New issue, just started after using MacBook Pro for a couple weeks. YouTube vids will go black during video playback - only the video square, and can still hear audio. Nothing on the laptop has been changed recently. Everything else seems to be working fine. It's very mysterious.
MacBook Pro with Retina display, OS X Yosemite (10.10.3)
Found this workaround you might try:
Solution that worked for me til fix of the Safari bug: Open Safari Preferences >extended, there -mark "show developer Menu"
> then choose Develop > User Agent > Chrome Mac or Firefox Mac.
via: Yosemite 10.10.1 causing Safari not to play YouTube videos...
I recently purchased a new Macbook Pro less than one week ago; I am experiencing the same issue. I've tried everything I could think of. Only solution I've found is to use FireFox instead of Safari when I watch a youtube video.
Also tried Paxman999 suggestion and youtube videos still go black during playback.
I think I got things working by adjusting the tweak above. I'm running Yosemite 10.10.3 and the latest version of Safari 8 and Flash player (make sure those are up-to-date-first).
Try these steps:
1. Safari > Preferences > Advanced > Tick 'Show Develop menu in menu bar'.
2. Develop > User Agent > Safari 7.1.5
I couldn't get it working with the Google Chrome for Mac option, but the downgraded version of Safari seems to be doing it... tells me that there's something funky with the last Safari update.
This helped one guy earlier today:
Open Safari - Clear History and Website Data.
More info here: Youtube video turns into a black screen randomly
Hope this will help you as well!
YouTube vids go black during video on new MacBook Pro 15
