All youtube videos stopped playing suddenly today

I've tested a few computers, and I can confirm that it is NOT a Flash issue.

This is definitely a problem with the YouTube HTML5 player, not Safari. I've tested this on my rMBP 13", and I tested some demo units at the local Apple Store. My unit has OS X 10.10.1, while theirs were still running 10.10. All have the same issue: The HTML5 player is refusing to load anything, even ad-free content.

This is a technical issue on the part of Google. You're gonna have to wait it out until Google fixes this. In the meantime, Chrome is a good-enough workaround.

I just posted a similar thread earlier over here: https://discussions.apple.com/thread/6684406

See if this video plays ok - it seems to work ok for me (after initially displaying an error) : http://youtu.be/MM6XG1DOwrs

This worked for me. Thanks, Dominic.

I don't use Flash but HTML5 so this did nothing for me, however if you enable the developer menu in Safari and then select user agent as Chrome, everything works fine.

It'll need to be selected every time you launch Safari, but it'll do until the issue is fixed.

Same issue, youtube videos don't play on safari after updating, or at least just today. Audio clipping/shriek for part of a second, like others.

Same here... Looks like a Google problem... Just started today. Oh well, will be using Chrome for anything Youtube until fixed.

It does NOT fix the problem.

Wait until you hear from Google.

Try deleting YouTube website data.

Safari > Preferences > Privacy > Cookies and other website data:

Press the”Details” button. A sheet will drop down.

Enter YouTube in the search box at the top right corner.

Highlight the YouTube entries that show up.

Click the “Remove” button at the bottom, then “Done”.

When I try to play HTML 5 video, "Learn more" leads to this message.

https://support.google.com/youtube/answer/3037019?p=player_error1&rd=1

Already did it several times, uninstalled flash player, repaired permissions, rebooted my Mac, installed flash player. Nothing helps. Switched back to Firefox (used to use it for years, but always had a dream to use Safari some day). It seems that guys from Apple are not able to create any stable version of Safari... 😕

Im having exactly the same problem, its especially annoying considering Youtube is the main thing I use safari for. Nothing been released from Apple about this issue yet?

Now its working again! no idea what had happen, but I can now use Safari-Youtube without issues
PS: sad no reply has been written from Apple support service so far no info!

I've sent Feedback to Apple along with a link to the thread I created on this topic (https://discussions.apple.com/thread/6684406)

I'm sure Apple employees use Safari to watch Youtube videos so I'm sure they are aware of the issue (you'd think)...

Unfortunately nothing works... only if you use user agent as safari 7.1 or anything else but 8.0