@jjohnson84uk-0 there is a technique called steganography, which consists of watermarking the file image noise, that is, slightly alterating the value of specific pixels, so it is completely spotless and only the person who encoded it has the password to decode it.
For images it is a very simple process, but for videos it's super tricky, complex and expensive.
Chances are that adult sites use stenography for pictures, but for videos the most likely way that they use to track the user ID would be video metadata and file names.
So if you decide to share, I'd advise you to skip the pictures, only share the videos. And before doing that, use ExifTool to get rid of all metadata, and rename every file.