The .7z extension indicates the folder has been compressed using 7-Zip , a popular tool for reducing file size for storage or transfer.
Files are named using the player's UUID (Unique Universal Identifier) rather than their username. PlayerData.7z
In the context of a Paper server, PlayerData is a folder that stores individual files for every player who has joined the world. PlayerData.7z
The phrase most likely refers to a compressed backup of player data from a Paper (PaperMC) Minecraft server. 📦 What is PlayerData.7z? PlayerData.7z
These files (ending in .dat ) contain inventory, health, experience, and coordinates.