Player files contain any player-related data on a server. This includes inventories, achievements, location, etc.
Sometimes it's required to delete someone's player file. Usually if a player got bugged or if someone did some experiments with a player like teleporting him to invalid coordinates.
Deleting someone's player file causes any data related to the player to be reset.
1. Find out the UUID of the player
A UUID is a longer string that consists of several random letters and numbers. This UUID is used to identify each player on your server.
If you already know the UUID of the player whose playerdata you want to delete, you can skip this step.
Ask the player whose file you want to remove to join the server. A message will appear your server console that a player tried to join the server. This message contains the user's username and UUID.
Note down the UUID of the player.
2. Delete the player file
Navigate to the "playerdata" directory.
This folder now contains all playerdata. Each player on your server has their own file. Find the file that is named after the UUID of the player whose player file you want to delete, and click the trashcan icon to remove it.