DEUF - Duplicate Entity UUID Fix [NeoForge]
Java mod listed for Minecraft 1.21. Downloads from the MC Java Mods app on Android.
⬇ Download on CurseForgeThe author built this one for Minecraft 1.21.1–1.21.11 on NeoForge. On other versions it may install and then do nothing.
"Keeping entity minecraft:xxxx that already exists with UUID xxxx"
Now that message can occur quite often in case you use an old world. And there is no fix for it currently even though the bug is listed in the bug tracker for some time now. The logs (and server console, in case you have one - like me) also get spammed quite a lot so I thought I would make a mod which fixes those duplicate UUIDs and thus removes the spam.
Simply drag and drop the file into your mods folder. Clients do not need to install the mod to join your server (in case you use it for a server - like I do).
When installed, simply explore your world. Initially the spam will be more than before, since there should be an additional message which tells you that the UUID has been changed. But when reloading the world or restarting the server, that will not occur anymore for that exact entity, which now has a non-duplicate UUID.
Port of CAS_ual_TY's DEUF to NeoForge 1.21.1+ under the MIT license.
- Edition: Minecraft Java
- File type: .jar
- Minecraft versions listed: 1.21.8, 1.21.5, 1.21.4
- How to install: Install the matching mod loader (Forge, Fabric or NeoForge) for your Minecraft version. → Download the .jar. → Put it in the .minecraft/mods folder and launch that loader profile.
- Where to get it: Opens on CurseForge — not every file is mirrored on our own servers.
Install steps are the general flow for this file type — How to install Minecraft Java mods & modpacks walks through it step by step.
- Ships as deuf-26.1-1.0.jar — drop this file into the mods folder
- Download size: 13 KB
- Download link checked 3 Oct 2026 — working
These come from our own check of the pack file, not from the source page.