Modern iPhones capture full hi-def videos with 1920x1080 resolution. When I download the MOV file to my computer and then upload it to YouTube, it only shows as 360p resolution.
How do you upload iPhone videos to YouTube keeping their HD resolution?
hmm... turns out YouTube shows HD options for the video only some time after the video is uploaded. My guess would be that YouTube continues processing the video in the background and exposes the various resolutions only when they are done processing.
So the answer is: just upload your HD videos, it'll retain the resolution after a while