Protocol version

A protocol version number (PVN) or network version is an integer used to check for incompatibilities between the player's client and the server they are trying to connect to.[1][2]

Client and server versions with the same protocol version are compatible with each other. For example, a client running Java Edition 1.8.9 can connect to a server running Java Edition 1.8, as both have a protocol version of 47.

Upon attempting to join a multiplayer server, the game checks if the client has a protocol version newer or older than the selected server; if it does, the game then alerts the player that their client (or the server) is outdated.