When you share a YouTube video using the share button it adds “si=some_unique_code” to the URL. If you don’t remove that it shows your personal account to anyone who receives it so that they can chat directly with you. For a lot of people this is their real name.
I’ve seen it all over Lemmy so I figured I’d mention it here! You only need the stuff before the question mark in the URL to let others see the video.
This can also be turned off in your YouTube settings under the privacy section. The setting is “channel visibility for shared links”. It will still add the si code for tracking though.
That app seems not as transparent as it could be since it doesnt give any detail on the removed stuff; I recommend URLCheck instead, which is fully transparent about all trackers and even lets you pick which ones to remove at will.