Make sure you are not blocking content.

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop also see https://blog.mozilla.org/security/2021/03/23/introducing-smartblock/

https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection

Diagnose Firefox issues using Troubleshoot(Safe) Mode {web link}

A small dialog should appear. Click Start In Troubleshoot(Safe) Mode (not Refresh). Is the problem still there?

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}

I had done all of these things previously. Also turned off tracking protection, tried safe mode, disabled all plug-ins, etc. This only started a week ago. Twitter never plays the video. YouTube take several minutes to load anything. Also Vimeo. But it's not my computer because Chrome plays everything just fine and video files play fine outside of Firefox. Interestingly, streaming services like Netflix play fine in Firefox. Quite puzzled.

Hii burtco, follow this support link [https://support.mozilla.org/en-US/kb/fix-video-audio-problems-firefox-win...] Thanks reagards -Arman

Thanks to Fred and Arman, but none of these solutions address the problem. As I wrote, video play fine outside of Firefox, including in Chrome (Twitter and YouTube, etc.). I'm a video producer and post clips on Twitter regularly, so I'm pretty aware of the various codecs, etc. My problem started around November 5, which is just one day after Firefox 94.0.1 was released & my browser updated. I can't help but suspect a problem with this newest release, but I'm puzzled as to why I haven't seen others with the same problem. Again, for years, I've had absolutely no problem playing videos from any website via Firefox until just last week. Hope this helps.

Does it make a difference if you "allow audio and video" for those websites ?

• https://support.mozilla.org/en-US/kb/block-autoplay

You can check the Web Console for for possible media related messages.

• https://developer.mozilla.org/en-US/docs/Tools/Web_Console

Thanks again to cor-el, but still no luck. Autoplay isn't a problem here because when a video appears, I click on the play button and nothing happens. Again, I have NEVER had a problem viewing embedded videos on Firefox until a week ago. I am pretty sure it's a problem in the latest upgrade. Is there a way to revert to an earlier version??

Before you delete anything, a few more things to try.

Use these links to create a new profile. Use this new profile as is. Is the problem still there?

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Type about:profiles<enter> in the address bar.

This whole situation is extremely frustrating. Is there anyway someone from Mozilla can comment on this? As I've said several times, this whole embedded video problem (not playing or taking 30-45 minutes to start on Twitter, YouTube, Vimeo, FaceBook) only started with the latest Firefox update. I've used Firefox for years and never had this problem. If this can't be solved, I will very reluctantly have to move to Chrome ASAP, since video is a major part of my work.