Firefox Community Forum

Hello,

I recently updated my Firefox browser to the latest version, 138.0.1 (64-bit), on Windows.

After the update, I noticed that when playing videos in fullscreen mode (for example, on YouTube or other video websites), the Windows taskbar (the bar at the bottom of the screen with the Start menu icon) does not hide automatically. This is affecting my fullscreen viewing experience.

Before updating to version 138.0.1, the Windows taskbar would hide correctly when entering fullscreen video.

I was wondering if anyone else has encountered a similar issue with the Windows taskbar not hiding, or if there are any suggested solutions to help resolve this problem.

Thank you for your help!

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.

"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?"

Hi,

How can I force Nightly to play a media type ? Per instance, the top main video here : https://www.lapresse.ca/international/asie-et-oceanie/2025-12-23/coree-du-nord/kim-jong-un-inaugure-un-complexe-hotelier-dans-une-station-de-montagne.php

Best regards iBenny

So, my problem is with HW acceleration in FF. Basically:

If its enabled: It causes graphical artifacts in videos [See screenshot]. If its disabled: It brings screen tear in to videos and autoscroll [Like if Vsync is disabled in games].

I tried safe mode, I tried reinstall of FF, I tried disabling and enabling extensions. I tried to set Vsync on in Nvidia control panel... the only thing that impact those bugs is HW acceleration in FF.

My drivers are up to date, my browser is up to date, yet there is such trouble.

Any ideas or solutions?

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

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!

This issue just appeared. Video will not play in Firefox. Windows10 PC, up to date with latest versions, as is Firefox. There is no error message or code. Just the spinning wheel. I see other people are having the same issue but I haven't seen a solution. Any ideas or help appreciated.

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?

Hallo everyone,

after many hours of Google search and trying many changes in the "about:config" section im done with things to try so my last chance is here.

The problem i have is that videos dont play if i mouseover the firefox window or tab i.E. on the windows taskbar. The video will only start to play if i click on the window/tab and that window/tab is the "active" one im looking at.

It worked fine before but some firefox update f***ed this up (and yes the official firefox updates are the only thing that changed), no i dont know which update it was because i didnt recognize the problem right away.

The autoplay option is set to allow media and audio.

The weird thing is that when i open a video in the vlc player and do the mouseover, everything works just fine. So my conclusion is that some setting was messed up on the new firefox version.

Some data of my pc, everything is updated: - Windows 11 Pro - CPU is AMD Ryzen 7 5800X3D 3,4GHz - GPU is AMD Radeon RX 7900XT - RAM is 32GB DDR4 CL16 - Internet is wired connection with 250K speed - Firefox Version is 137.0.1

Sorry for my bad english and thank you in advance.

Earlier today the audio on Firefox stopped working. I have tried disabling extensions, checked output devices, reinstalled and it still doesn't work. Please Help. The Version is 150.0.1

Windows just had an update, in that when I did it now Firefox has no sound at all in Youtube, Disney plus or any other site.

Now I did my own trouble shooting, games have sounds, my music player (winamp) has sound, I downloaded chrome and I oped volume mixer and played a video in that, there was sound.

I do the same thing in firefox and there is no sound, and in volume mixer where the lines go up showing the volume as it plays, it did it for chrome but not Firefox.

So there is no issue with my head set, my computer or my sound, it is firefox alone.

What the title says. Firefox just isn't playing any sound whatsoever.

Troubleshooting:

• Volume mixer indicates that Firefox is using my speakers, along with all other apps. When playing a YouTube video, the green bar is not bouncing. However, all other programs that play sound do so successfully and their green bars are bouncing (see attachment).

• Other web browsers play sound successfully.

• Restarting Firefox and my computer did not help.

• Switching the default sound device and changing back did not help.

• Changing to headphones made no change.

• Tabs are not muted.

• Autoplay settings in about:preferences showed that audio and video were disabled, however changing this setting to allow video and audio, then restarting both Firefox and the computer did not fix the problem. I have no idea how that setting was even changed to begin with. O_o

• Started Firefox in troubleshooting mode; still no sound.

• Started Firefox in a different profile; still no sound.

• Started Firefox in private mode; still no sound.

• Tried ending the audiodg.exe process in task manager and restarted; still no sound.

• Double checked media.autoplay.blocking_policy, was set to 0.

• Double checked media.block-autoplay-until-in-foreground -- changed from true to false, restarted Firefox; still no sound.

• Disabled hardware acceleration; still no sound.

• Refreshed Firefox; still no sound.

• Complete uninstall, including the usage of BCUninstaller to uninstall "leftovers". Reinstalled. Still no sound.

I have Apollo installed on my computer and I've reached out to them before for similar issues, but the dev was insistent that Apollo does not cause sound issues. I'm somewhat sceptical, but they're not being helpful at all so I thought I'd ask here, and disclose usage of Apollo so that all bases are covered.

Thank you for your time.

Reposting until I get help from someone. Windows/desktop. On Google Chrome, any streaming website I used with autoplay enabled would KEEP full screen mode ON after changing episodes. It would automatically go to a new page with the following episode and remain full screen. Why doesn't Firefox have this feature?? I'm seriously considering going back to Google Chrome for this one small feature. Every time I had any streaming service playing with autoplay enabled, I didn't have to manually select the full screen option every time. I am having to stand up and manually click full screen function. Every. Single. Time. Somebody please help me if there's a way to active that function.

I have HDR working in Proton games and mpv fine (using Plasma 6.4 / Wayland)

I enabled HDR in Firefox (gfx.wayland.hdr), and HDR content works in YouTube fine ( looks amazing!) however.. I have an issue in that all non HDR content doesn’t show any video (I have sound) just a green sceen (see screen shot) including all ads.

Any idea how to work round this ?

I have AMD 7800 GPU .

Cheers

Hi, when I launch a custom video player on a certain site and go into full screen mode, and then want to exit it through ESC, I can’t do it and the picture freezes. I went to the browser console, and it gave me this error: Uncaught (in promise) TypeError: Not in fullscreen mode

   cancelFullScreen https://interneturok.ru/assets/custom-2dc6965f3c367b4e4590249bd2036dfc.js:578
   hotkeys https://interneturok.ru/assets/custom-2dc6965f3c367b4e4590249bd2036dfc.js:675
   dispatcher https://interneturok.ru/assets/custom-2dc6965f3c367b4e4590249bd2036dfc.js:131|

The technical support of that site told me to write to the browser support, I understood the problem is not on their side. I tried everything and went through incognito mode, the problem did not go away. Give me some advice or maybe the problem is with this site and not with the browser, I also tried to launch this video player through Google Chrome and there were no problems there

This is what the GPTchat wrote about the error from the console: Yes, this error is directly related to exiting fullscreen mode. It says that the custom-2dc6965f3c367b4e4590249bd2036dfc.js script on the site is trying to exit fullscreen when the browser thinks it is no longer in it.

That is, Firefox has already exited fullscreen mode, but the player itself "thinks" that it is still there. Therefore, when you press Esc, the script calls cancelFullScreen(), and the browser throws the error "Not in fullscreen mode".

Plus screen Error

The video from certain sites(not one, but multiple ones) plays as gibberish. Attached a sample from amazon prime. Tried the following

• System restart
• Bios/Firmware update
• Display driver update
• Windows refresh

The issue seems very much localized to Firefox and not seen in any other browsers.

Since Flathub list the org.mozilla.firefox app as official, i hope this is the correct support channel.

Recently i switched from distro specific package managers to flatpak as my application provider. The firefox flatpak won't play most embedded Video/Media on applications like in-browser fediverse clients, forums, blogs or wikis. Youtube works without any issues, Twitch is fine until there is an adbreak. Then it sometimes stops with the supported format/mime error (screenshot appended), only recoverable by cache-dismissive reload.

I used this Article https://support.mozilla.org/en-US/kb/audio-and-video-firefox and the links it contains to debug without any success. None of these samples play. just shows supported format/mime error https://test-videos.co.uk/bigbuckbunny/mp4-h265 At this test website 1. and 3. example won't play. I provided a screenshot before and after trying to click play on all the examples. https://www.tekeye.uk/html/html5-video-test-page

Contrary to the observed behavior about:support#media claims Software Decoding supported for everything except HEVC.

Chromium Flatpak has no such issues. So i copy the video url and play it with chromium. You can see: dire times.

!. link to youtube only flashes then plays only audio. Full video requires opening link in a new private browser window

2. Typing into search bar for Duck Duck Go in new tab page types directly into active bar...

3. Active bar is no longer at the top but is in Bookmarks toolbar...

I suspect some update problem.