So I'm sure this question has been asked like a thousand times. But I wasn't able to find a good answer to it. I'm currently working on a plugin that converts saves of an old plugin (not coded by me) to a new format (coded by me). The old plugin saved files in the format "playername.properties" and since UUIDs have been introduced, I'll need "uuid.properties". I'd like to be able to convert all files at once without having people playing on the server, because the plugin might break when theres 50% UUID and 50% Playername. So I need to get the UUIDs of offline players without having any information about them but the name I've seen them the last time with. I've read threads like "Getting Offline Player UUID" on the spigot forums, but they link to libraries and threads that are not accessable anymore. I know sites where I enter the player's current name and it outputs me the UUID, so it should be possible to access that through my plugin, right? And since I'm hopefully not the only one with this need, there should already be a UUID Fetching class that works with offline players, huh? I'd really appreciate some hints.