I've noticed a difference in how Facebook handles video URLs and was hoping someone could clarify this for me.

When I access a video using a URL that includes the username and video ID, it works as expected and directly shows the video.

However, when I try a similar URL with a different video ID, Facebook automatically redirects me to a different format: https://www.facebook.com/watch/?v=video_id.

I’m curious about the following:

What causes Facebook to redirect certain video URLs to the watch/?v= format? Is this behavior related to video privacy settings, URL standardization, or some other factor? Are there any official guidelines or documentation explaining when and why these redirects happen?