How to enable MSE & H2.64 support on YouTube for Firefox right now

When you open YouTube's HTML5 page in the most recent stable version of Firefox right now, you will notice that support is not available for all technologies listed on the page.

Support may be available for HTMLVideoElement, H.264 and WebM VP8, but not for Media Source Extensions, MSE & H.264 or MSE & WebM VP9.

A configuration option is available to enable Media Source Extensions and MSE & WebM VP9 right now in the Firefox browser.

To do so, load about:config in the browser's address bar and search for the term media.mediasource.enabled there. Double-click the preference to set it to true.

When you go back to YouTube's HMTL5 page afterwards, you will notice that only MSE & H.264 is listed as unsupported while all remaining options are supported.

firefox mse support

If you do not do that, you will only receive select resolutions for videos on YouTube when using the HTML5 video player. This is quite problematic as Google will force Firefox users to use the HTML5 video player from Firefox 33 on.

Mozilla has not enabled the feature by default yet, not even in the most recent Nightly version of Firefox. This is an indicator that the feature is not yet ready for prime time and that it may take a couple of release cycles before it will be enabled by default.

Most video resolutions become available after you enable Media Source Extensions in Firefox. What is still not supported afterwards however is MSE & H.264 which means that some videos may not play in all resolutions yet on the site.

Enable MSE & H.264

A new preference in Firefox Nightly 34 changes that however, so that support for all requested technologies is provided afterwards on YouTube.

Note: While the article concentrates on Google's video hosting platform, enabling support for MSE & H.264 will benefit users of the browser on other websites as well.

You need to create a new preference to do so:

  1. Type about:config and hit enter.
  2. Confirm you will be careful.
  3. Right-click and select New > Boolean.
  4. Name the preference media.mediasource.ignore_codecs.
  5. Set its value to True.

If you go back to YouTube's HTML page, you should see all six technologies listed as supported (in green).

firefox mse h264 support

Several bugs need to be resolved before the feature will be enabled directly by Mozilla for all users of the browser. You can check out the mediasource progress here.

This means that you may get hangs or experience other issues after enabling mp4 container support for Media Source Extensions in the browser.

Still, it is great to see that Mozilla is working on support for the feature in Firefox. It is unclear if it will manage to resolve all issues before Firefox 33 gets released, as it may result in an increase in support requests when Firefox users notice that YouTube is serving them only some resolutions.

Summary
Article Name
How to enable MSE & H2.64 support on YouTube for Firefox right now
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Description
Mozilla has enabled support for H.264 Media Source Extensions in Firefox 34. Find out how to enable the feature in Firefox right now.
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Responses to How to enable MSE & H2.64 support on YouTube for Firefox right now

  1. EuroScept1C July 25, 2014 at 4:56 pm #

    Right now best way to see videos on Youtube: IE11 and go to Safety-> ActiveX Filtering and enable it. It will play ALL videos on mp.4 format with DASH enabled, 1080p support and all. The most efficient way.

    • Rofl October 17, 2014 at 8:54 am #

      IE, are you crazy?

  2. pd July 25, 2014 at 7:54 pm #

    Running Aurora on Windows XP, I still don't have the Cisco h.264 codec. Any way to enable that?

    • Martin Brinkmann July 25, 2014 at 8:07 pm #

      Not yet, it appears to be only available in Nightly right now.

  3. geeknik July 26, 2014 at 1:27 am #

    MSE on YouTube still doesn't work properly. Seeking sometimes takes a lot of time, seeking back doesn't work at all and repeat also doesn't work. Just because you can flip the switch doesn't mean you're going to get MSE & H.264 support because according to a Mozilla developer, MP4 (H.264, etc.) aren't supported in MSE yet. They are concentrating on Webm on YouTube right now.

    Relevant bugs: https://bugzilla.mozilla.org/show_bug.cgi?id=881512, https://bugzilla.mozilla.org/show_bug.cgi?id=1024858

    My advice, don't force enable MSE for now unless you want a lot of YouTube headaches. ;)

  4. marius t July 26, 2014 at 9:48 am #

    No thanks I'll still use flash untill it really dies,my motto if it works don't mess with it!I'll force flash player with Youtube Center if I have to!

  5. Aramir September 1, 2014 at 10:47 am #

    I did that and lost sound on youtube videos .... No thanks

  6. bedsitter September 19, 2014 at 8:54 pm #

    I've done this under Firefox 32.02, but MSE & H.264 is still signed red.
    Don't know why this works for the author...

    • Petre September 22, 2014 at 12:26 am #

      It's the same for me under Ubuntu

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