How to enable MSE and native HTML5 support in Firefox on Linux


Mozilla recently announced the release of Firefox 37 which comes with many new features. One of the most important features is native support for HTML 5. The new Media Source Extensions API that has been enabled allows native HTML5 playback on YouTube, essentially with this there is no need for Flash to use YouTube as everything should work correctly including live video.

The flip side is, as usual the feature is available for Mac and Windows users only. Unfortunately the MSE API hasn’t been enabled for Linux users who arguably needed it most given that half of us don’t run Flash and the half that do no longer get major Flash updates.

If you are a Linux user, you have to do that extra work to get things going.

Let’s get started.

Open Firefox and go to about:config page. Then press the button which says “i’ll be careful, I promise”.

Then in the search box type and hit enter. From the long list, look for the following and toggle them all to ‘true’:


Be sure to leave the following set to false:

Now visit the HTML5 page of YouTube and ensure that all items are ‘blue’ and not ‘red’.

firefox-html5Now go ahead and enjoy YouTube videos without having to worry about Flash.

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Free and Open Source software advocate. I've been enthusiastic about new technology for over half a decade and now I'm just waiting for the technological singularity. Post-Snowden, I've developed a dislike for surveillance meaning I use FLOSS religiously over proprietary alternatives. Amateur Astronomy is also a hobby of mine!
  • Will

    Thanks! Great article!

  • Aaron Franke

    Why is this not the default setting?

  • Anonymous

    Thanks a lot

  • MSE and WebM VP9 does not enable with these settings on Archlinux running FF 41.0.1

  • Ivan Sergiienko

    “Then in the search box type and hit enter”

    After that you also have to type media.fragmented, to get search results for