Joining kicks another player / only one player can be online at a time — why?
If a new player joining kicks whoever's already online — so only one person can be on at a time — you're seeing a UUID or username collision. This is the tell-tale sign of duplicate accounts, and it's most common on offline-mode (cracked) servers.
Why this happens
Minecraft identifies each player by a unique UUID. When two clients present the same UUID or name, the server treats the newcomer as the existing player and boots the first one. On cracked servers, two people with the same username collide directly. On premium servers it can stem from a proxy forwarding the same UUID.
How to fix it
- Ensure everyone uses unique usernames. Two identical names collide on offline-mode servers.
- On cracked/offline servers, add an auth plugin such as AuthMe so accounts are registered and kept distinct.
- On premium (online-mode) servers, check for a proxy misconfiguration — a BungeeCord/Velocity setup forwarding the same UUID will cause this. Confirm IP/UUID forwarding is set up correctly.
Tip: Online mode (
online-mode=true) gives every premium account a genuine unique UUID from Mojang, which avoids collisions entirely when your players own the game.
Frequently asked questions
Why does this only happen on my cracked server? Without Mojang authentication, the server can't guarantee unique identities, so matching names clash. An auth plugin fixes it.
We all have different names and it still happens. On a premium server behind a proxy, suspect UUID forwarding. Review your BungeeCord/Velocity and backend online-mode settings.
Is AuthMe required? Only for offline-mode servers, where it's the standard way to keep accounts separate and secure.