
Modrinth · Minecraft mod
Unsafe World Random Access Detector
This is a mod that detects unsafe off-thread world random access, helping to find causes of "Accessing LegacyRandomSource from multiple threads" crash.
Quick answer
Which Unsafe World Random Access Detector release should I use?
Unsafe World Random Access Detector 1.2.0 targets 26.1-rc-3, 26.1, 26.1.1 with Fabric. Installation on the client is optional. Installation on the dedicated server is optional. No extra mods listed for this file.
Where it goes
Is Unsafe World Random Access Detector required on the client, server, or both?
Installation on the client is optional. Installation on the dedicated server is optional.
The source marks this as usable on both the client and server.
What else does Unsafe World Random Access Detector 1.2.0 need?
1.2.0. Change the file and its required mods may change too.
This file does not list any required mods. Do not add a library just because a different file uses it.
This file does not list any required or optional mods.
Before you install it
Add Unsafe World Random Access Detector without breaking your instance.
Built for Unsafe World Random Access Detector 1.2.0. Pick another file and the loader, install side or required mods may change.
- 01
Stick to this file
Use 1.2.0. It targets 26.1-rc-3, 26.1, 26.1.1 with Fabric; another release may have different loader, side or dependency requirements.
- 02
Bring the mods it needs
This file does not list any required mods. Do not add a library just because a different file uses it.
- 03
Put it on the correct side
Installation on the client is optional. Installation on the dedicated server is optional.
- 04
Pick the file you checked
Use the “Get this file” button beside 1.2.0. It opens that exact file at the source.
About this project
What does Unsafe World Random Access Detector add?
Unsafe World Random Access Detector
This is a mod that detects unsafe off-thread world random access,
helping to find causes of "Accessing LegacyRandomSource from multiple threads" crash.
This is useful for finding the cause of mysterious crashes with Accessing LegacyRandomSource from multiple threads.
This is not a fix for the issue, but it will help you find the cause of the issue.

Note: If you are already using C2ME, this mod is not needed (but won't crash if used together anyway).
Project description from Modrinth.
Pick your setup
Unsafe World Random Access Detector by Minecraft version and loader
Choose the version and loader you play, then open the matching release.
26.1.2
1 loader build26.1.1
1 loader build26.1-rc-3
1 loader build26.1
1 loader build1.21.11
1 loader build1.21.10
1 loader build1.21.9
1 loader build1.21.8
1 loader build1.21.7
1 loader build1.21.6
1 loader build1.21.5
2 loader buildsShowing the newest 12 of 29 game versions. Older files are in the list below.
Check the dependencies, then try the file in a copied instance before changing a world you care about.
Recent files
Unsafe World Random Access Detector versions and loaders
1.2.0
unsafe-world-random-access-detector-1.2.0.jar
24 Mar 2026
1.1.3+neoforge
unsafe-world-random-access-detector-1.1.3+neoforge.jar
26 May 2025
1.1.1+neoforge
unsafe-world-random-access-detector-1.1.1+neoforge.jar
29 Sept 2024
1.1.1+forge
unsafe-world-random-access-detector-1.1.1+forge.jar
29 Sept 2024
1.1.0+forge
unsafe-world-random-access-detector-1.1.0+forge.jar
22 Apr 2023
1.1.0
unsafe-world-random-access-detector-1.1.0.jar
25 Feb 2023
1.0.0
unsafe-world-random-access-detector-1.0.0.jar
4 Feb 2023
Looking for an older file? The official Modrinth project page is in Resources.