DEUF - Duplicate Entity UUID Fix

Solution for Duplicate Entity UUIDs

Are you familiar with the constant log messages "Keeping entity minecraft:xxxx that already exists with UUID xxxx"? This error occurs particularly often when working with old Minecraft worlds. Despite the bug being known to developers for some time, no official fix has been implemented yet.

The DEUF mod was created specifically to solve this problem. It automatically detects entities with duplicate UUIDs and assigns them new unique identifiers, completely eliminating console and log spam.

Simple Installation and Usage

Installation is extremely simple - just place the mod file in the mods folder. It's important to note that clients don't need to install the mod to connect to the server, making it an ideal solution for multiplayer servers.

After installation, simply continue exploring your world. During the first load, you might notice an increase in messages - this is normal, as the mod reports the UUID changing process. However, in subsequent world reloads or server restarts, the duplicate UUID problem for these entities will completely disappear.

Mod Operation Example

Without the mod:

[17:41:21] [Server thread/WARN] [net.minecraft.world.WorldServer]: Keeping entity minecraft:painting that already exists with UUID bd4f648f-ca0d-4680-9ed5-d28c68356379 
[17:41:21] [Server thread/WARN] [net.minecraft.world.WorldServer]: Keeping entity minecraft:painting that already exists with UUID 1bfcaf96-e93d-4dd8-a402-dc000794acae 
[17:41:21] [Server thread/WARN] [net.minecraft.world.WorldServer]: Keeping entity minecraft:painting that already exists with UUID 2a01ea3a-1ac2-48fa-9731-1399c3f5d256 
[17:41:21] [Server thread/WARN] [net.minecraft.world.WorldServer]: Keeping entity minecraft:painting that already exists with UUID c77765cb-f3fa-42d8-9326-52fa7e176dad

With the mod (first load):

[17:41:21] [Server thread/WARN] [net.minecraft.world.WorldServer]: Keeping entity minecraft:painting that already exists with UUID bd4f648f-ca0d-4680-9ed5-d28c68356379 
[17:41:21] [Server thread/INFO] [uuidfix]: Changing UUID of entity minecraft:painting that already existed from bd4f648f-ca0d-4680-9ed5-d28c68356379 to ae673ae3-2d57-4cf0-b192-87e4dee826d5 
[17:41:21] [Server thread/INFO] [uuidfix]: Changing UUID of entity minecraft:painting that already existed from 1bfcaf96-e93d-4dd8-a402-dc000794acae to b727c571-7fd0-4e98-8bf2-fd63c935dbc5

With the mod (subsequent loads):

Messages are completely absent

Important Warning

Although the mod has passed brief tests and shown stable operation, it's recommended to create a backup of your world before use. This is a standard precaution when working with any modifications that affect save files.