksirk ksnakeduel kspaceduel ksquares ktuberling ktuberling-data kubrick kubuntu-web-shortcuts ldmtool libaom-dev libarchive-tools libaugeas0 libblkid-dev libconfig11 libdbus-1-dev libdlt3 libffi-dev libfmt-dev libfontconfig1-dev libfribidi-dev libgd-perl libgio-2.0-dev libgio-2.0-dev-bin libglib2.0-dev libglib2.0-dev-bin libgraphite2-dev libguestfs-perl libguestfs-tools libguestfs0t64 libharfbuzz-cairo0 libharfbuzz-dev libhivex0 libicu-dev libjose0 libjson-glib-dev libjxr-tools libjxr0t64 libkdegames6private6 libkmahjongg6 libldm-1.0-0t64 libmosquitto1 libmount-dev libosinfo-1.0-0 libosinfo-l10n libpcre2-dev libpixman-1-dev libpolkit-gobject-1-dev libpsl-dev libpwquality-tools libpython3-dev libpython3.14-dev libselinux-dev libsepol-dev libspdlog-dev libsqlite3-dev libssh-dev libstd-rust-dev libstring-shellquote-perl libsys-virt-perl libsysprof-capture-4-dev libsystemd-dev libtirpc-dev libusb-0.1-4 libusb-1.0-0-dev libusb-1.0-doc libusb-dev libvirt-common libvirt0 libwebsockets19t64 libwhoopsie-preferences0 libwhoopsie0 libwin-hivex-perl libx265-dev libxdo-dev libxdo3 libxft-dev libxkbcommon-dev libxrender-dev libyara10 lskat lskat-data mosquitto mosquitto-clients native-architecture osinfo-db palapeli palapeli-data picmi qml6-module-org-kde-games-core skladnik supermin whoopsie whoopsie-preferences I don't think they are related (libx265 and libaom are only the -dev packages), but this is the only system-wide change on that day that I can remember. I of course tried re-installing these, but this also doesn't fix the problem.

On my journey of fixing this myself, I also asked the all-hallucinating knowledge randomizer frontend of OpenAI, which made me check a couple generic spots on my system and in FF itself.

ffmpeg -codecs | grep -E "h264|hevc|vp9|av1" ffmpeg version 8.0.1-3ubuntu2 Copyright (c) 2000-2025 the FFmpeg developers

 built with gcc 15 (Ubuntu 15.2.0-13ubuntu3)
 configuration: --prefix=/usr --extra-version=3ubuntu2 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --disable-pocketsphinx --disable-libcaca --disable-libmfx --disable-omx --enable-gnutls --enable-libaom --enable-libass --enable-libbs2b --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libharfbuzz --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-openal --enable-opencl --enable-opengl --disable-sndio --enable-libvpl --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-ladspa --enable-libbluray --enable-libdvdnav --enable-libdvdread --enable-libjack --enable-libjxl --enable-libpulse --enable-librabbitmq --enable-librist --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libx264 --enable-libzmq --enable-libzvbi --enable-lv2 --enable-sdl2 --enable-libplacebo --enable-librav1e --enable-librsvg --enable-shared
 WARNING: library configuration mismatch
 avcodec     configuration: --prefix=/usr --extra-version=3ubuntu2 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --disable-pocketsphinx --disable-libcaca --disable-libmfx --disable-omx --enable-gnutls --enable-libaom --enable-libass --enable-libbs2b --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libharfbuzz --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-openal --enable-opencl --enable-opengl --disable-sndio --enable-libvpl --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-ladspa --enable-libbluray --enable-libdvdnav --enable-libdvdread --enable-libjack --enable-libjxl --enable-libpulse --enable-librabbitmq --enable-librist --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libx264 --enable-libzmq --enable-libzvbi --enable-lv2 --enable-sdl2 --enable-libplacebo --enable-librav1e --enable-librsvg --enable-shared --enable-version3 --disable-doc --disable-programs --disable-static --enable-libaribb24 --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc --enable-libsmbclient
 libavutil      60.  8.100 / 60.  8.100
 libavcodec     62. 11.100 / 62. 11.100
 libavformat    62.  3.100 / 62.  3.100
 libavdevice    62.  1.100 / 62.  1.100
 libavfilter    11.  4.100 / 11.  4.100
 libswscale      9.  1.100 /  9.  1.100
 libswresample   6.  1.100 /  6.  1.100
DEV.L. av1                  Alliance for Open Media AV1 (decoders: libdav1d libaom-av1 av1 av1_cuvid av1_qsv) (encoders: libaom-av1 librav1e libsvtav1 av1_nvenc av1_qsv av1_vaapi av1_vulkan)
DEV.LS h264                 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (decoders: h264 h264_v4l2m2m h264_qsv h264_cuvid) (encoders: libx264 libx264rgb h264_nvenc h264_qsv h264_v4l2m2m h264_vaapi h264_vulkan)
DEV.L. hevc                 H.265 / HEVC (High Efficiency Video Coding) (decoders: hevc hevc_qsv hevc_v4l2m2m hevc_cuvid) (encoders: libx265 hevc_nvenc hevc_qsv hevc_v4l2m2m hevc_vaapi hevc_vulkan)
DEV.L. vp9                  Google VP9 (decoders: vp9 vp9_v4l2m2m libvpx-vp9 vp9_cuvid vp9_qsv) (encoders: libvpx-vp9 vp9_vaapi vp9_qsv)
DEAIL. wmav1                Windows Media Audio 1

-> ffmpeg is installed, version 8, av1 and hevc support seems present. The sparse advice from google results (similar thing in a Gentoo forum I think) on installating ffmpeg4.4 is no longer viable. --- apt list --installed | grep libavcodec

libavcodec-dev/resolute,now 7:8.0.1-3ubuntu2 amd64 [installed] libavcodec-extra62/resolute,now 7:8.0.1-3ubuntu2 amd64 [installed,automatic] libavcodec-extra/resolute,now 7:8.0.1-3ubuntu2 amd64 [installed]

(libavcodec62 non-extra was installed before, didn't change anything) --- apt list --installed | grep libaom*

libao-common/resolute,resolute,now 1.2.2+20180113-1.2ubuntu2 all [installed,automatic] libao4/resolute,now 1.2.2+20180113-1.2ubuntu2 amd64 [installed,automatic] libaom3/resolute,now 3.13.1-2 amd64 [installed,automatic] --- FF about:support in the codec section says this: Codec Support Information Codec Name Software Decoding Hardware Decoding H264 Unsupported Supported VP9 Supported Supported VP8 Supported Supported AV1 Supported Unsupported HEVC Unsupported Supported AAC Unsupported Unsupported MP3 Supported Unsupported Opus Supported Unsupported Vorbis Supported Unsupported FLAC Supported Unsupported Wave Supported Unsupported --- vainfo Trying display: wayland libva info: VA-API version 1.23.0 libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/iHD_drv_video.so libva info: Found init function __vaDriverInit_1_22 libva info: va_openDriver() returns 0 vainfo: VA-API version: 1.23 (libva 2.22.0) vainfo: Driver version: Intel iHD driver for Intel(R) Gen Graphics - 26.1.2 () vainfo: Supported profile and entrypoints

     VAProfileMPEG2Simple            : VAEntrypointVLD
     VAProfileMPEG2Main              : VAEntrypointVLD
     VAProfileH264Main               : VAEntrypointVLD
     VAProfileH264Main               : VAEntrypointEncSliceLP
     VAProfileH264High               : VAEntrypointVLD
     VAProfileH264High               : VAEntrypointEncSliceLP
     VAProfileJPEGBaseline           : VAEntrypointVLD
     VAProfileJPEGBaseline           : VAEntrypointEncPicture
     VAProfileH264ConstrainedBaseline: VAEntrypointVLD
     VAProfileH264ConstrainedBaseline: VAEntrypointEncSliceLP
     VAProfileVP8Version0_3          : VAEntrypointVLD
     VAProfileHEVCMain               : VAEntrypointVLD
     VAProfileHEVCMain10             : VAEntrypointVLD
     VAProfileVP9Profile0            : VAEntrypointVLD
     VAProfileVP9Profile2            : VAEntrypointVLD

--- running with MOZ_DISABLE_HW_DECODE=1 firefox -> no change --- A fresh profile shows the same issues, so this should not be config-related in terms of Firefox --- Safe mode on my standard profile also doesn't change anything --- running with MOZ_LOG="PlatformDecoderModule:5" firefox -> also no change, but now on every try to play a video, these three lines are spammed: [Child 2326924: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/avc [Child 2326924: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/av1 [Child 2326924: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/hevc

On other websites, the occasional [Child 2330726: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type audio/mp4a-latm or [Child 2331802: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/vp8

is added.

Some time close to starting FF, this block is presented: [Utility 2331783: Main Thread]: D/PlatformDecoderModule PDMInitializer, Init PDMs in Utility process [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFMPEG: version: 0x200, macro: 62, micro: 101, isFFMpeg: yes [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFVPX: Link result: Success [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder rejects requested type 'video/avc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule Agnostic decoder rejects requested type 'video/avc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp9' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp9' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp8' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp8' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/av1' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/av1' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder rejects requested type 'video/hevc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule Agnostic decoder rejects requested type 'video/hevc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder rejects requested type 'audio/mp4a-latm' [Utility 2331783: Main Thread]: D/PlatformDecoderModule Agnostic decoder rejects requested type 'audio/mp4a-latm' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/mpeg' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/mpeg' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/opus' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/opus' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/vorbis' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/vorbis' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/flac' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/flac' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/x-wav' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/x-wav' [Parent 2331581: Main Thread]: D/PlatformDecoderModule Broadcast support from 'Utility Generic', support=H264 NONE VP9 SW VP8 SW AV1 SW HEVC NONE AAC NONE MP3 SW Opus SW Vorbis SW FLAC SW Wave SW

Back in FF 140.7, I also got these lines, but they're no longer present in 140.10 or flags have changed, I don't know: [Child 2238921, MediaDecoderStateMachine #1] WARNING: Decoder=7329b02ba900 state=DECODING_METADATA Decode metadata failed, shutting down decoder: file ./dom/media/MediaDecoderStateMachine.cpp:371 [Child 2238921, MediaDecoderStateMachine #1] WARNING: Decoder=7329b02ba900 Decode error: NS_ERROR_DOM_MEDIA_METADATA_ERR (0x806e0006): file ./dom/media/MediaDecoderStateMachineBase.cpp:168

--- The troubleshooting info below this text box says this somewhere:

"name": "AV1_HW_DECODE",
         "description": "AV1 hardware decoding",
         "status": "blocklisted",
         "log": [
           {
             "type": "default",
             "status": "available"
           },
           {
             "type": "env",
             "status": "blocklisted",
             "failureId": "FEATURE_FAILURE_VIDEO_DECODING_MISSING",
             "message": "#BLOCKLIST_FEATURE_FAILURE_VIDEO_DECODING_MISSING"
           }

Open to suggestions on where to dig deeper next...thank you!

First of all I'm doing my testing in:

AMD Ryzen 7 7730u Windows 11 24H2 Firefox 133.0.3 Haylou GT1 Pro Bluetooth earbuds

I'm using jellyfin on web. And I listen to music on it, the problem I'm facing is... The moment I disconnect and reconnect my earbuds, the audio stops, the tab says "PLAYING" but no audio is played, I can press pause and play an infinite number of times but does not work UNTIL I reload the tab, then the audio comes back. Wouldn't be a big deal except for the fact everytime I have to reload, jellyfin does not save the current playlist so I have to create it again.

I tested this on the latest version of Microsoft Edge and it works with no problem there, I disconnect earbuds, audio stops, reconnect them and audio resumes, without even having to press play. The problem is something with firefox and the way it selects audio devices I guess?

I send a screenshot of firefox with the tab "PLAYING" but not actually doing it, and I send a logging file that I created using about:logging and the preset "Media playback", starting when I play media, disconnect bluetooth device, reconnect and can't hear anything

Logging file: https://pastebin.com/8CXn7bkv

If you need more info, please tell me. Greetings!

Has anybody else experienced a similar problem? Or can you help me trouble shoot this issue please?

I'm busy playing audio in a tab of the browser. The sound quality is good (rich, full, deep). Next, I open a new window by any means (Ctrl+N / Open link in new window / Menu > New window) As the new window appears, the current audio playback becomes tinny / lower quality. After a 3 seconds, the normal good sound quality starts again.

I'm currently using Bluetooth connected headphones and this happens on different headphones. I have to find some wired headphones first before I can try that. This happens with every new window that I open, regardless of the number of open tabs in current windows or how many previous open windows I already have. This happens regadless if audio enhancements of the output device are enabled or not. Spatial sound is set to off. Windows is set to 'do nothing' & will not adjust the volumes of different sounds when I'm using my PC to place or receive telephone calls.

OS: Windows 11 with latest patches Firefox: latest & older builds Hardware drivers: All manufacturer drivers applied

PS I can replicate this issue by changing between the 'Playback' & 'Recording' tab in the Sound Control Panel applet. That is to say, the same decrease in audio quality happens when I change from the Playback tab to the Recording tab. Audio quality improves again when I change from the Recording tab to the Playback tab https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2026-09-12-15-38-23-1accad.png

PPS My new windows are set to open on 'about:support'

PPPS Can't reply to previously archived question : https://support.mozilla.org/en-US/questions/1525613