warning

This server is issuing offline-mode identities

Q: What does "UUID of player Steve is 8667ba71-b85a-3004-af54-457a9734eed7" mean?

This server is issuing offline-mode identities. The UUIDs handed out at login are version 3, generated from the username instead of issued by Mojang. That means online-mode=false, or a proxy in front that is not forwarding real identities. Two consequences, both worse than they look. Anyone can join under any name, including your admins, because nothing checks the account. And the UUID is the player identity: flip online-mode back to true and every inventory, home, claim and permission tied to the old UUID looks lost, because the player is now a different person to the server. Set online-mode=true in server.properties before the world has history, or configure proper forwarding if a proxy is meant to be handling authentication.

Q: How do I fix "UUID of player Steve is 8667ba71-b85a-3004-af54-457a9734eed7"?

1. Decide which mode you mean to run: If nobody set this on purpose, it should be true. Set online-mode=true in server.properties and restart before the world has any history worth keeping. 2. If a proxy fronts this server, fix the forwarding: Behind BungeeCord or Velocity the backend runs offline by design and the proxy authenticates. But the proxy must forward the real UUID: bungeecord: true in Paper's spigot.yml for BungeeCord, or velocity-support with the shared secret for Velocity. Without that the backend generates offline UUIDs and you get the wipe on the day someone fixes it. 3. Lock the backend down: A backend behind a proxy has to be unreachable except from the proxy, or the offline mode is a public door. Firewall the port, or bind the backend to a private interface. 4. If you must switch modes with history, migrate the data: Plugins exist to rewrite player data from offline UUIDs to online ones. Back up first, run one, and check a couple of players before opening the server.

What it looks like in your log

UUID of player Steve is 8667ba71-b85a-3004-af54-457a9734eed7

What causes it

The UUIDs handed out at login are version 3, generated from the username instead of issued by Mojang. That means online-mode=false, or a proxy in front that is not forwarding real identities.

How to fix it

Two consequences, both worse than they look. Anyone can join under any name, including your admins, because nothing checks the account. And the UUID is the player identity: flip online-mode back to true and every inventory, home, claim and permission tied to the old UUID looks lost, because the player is now a different person to the server. Set online-mode=true in server.properties before the world has history, or configure proper forwarding if a proxy is meant to be handling authentication.

Why it happens

Every player has a UUID. With online-mode=true it is issued by Mojang, tied to the account and the same on every server in the world. With online-mode=false the server generates one from the username instead, and that is a version 3 UUID: the third group starts with a 3. Roastd saw one at login, which means either online-mode is off or a proxy in front is not forwarding real identities.

Two consequences. Nothing checks the account, so anyone can join as anyone, including your operators. And the UUID is the identity everything is stored against: inventories, ender chests, homes, claims, permissions, economy balances. Flip online-mode back to true later and every player becomes a stranger to the server, with an empty inventory, because their UUID changed. It looks like a wipe. Nothing was deleted.

Fix it step by step

1Decide which mode you mean to runIf nobody set this on purpose, it should be true. Set online-mode=true in server.properties and restart before the world has any history worth keeping.
2If a proxy fronts this server, fix the forwardingBehind BungeeCord or Velocity the backend runs offline by design and the proxy authenticates. But the proxy must forward the real UUID: bungeecord: true in Paper's spigot.yml for BungeeCord, or velocity-support with the shared secret for Velocity. Without that the backend generates offline UUIDs and you get the wipe on the day someone fixes it.
3Lock the backend downA backend behind a proxy has to be unreachable except from the proxy, or the offline mode is a public door. Firewall the port, or bind the backend to a private interface.
4If you must switch modes with history, migrate the dataPlugins exist to rewrite player data from offline UUIDs to online ones. Back up first, run one, and check a couple of players before opening the server.

If that didn't work

If online-mode is true and the log still shows version-3 UUIDs, the login is not reaching Mojang: a proxy is in front of you that you did not know about, or a plugin is faking the session.

Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.

Check your own log