Youtube HTML5 is not working anymore after I upgraded to Firefox Nightly 57.0a1. Anyone got it to work?

On the same machine (Ubuntu 16.04) I have Chromium browser, where all the Youtube HTML5 options are working.

Also, it seems impossible to make Youtube work with the Flash player on Firefox. I tried the "official" way by turning media.autoplay.enabled to false. I also tried to change the user agent to Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:21.0) Gecko/20130331 Firefox/21.0 - both did nothing to convince Youtube to use Flash!

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Here is what I have tried so far:

I have run

sudo apt-get install ubuntu-restricted-extras

as was recommended here https://askubuntu.com/a/436336

but it did not change the status on the Firefox Youtube page below (so why was that stuff needed?)

Also I have set the following in Firefox about:config

media.mediasource.enabled; true
media.mediasource.format-reader; true
media.mediasource.format-reader.webm; true
media.mediasource.mp4.enabled; true
media.mediasource.webm.enabled; true

media.fragmented-mp4.enabled; true
media.fragmented-mp4.exposed; true
media.fragmented-mp4.ffmpeg.enabled; true
media.fragmented-mp4.gmp.enabled; true
media.fragmented-mp4.use-blank-decoder; false

as appears here https://www.youtube.com/watch?v=OUfCsSch8Zk although it looks outdated: some of the preferences did not exist, so I tried to add them anyway... but it changed nothing on the Firefox Youtube page below.

What does this browser support?


Firefox Nightly (running in safe mode)

57.0a1 (2017-08-03) (64-bit)

enter image description here

enter image description here


Chromium 59.0.3071.109 Built on Ubuntu , running on Ubuntu 16.04

enter image description here


By installing the nightly's builds, you like to live dangerously

The actual stable version is the 54, and you are with the version 57... Just to let you know that nightly build version are mostly experimental version.

in All cases going on the Firefox website there > https://www.mozilla.org/en-US/firefox/new/ might help you alot. Then click on the blue button "Refresh FireFox" beside the green button it might help you a lot by refrefreshing firefox

or go there > https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings?utm_source=mozilla.org&utm_medium=referral&utm_campaign=learn-more-link To do it from the browser itself

Note: your add-ons will be reset as well as your settings, but you will still have your passwords and so.

EDIT: If it's for the container tabs, it's already in the "normal" Firefox (V 54), but it's disabled (false) by default > So, you can instal the V54 stable then go to the about:config pref privacy.userContext.enabled and set it to 'true' by double clicking on the line, I just did it ;) (that's a cool feature BTW) you might need to restart firefox


EDIT 2 : Might it be possible that it come from your distro too? I am on ubuntu-MATE (the distro > https://ubuntu-mate.org/) and have not problem at all (see below the screen shot) and the FireFox i am using is the one installed by default on the distro and flash is not installed (i don't want it). screenshot HTML5 FireFox

screenshot firefox

  • I had an older Nightly version that worked for me (kind of) but I mistakenly upgraded it. I think it was version 56 or 55. I could not find an older Nightly version to download. For example, in the Mozilla download site, under the nightly dir (or was it trunk?), I downloaded version 56. When I installed it, I saw that it is actually an ordinary Firefox (not Nightly). The reason I use Nightly is because of the "container tab" feature that seems not to be included yet in Firefox. Where can I find the actual older versions of Nightly? – rapt Aug 7 '17 at 7:34
  • Also, I don't think what you suggest is necessary. I can first try to copy my firefox-trunk profile to my older firefox dir. Also, I looks like features like container tabs can be installed on the top of the stable firefox. I will check it out, instead of messing with the nightly stuff. testpilot.firefox.com – rapt Aug 7 '17 at 7:48
  • I updated my answer for the container tabs ;) – Patrice Aug 7 '17 at 8:43
  • The preference thing is a good idea. I don't think they mentioned it when I was looking up something like those container tabs. They only said it is implemented in the nightly version. So I went back to the stable version 54, but the Youtube HTML5 page still shows the same options supported. And same blank window when I try to watch a video on Youtube. Something is missing in Firefox since my hardware supports it as can be seen in Chromium. I also read that just recently Youtube (end of July) Google totally disabled Flash on Youtube. Are you able to see HTML5 videos on Youtube from Firefox 54? – rapt Aug 7 '17 at 19:08
  • P.S. I noticed the container tab on firefox 54 have a minor bug that was not in the nightly 57. When I go to file > new container tab, the colors of the tabs are not shown, only the names. The tab itself has the right color. Oh well. – rapt Aug 7 '17 at 19:13

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