Firefox on macOS – Fix YouTube Playback Issues

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I use Firefox as default browser on my Mac. For some reason I can't play Youtube videos anymore. Facebook videos work, and Youtube videos play fine in Safari. If I restart with all addons disabled, it works again. Then if I enable addons one by one, it works up til a certain moment. Then I disable the last addon again, but no luck. Then I disable all addons manually, and still no luck.

What happens is I see a black screen with "static". See the image:

Youtube Static

So I'm a bit lost here. What is the best way to solve this? How can I get this working again? Below the list of the addons I have installed.

  • Adblock Plus
  • Better privacy
  • Calomel SSL Validation
  • Date Picker / Calendar
  • DNS cache
  • Downthemall
  • Empty cache button
  • Flash and video download
  • HTTP fox
  • HTTPS Everywhere
  • Lucifox
  • Mailvelope
  • Master Password +
  • PWgen
  • QR Code image generator
  • Quickfox notes
  • Quick passwords
  • Saved password editor
  • Soundcloud Downloader
  • Tab mix plus

Best Answer

I had this problem for a long time, and I figured it out the hard way.

I encountered this problem whenever I'm on youtube with SSL enabled, and there was no issue while using an http only connection. And it seems flash plugin will establish a connection on its own to stream the videos. The flash client always throws an error when some special cipher suites used in the browser SSL configuration are disabled (RC4/SHA, RC4/MD5) in your browser. The RC4 cipher suites are weak and some add-ons disable them by default for security reasons.

From your add-ons list you have HTTPS everywhere (which would default to https youtube) and Calomel SSL validation (which can disable RC4 cipher suites). It is no fault of the add-ons that video breaks, and it is good to disable RC4. What I'm not sure is to put the blame on a crappy flash client or a youtube stream server that cannot handle modern cipher suites.

In short : go to about:config, search for security.ssl3. and find out the entries for rsa_rc4_128_sha/rsa_rc4_128_md5 and set them to true. Reload youtube, and you are good to go. Most likely Calomel will reset those after a restart. But I think there are options to allow all cipher suites in calomel preferences.

EDIT : The reason you saw the problem even after disabling the add-ons is that calomel might not reset the cipher suite settings after removing.

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