Since this week's security update, YouTube will not fullscreen in Safari. Help?

Safari/Preferences/Advanced - enable the Develop menu, then go there and Empty Caches. Quit/reopen Safari and test. Then try Safari/History/Show History and delete all history items. Quit/reopen Safari and test. You can also try try Safari/Clear History…. The down side is it clears all cookies.Doing this may cause some sites to no longer recognize your computer as one that has visited the web site. Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Select Library./Caches/com.apple.Safari/Caches.db and move it to the trash.

Go to Safari Preferences/Extensions and turn all extensions off. Test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.

Safari Corruption See post by Linc Davis

You are welcome. Will other websites open in Full Screen? Will it open in Full Screen, but not play correctly? If that is the case, try pausing the video and then start playing it again.

Send Apple feedback. They won't answer, but at least will know there is a problem. If enough people send feedback, it may get the problem solved sooner.

Feedback

Or you can use your Apple ID to register with this site and go the Apple BugReporter. Supposedly you will get an answer if you submit feedback.

Feedback via Apple Developer

Joe and Eric.

I was checking into this issue and can duplicate it on My MBP which I just updated to 10.11.2 yesterday. Looks like it could be a YouTube problem because I tried the installation videos on the OWC web site and they do fine in full-screen HD mode. I also tried the web sites for two TV channels that play old episodes of their programming. That works fine, also.

In YouTube, stopping and restarting as Eric suggests restores full screen.

I have only one extension (ASCPowerTools) and turning it on or off did not affect this YouTube behavior. I run no ad blockers or anti-virus software.

EDIT: I moved back to my iMac running 10.10.5 and Safari 8 and the Youtube problem is there too. Other sites are fine. So it is NOT this week's security update.

Offered for your consideration.

Allan

There's another security update 2015-006 and an iTunes update - the security update should fix your issue.

Just applied the 006 security update and iTunes 12.3.2 to the iMac with OS10.10 and Safari 8. No change.

The MacBook Pro with 10.11 already had iTunes 12.3.2 but the 006 security update is not offered for that computer. Will check again later.

I still think YouTube has a problem as all other video sites that I visit work fine in full screen on both Macs.

Try pausing the video and then start playing it again.

Try pausing the video and then start playing it again.

This workaround works (y)

I have the solution for this error with Safari and Youtube. It's very easy, after all. Follow these steps:

1. Download ADWARE MEDIC (http://www.adwaremedic.com/). It's the ONLY APPLICATION authorized by Apple.

2. Install, open and click on "Scan".

3. Remove all malware.

4. Close the application.

5. Open "Finder", hold down the Alt button and click on "Go to" > "Library".

6. Look for the "Preferences " folder and duplicate it in the same place.

7. Now, you must have "Preferences" and "Preferences copy". If you have, delete "Preferences".

8. Restart your computer.

9. Check Youtube.

😉

Joe

Are you running Kaspersky?