I just used this to migrate from Emby to Jellyfin, works really well. I already have trakt setup on my main account but for my kid nothing goes out to the cloud so their account was all done with watchstate. It was also handy to keep Emby and Jellyfin in sync during the transition.

Thanks this looks great!

This tool is neat for updating watched status live amongst backends AFTER it’s been set up, but have never gotten it to work to bring a new back end in line with an existing one. I moved from Plex to Jellyfin, then again from Jellyfin to Emby and both times it only marked some of my watched content as played on whatever the “new” system is. And not even on a show by show basis either. If you go from Plex where you’ve watched every episode of a season of a show that has 10 episodes, when it exports that status to Jellyfin or Emby, it’ll mark episodes 1,2,6,9, and 10 as played but not the others. It’s remarkably consistent in this behavior and even after scrapping the DB and starting over it always behaves the exact same.