4k video not going entirely full screen on YouTube

[limon11]

When I export a video in FHD and upload it to YouTube, I can play it full screen with no problem but when I export the same video in 4k, even in full screen it doesn't fill up the entire screen. I can see that the same issue in the following video: https://www.youtube.com/watch?v=F4rojV54Rfk

But if you look at other 4k videos on the same YouTube channel (for instance, https://www.youtube.com/watch?v=bm8B8KTAHfg), they do go entirely full screen. Does anyone know if this is something that can be solved by changing my export settings? Any explanation for why the video doesn't fill up the entire screen when I upload a 4k video? I would appreciate any help.

I'm using h.264 4k when exporting and I shot the video in fhd.

[Ann Bens · Accepted solution]

4K is 4069x2160 and is not real 16:9 hence the black bars.

If you want full screen you need to export to UHD which is 3840x2160 and is real 16:9 and will fill the entire screen.

Nowadays, the phrase 4K is often misused, imo.

[limon11]

Thank you for the response. I have tried UHD as it has the same ratio as fhd and it does fill up the entre screen but when I upload it to YouTube, the highest resolution for playback is 1080 p. Do you know in what format or resolution I have to export the video in PremierePro to make the option of 4k (2160p) available for playback on YouTube?

[limon11]

Oh, nevermind. 4k playback is now available! I guess it just hadn't processed the 4k option. Thank you, anyways!