How to Enable Media Source Extensions in Firefox

HTML5 brought forward many new things when it was first release a few years ago. The most talked about feature of HTML5 is its ability of playing videos and audio streams without having to require any third party plugins like Adobe Flash Player. While Firefox already supports many different features of HTML5, there are many new things are are being rolled out with each new version of this great web browser. In the latest release of Firefox – version 31, they have added a new HTML5 feature called Media Source Extensions that can make HTML5 video play much more interactively on a webpage.

The Media Source Extensions feature is not enabled by default in Firefox as of now. So you have make some changes in your Firefox browser settings to enable this feature. Here is how you can enable Media Source Extensions in Firefox:

  1. Open Firefox web browser. Type about:config in the address bar and press Enter.
  2. It will show you some warnings. Click on the “I’ll be careful. I promise” button to proceed. This will open a screen where all the Firefox configuration settings, their types and values will be displayed in form of a long list.
  3. Type mediasource in the search field to narrow down the configuration settings that we are interested in.Firefox Media Source Extensions
  4. Locate the setting named media.mediasource.enabled, double-click on it to toggle its value to true.
  5. That’s it. You can check your browser’s HTML5 video playing capabilities by visiting You should be able to see Media Source Extensions and MSE & WebM VP9 as enabled and working.Firefox Media Source Extensions

By enabling Media Source Extension you just giving an option to the websites to make use of this feature in your web browser. But if a website does not make use of this feature, then you will not notice any improvement in HTML5 video playback. As of now, only Youtube website is known to make use of Media Source Extensions when you watch videos in the HTML5 mode.

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