Disable HTML5 Media in Mozilla Firefox

If you are a Youtube addict like myself, then you must have noticed that some videos start playing in the HTML5 video format on their own. This happens even if you have opted out of the HTML5 video experiment in your Youtube account. This is very annoying because the HTML 5 videos do not play that smoothly on my computer. If you want to force Firefox to play all videos on Youtube in the Adobe Flash plugin only, then you can do so by making a few simple changes in the Firefox configuration. Here is how :

  1. Type about:config in the Firefox browser’s location bar.
  2. Click on the I’ll be careful, I promise! button to continue.

    Disable HTML5 Video in Firefox

  3. You would see a big list of Firefox configuration entries. Type media in the Search field to narrow down the list only to media related configuration entries. You would be able to find four values : media.ogg.enabled, media.wave.enabled, media.webm.enabled, media.windows-media-foundation.enabled.

    Disable HTML5 Video in Firefox

  4. Double-click on all these configuration entries to change their value to false. This would make Firefox report to Youtube (actually to all sites) that it cannot play HTML5 videos, forcing it to fallback to the Adobe Flash format of videos. Now if you open any video in Youtube, they would play only using the Adobe Flash plugin.
  5. If you do not notice the changes in Youtube, then you may try restarting the web browser or clearing out your browser cache.

The steps discussed above were tested successfully on latest version 23 of Firefox browser. Please note that this method not only disables the HTML5 video support from Youtube but also from all the sites that you access using Firefox. If you want to enable HTML5 video support for all websites again, then just follows the same steps – this time switching the values to true.


  1. Hi! Working on OS Windows 7, 64-bit, Mozilla Firefox – version 56.0 (64-bit)

    Don’t recognize Ultra High Qality in YouTube more than 1440 pixels!
    4K is NOT available in IDM menu…

    Thank you!

  2. not working on firefox 37…suddenly it started playing on html5 and I have the latest flash player as always…never had a problem with firefox about it not using the flash player until now…html5 sound is lower than flash and I hate it with all my hearth! please help! can’t find a solution anywhere!

  3. you can also remove cookies for youtube site, and it works. there might be a specific cookie to remove to disable html5.

  4. Thank you for a solution that does not involve “install yet another
    plugin”. It did the trick on my W7/Waterfox, which yesterday played HD
    content on youtube fine in Flash and this morning had HTML5 enforced and
    locked down to 360p.

  5. Dear Admin!

    bolshoi spasibo

    firefox 35 on mac x10.10.1 spontanously stopped playin “Video” fullscreen/flawless, seems to be html5 video related issue.

    not sure if ff35 or x.1 update messed it up

    fixed config according to this site


    media.ms-foundation entry of course absent on mäc.

    changed instead

    media.apple-mp4 false

    et voilà….

    now “video” stream flawless…or more precisly html5less via flash

    again… thanks a lot for saving my time & frustration

    Come to Berlin, I owe you some whateveryourfavoritedrinkis

  6. Thanks for this. For some reason HTML5 videos in Firefox 26 were locking up / freezing my computer. My computer is old though (512MB RAM, Windows 7 etc.)

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