On a desktop (mobile might be missing/reduced sections), the 5 + 4 videos listed under “Recommended Porn” to the right of the video you’re viewing are based on the videos that you’ve watched. My cookies are automatically deleted after every session so I don’t know whether it’s session-based or how far back into your viewing history it uses (probably a lot).
However, the 19 or 20 videos (depending on your zoom) linked below the main video are all based on the characteristics of that video. The videos to the right will change and adapt as you watch more videos but the ones below will usually be the same for each particular video.
As far as I can tell, at its most simplistic, the algorithm mostly uses words from the title plus categories and tags. Important categories are the type of sex, major racial groupings including mixing & matching between partners (eg black man, white woman), age (again including mixing & matching between partners), body type, breast size, cock size, hair colour, country of origin, but I have also noticed that things like glasses, pigtails, sex in cars/public are also identified as well as circ status for the guy (which I don’t think is purely due to country of origin - see below).
More curiously, I have seen videos with (say) a girl in glasses and a bunch of videos featuring girls with glasses underneath but “Glasses” was not listed in any category, tag, nor in the title. Furthermore, I have seen where the physical orientation has been matched - not just POV which is a category/tag - but women giving a kneeling blowjob with her on the right & the guy on the left, or a boobjob with the women all facing the same way, or fucking on a bed but they’re all mid-distance viewed from a static camera on an oblique angle, etc, etc.
So, I think that pornhub is also using image matching. I’m not going to say the bogey word because it gets bandied about a lot these days by people who don’t know what they’re talking about but if imagefap was using image-matching more than 10 years ago, I don’t see why pornhub wouldn’t be doing the same thing on video thumbs. I’m just surprised that xhamster and xvideos don’t appear to be using it since their recommendations are more generic.
