I had been using firefox 49 on Ubuntu 14.04, 64-bit, with the user agent solution found here, and all was well: Now that I have Firefox 49 or higher, how do I watch Netflix?

Then firefox 50 came along and now I get this message at the top of the browser window:

"libavcodec may be vulnerable or is not supported and should be updated to play video"

And netflix tells me:

"Whoops, something went wrong... Netflix Video Player Unavailable We're having trouble playing Netflix on your browser. Please make sure you are on an official version of Chrome.

Error Code: M7355-1204"

I have tried searching for the libvacodec error and for firefox 50 + netflix. Anyone have a solution to this?

  • 2
    See here for the fix: superuser.com/questions/1137029/… Nov 20, 2016 at 14:13
  • I really gave up netflix on firefox. I have chrome just for that. Nov 22, 2016 at 16:04
  • Vitor Abella, its working well for me across many machines. All i needed was the user agent fix. see below
    – kosf
    Jan 2, 2017 at 21:27

2 Answers 2


Ubuntu Modifications 3.2 is causing the problem! If you are using Ubuntu (any flavor) and are using Firefox as a search engine go into Add-ons manager then into Extensions and disable or remove Ubuntu Modifications 3.2! Restart Firefox ------ Linux Is Great :-)

  • Hi, good news, the problem seems to have been fixed so no need to disable ubuntu modifications. thanks though.
    – kosf
    Jan 2, 2017 at 19:10

Update + solution: the problem was fixed so SKIP STEP 1.

if you want to just get netflix running by changing the User Agent of the browser follow steps 2-3

1) Update Libvacodec https://superuser.com/questions/1137029/libavcodec-may-be-vulnerable-message-in-firefox

2) Install UAControl* (seems like best user agent switcher because you can set the user agent for just 1 website like www.netflix.com) https://addons.mozilla.org/en-us/firefox/addon/uacontrol/?src=search

3) Open "UAcontrol options..." -> click "add site" -> for "site:" put www.netflix.com

-> paste this code in "custom" text box:

Linux / Chrome 53: Mozilla/5.0 (X11; Ubuntu; Linux x86_64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/53.0.2785.34 Safari/537.36

*Because netflix are mean and don't care about ubuntu users and force us to fool them into thinking we are using a different operating system/browser combo.

  • 1
    Thanks to users Organic Marble and GizmoChicken over here for the user agent code line: askubuntu.com/a/828305/609155
    – kosf
    Dec 6, 2016 at 0:05
  • Can anyone confirm if this is working on 32-bit 14.04?
    – kosf
    Jan 2, 2017 at 19:24
  • It worked on 32 bit in FF 49. Seems to not work in 50. Jan 17, 2017 at 2:06

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