Test upload on 4K footage. Previous uploads from FCPX downsizes footage to 1080p. The same happened when I tried to edit a 4K resolution video using YouTube Editor. This footage has been uploaded directly with no editing/post production.
No turtles were harmed during the filming of this experiment!!
![](https://i.ytimg.com/vi/ukQXhqLHDT0/maxresdefault.jpg)