Youtube full screen mode only shows 1/4 of the video

Hello everyone,

I had the same issue too until I went to the Apple Store wherein they checked out my settings.

I have find a solution to this issue!
If you have an external wireless mouse or USB, this is something that might cause the issue. To fix the issue, follow the following steps.
Optional:
Restart your MacBook.
Steps:
Go to System Preferences ---> General ------> Show Scroll bars -------> Change to "When scrolling."
Go to YouTube on Safari and the problem should be fixed now! 🙂

Kevin Nguyen and Apple Support

Same problem started happening today with my MacBook Pro 15 with M370X.

Pausing the video in fullscreen, and then resuming it will fix it, but you have to do this for every new video you watch. Extremely annoying! (pressing spacebar to pause saves some time)

I have upgraded form Yosemite, and I was wondering if others have as well. I will try to do a full backup overnight, format the HD, and reinstall the OS.

I will let you know if this fixes the problem.

I too have had the same problem. I recently upgraded to OS X El Capitan 10.11.2 when the problem started. However, I also upgraded my little Macbook and it does NOT have the problem.

The split or half screen only occurs on my MacMini/Thunderbolt display. Clicking several times on the screen opens it to full screen...pause, click to start...opens to full screen.

However, I used Firefox as an alternative to Safari, and it does not occur on Firefox.

Any thoughts or suggestions. Thanks.

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.

😉

Greetings!

I have the same problem. Anyone please? 😢

Same problem here, i always have to change the resolution of the video, but it's annoying

Try another browser as a test.

Firefox

Chrome works great, so its a safari only problem. I do preferSafari however.

I'm having this same issue. It just started today. Very annoying. As others stated, it seems to only be a problem in Safari. Chrome works fine but I prefer using Safari.

Same issue here...

Same issue too! It seems many people have this problem , it's so annoying.

Experiencing the very same issue. Only started happening after the upgrade to the official release of El Capitan 10.11.2 a few days ago.