Mozilla FireFox is a web-browser developed and published by Mozilla.
Vine videos (HTML5 videos) don't play
The issue presents itself with a static image appearing instead of a video playing. Vine videos especially have this problem. The problem appears to be at the fault of FireFox's built-in mp4 media player.
Disable the built-in mp4 media player:
- Open a new tab
- Type in about:config in the address bar
- If confronted by a page saying "This might void your warranty!" click the "I'll be careful, I promise!" button
- In the search bar at the top of the page copy and paste media.windows-media-foundation.enabled
- Double-click on the media.windows-media-foundation.enabled string to disable it
- Restart FireFox and try loading a Vine or HTML5 video