Can't view full screen youtube videos in Safari 12.


macrumors newbie
Original poster
Feb 13, 2016
Vienna, Austria
Since, yesterday, January 31st 2019, I can't watch full screen youtube videos in Safari. In full screen mode, the videos render on only the left part of the screen. The right part of the screen, and the lower part of the screen are white.

I filed Apple bug 47733671 for this. Please file more bugs at the Apple Bug Tracker and reference this bug number!


I can't reenter full screen mode on youtube videos viewed in Safari after I exited it once.

Steps to Reproduce:
  1. Go to
  2. Click on any video.
  3. Click on the "full screen" button, or press the 'f' key.
  4. Exit full screen mode.
  5. Try to enter full screen mode again, like in step #3.
Expected Results:

I expect the video to be full screen.

Actual Results:

The video is not full screen after step #5. After step #3, the video is full screen, but it appears the video can be set to full screen only once.

Only a small portion of the screen is used. The rest is white. Here is an example of the problem, and here is another example. Note that that is a screenshot of the entire screen. I can see the extra black and white portions.

If I refresh the Safari tab, the behavior persists.

If I create a new Safari window, the behavior resets, and I can view full screen youtube videos, but again, only once.

I first noticed this problem yesterday, on January 31st 2019.

Any other video site (apart from youtube) works fine. Also Chrome and Firefox work fine.


The version of macOS doesn't seem to matter, I tested macOS 10.13.6 (17G65), macOS 10.14.2 (18C54) and macOS 10.14.3 (18D42).

The version of Safari matters:

Not working:
  • Safari Version 12.0 (13606.2.11)
  • Safari Version 12.0.2 (14606.3.4)
  • Safari Version 12.0.3 (14606.4.5)
  • Safari Beta Version 12.1 (13607.1.22.1)
  • Safari Technology Preview Release 65 (Safari 12.1, WebKit 13607.1.5.2)
  • Safari Technology Preview Release 74 (Safari 12.2, WebKit 14608.1.1.1)
  • Safari Version 11.1.2 (13605.3.8)

This behavior was reproduced on multiple computers, desktop and laptops.

Additional information:

It appears the smaller image I see instead of full screen has the same size as the original Safari window. That got me thinking, so I enlarged the Safari window to test this hypothesis. It appears that if the Safari window is large enough, the problem disappears.

There's a problem even without full screen though. It appears that sometimes youtube doesn't resize. This correlates 1:1 to the full screen problem. If youtube resizes, full screen works, if youtube doesn't resize, full screen mode fails.

It appears that on my iMac 2834 pixels wide is already too small. This value depends on the display used. On laptops, it's lower.

Another way to see the problem is this. IFF the Safari window is less wide than some number of pixels, after you have entered full screen and then exited it, youtube doesn't resize anymore as you change the dimensions of the Safari window.

On older Safari versions, where youtube works fine, this is how it works:
  1. I click on full screen.
  2. The page becomes full screen, but the rendering is the same as when it was in window mode.
  3. After a very brief moment, the page re-renders, this time with the video occupying the entire screen.
It appears that on Safari version which do not work, step #3 doesn't happen. Window is stuck at step #2.

More reports of the same bug:
Please file more bugs at the Apple Bug Tracker and reference the bug number 47733671! This is how Apple prioritizes fixes, by the number of bug duplicates!
[doublepost=1549039112][/doublepost]This is how it looks like when refreshing while in full screen mode.
Last edited:


macrumors member
Jan 29, 2019
Liverpool, UK.
This seems like a simple, but dumb approach, but I would suggest installing an alternate web browser (namely chrome or FireFox), setting them up as your default browser and then trying to reload safari.

If this has not worked, make Safari your default broswer and repeat again - works for me.

Alternatively, either an SMC or NVRAM reset should do the job, heres some links to help you: (SMC reset) (NVRAM reset)

Hope this helps.


macrumors 65816
Jan 26, 2008
Poznan, Poland
SMC and NVRAM have nothing to do with Safari. I worked around this problem by setting "Show scrollbars" to "when scrolling", but there were users who tried this and it didn't work for them.