Unsafe World Random Access Detector (NeoForge)
Java mod listed for Minecraft 1.21. Downloads from the MC Java Mods app on Android.
This is a mod that detects unsafe off-thread world random access, helping to find causes of "Accessing LegacyRandomSource from multiple threads" crash.
⬇ Download on CurseForgeThe author built this one for Minecraft 1.21–1.21.5 on NeoForge. On other versions it may install and then do nothing.
Unsafe World Random Access Detector (Forge)
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.
Looking for fabric versions? Looking for forge versions?
- Edition: Minecraft Java
- File type: .jar
- Minecraft versions listed: 1.21, 1.21.1, 1.21.5
- 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 unsafe-world-random-access-detector-1.1.3+neoforge.jar — drop this file into the mods folder
- Download size: 22 KB
- Download link checked 27 Sept 2026 — working
These come from our own check of the pack file, not from the source page.