HTML5 Player

Enable HTML5 Video Firefox

• http://www.ghacks.net/2014/07/25/enable-mse-h2-64-support-youtube-firefox-right-now/
• https://www.cjross.net/using-the-html5-version-of-youtube-with-arch-linux/

about:config
media.mediasource.enabled

True

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:

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

Update: Linux userrs may change the following preferences as well:

    media.mediasource.mp4.enabled to true
    media.fragmented-mp4.* to true
    media.fragmented-mp4.use-blank-decoder to false

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