Help us test You Tube on Firefox Nightly!

Marcia Knous


The implementation of Media Source Extensions (MSE) to support YouTube videos running in HTML5 has begun. We have enabled MSE in Firefox Nightly for YouTube on Windows and Mac, and over the past couple of weeks Mozilla engineers have been working hard on addressing the top bugs. We are looking to get this into the hands of our users as quickly as possible and in order to do that successfully we would like your help.

If you would like to participate, please install the latest Nightly,  go to, run videos and tell us about your experience. Note that this also covers You Tube videos that are embedded in other sites, not just videos on

Our testing etherpad has all the information to get started, including a template to file bugs if you find them:

Please feel free to ask questions in #qa on IRC. We look forward to your participation!

3 responses

  1. Ju Lee wrote on :

    I am new here, and just signed up the volunteer position in the web page. By following your email response, I visited the link to download the nightly build. I think there are a few questions.
    1. does it matter if my test environment (mostly OS type/version) is windows only or VM?
    2. your instruction said ‘go to youtube and tell us your experience of the video’. Can you clarify if this is a simple video playback testing, or definition/resolution, or audio/video sync, etc? if I know better what you expect, I can spend my time efficient.
    3. Can you also tell me how to reply the result to your team? is there any reporting tool? do you also need to see the test procedure?

    1. marcia wrote on :

      Ju Lee – Everything that Martijn mentions is accurate.

      Bugs in Bugzilla is the way to report any issues.

      When you are playing back videos, pay particular attention to:

      1. video hangs
      2. video stuttering
      3. audio not playing
      4. audio/video out of sync

  2. Martijn wrote on :

    Ju Lee,
    1. I don’t think it matters if you use a VM, as long as you use Mac or Windows, because MSE works only there.
    2. I think you should look out for things you would normally not expect while playing videos in Youtube. Those can be sync issues, which apparently are already bugs filed for. What bugs to expect, you could look at the already filed bugs on the link of the provided Etherpad.
    3. If you find issues that haven’t been reported before, you can file bugs for them. See the Etherpad for help.

    Let me know if you need more help. You can also email me, otherwise: martijn.martijn(at)gmail(dot)com