There's a UI tweak I'd like to make before doing anything with the data. I was actually working on this last week so it's close to being completed. Right now the "watch trailer" button only shows for trailers which is why this happens more often than it should (I've even done it.) So I'd like to fix the experience around that first and then we can look at cleaning up the data.

Before doing something it could be worth checking some individual cases. We (some of the mods) kind of decided in the past that any teaser trailer below 90 seconds should be added as a teaser, but above 90 seconds should be added as a trailer. For me, personally, a teaser Trailer is not a teaser but a proper trailer, but I know some others may disagree about that. So that's why, in the end, the compromise was the 90 second split.

With that background I assume that many of the Teaser Trailers are correctly placed as trailers based on the previous decision.

I am currently using the YouTube API v3 to check which trailers have been removed, which have been blocked due to copyright issues and which are region blocked in various areas.

Although a pipe dream, it would be good if TMDB had a cron job which did the same and removed accordingly.

You can also get trailer lengths from it.

Ya, I already use the YouTube API to validate entries and get things like length. I ran every record through it earlier in the year and removed all content that was no longer available.

It’s not something I think we need to run very often but it could easily be ran a few times a year.

A agree it only needs to be done X amount per year. Quarterly or Monthly.

Of the 64740 trailers that I checked, which were grabbed on the 1st of September:

873 are region blocked in some countries.
534 are not accessible due to copyright infringement.
739 are dead.