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Managing UUID Fixer Policies and Overriding Player UUIDs in LAN World Plug-n-Play

guide

The UUID Fixer controls how player identities are handled when someone joins your LAN server, and it is the key tool for migrating a world away from online-mode authentication. This guide covers its policies, per-player overrides, and how to move a world from online mode while keeping inventories intact.

Understanding the Three Policy Types

Each policy decides what UUID a joining player receives. There are three valid values:

  • A policy of online requires a genuine Microsoft/Mojang account and assigns that account's authentic UUID.
  • A policy of offline lets anyone join, including players without a verified account.
  • A specific UUID can be supplied directly as the policy, forcing that exact identity onto the player.

If you enter anything else, the mod rejects it and reports that the policy is invalid, reminding you it must be online, offline, or a properly formed UUID.

The Default Policy

The UUID Fixer has a default policy that applies to players who have no individual rule. You can view the current default, and you can change it. When a change succeeds, the mod confirms the new setting. This default is what most players will fall under, so choose it carefully — for example, set it to offline if you want open access, or to online if you want verified accounts only.

Per-Player Overrides

Beyond the default, you can maintain a policy list holding individual rules. To see how many rules currently exist, check the list; the mod tells you the count. If no rules have been added, it reports that the list is empty.

For any named player you can:

  • Assign a policy, which the mod confirms by naming the player and the policy applied.
  • Override that player's UUID, replacing their existing identity with a new one — the mod confirms both the player and the replacement value.
  • Remove a player from the list, which the mod acknowledges once done.

If you try to remove or modify someone who was never added, the mod warns you that the player is not present in the policy list.

Migrating From Online Mode

The Disable + UUID Fixer mode is built for exactly this situation. It opens the server to everyone, including offline players, but anyone who does hold a valid Microsoft/Mojang account will still be given their true, unique UUID. Because identities are preserved this way, existing inventories carry over. Use this mode when you are moving a world off online-mode authentication and want player data to stay attached to the right people.

Several nearby options affect who can join and how the server behaves:

  • AllPlayersCheats grants joining players permission to run administrative commands. As an alternative, the /op command can promote someone to operator.
  • The whitelist option, once turned on, restricts entry to listed players only; the /whitelist command adds them.
  • The account-verification setting decides whether login details are checked against the Mojang database — either admitting only valid Microsoft/Mojang accounts, or allowing anyone including offline players.
  • UseUPnP handles port forwarding automatically and announces the server on the LAN so nearby players can spot it directly.
  • The public IP can be retrieved and copied for sharing, though NAT and similar factors may still block direct connections.
  • removePlayerReportingButton swaps out the player reporting button.
  • lanServerOptions opens LAN server settings, and backToVanillaScreen returns you to the standard screen.

Port forwarding attempts report their outcome: success, a port already claimed by another UPnP service (change the port), UPnP disabled on the router, an unknown mapping error, or a general failure. Note that turning off PvP also stops you from harming yourself with your own projectiles.