How to Play Multiplayer Minecraft LAN Games with a Single Minecraft Account
You can have multiple players join a local LAN game using the same account if you modify their display names.
If you have ever tried to use the same Minecraft in the same LAN game you have seen this screen.
However we were still able to make this work on Minecraft version 1.12.2 Java Edition on the Mac (should also work on Windows just change the paths).
- Edit this file ~/Library/Application Support/minecraft/launcher_profiles.json and change the displayName to another name.
- Edit this file ~/Library/Application Support/minecraft/usercache.json
- Edit this file ~/Library/Application Support/minecraft/usernamecache.json
- Launch Minecraft and Start a Game
- Open to LAN
- Repeat steps 1-3 above on the other computers using the same account and they should be able to to join now.
If you are using a local Minecraft Server you will need to set to 'offline' so it doesn't check usernames.