Plex has added a new feature that can sync watch state and user ratings between multiple Plex servers. So, if you have multiple Plex servers with the same content, the content will be marked as watched (or unwatched) on all of them when the state of one server changes. This also means that content you watch on a friend’s server will also be marked as watched on your own server, if you both have the same content. The same syncing occurs for user star ratings for content.
In addition to syncing between your private libraries and/or those of your friends, this syncing will also occur when content in Plex’s own library of free movies and shows is watched or if you mark content in the Discovery tab as watched. So, for example, if you happen to watch one of the free movies that Plex offers and then later add it to your own private library, the movie will correctly be marked as watched. It’s worth noting that this feature does not sync the current watch progressive of any content, regardless of where it is.
The new feature is optional and you should see a prompt to enable it or leave it off the next time you log into your Plex dashboard. You can also find the setting under Settings > Account > Sync My Watch State and Ratings. You must be running v1.27.2 or higher of the Plex Media Server and you must be using Plex’s default metadata agents for the feature to be available and work properly. Plex says you may need to restart your Plex server for the change to take effect and some watch state and rating changes can take up to 30 minutes to appear across all servers.