Description

Concurrent Chunk Management Engine

A Fabric/NeoForge mod designed to improve the chunk performance of Minecraft.

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Benchmarks for 1.21.10 w/ Terralith (Nov 21, 2025)

2t-80t 1t-16t

So what is C2ME?

C^2M-Engine, or C2ME for short, is a Fabric/NeoForge mod designed to improve the performance of chunk generation, I/O, and loading. This is done by taking advantage of multiple CPU cores in parallel. For the best performance it is recommended to use C2ME with Lithium and ScalableLux.

What does C2ME stand for?

Concurrent chunk management engine, it's about making the game better threaded and more scalable in regard to world gen and chunk io performance.

Vanilla parity

C2ME does not sacrifice vanilla functionality or behavior, or alter the vanilla world generation in the name of raw speed by default. However, due to the non-determinism of vanilla world generation, worlds will vary significantly run-to-run even with the same seed. This is not a bug on our side.

While we carefully check that we do not modify any vanilla behavior, bugs are unavoidable after all. So, if you do encounter an issue where C2ME deviates from the intended vanilla behavior, don't hesitate to open an issue.

Mod and Datapack compatibility

World generation datapacks that can run on vanilla Minecraft are fully supported.
Custom world generators implemented in mods usually runs well, but may cause compatibility issues due to certain design assumption used by mod authors being broken for further speedups of world generation.
As a world generation mod author, if you find your mod broken, don't hesitate to look for help in our discord server (linked below). We are willing to help mod authors to embrace scalable world generation.

Undefined behavior sanitization

C2ME includes CheckedThreadLocalRandom for world random (included in UWRAD) plus a few others. These detections exist to prevent mods from screwing up Minecraft internals and causing undebuggable problems.
The detection should almost never produce false positives, and should be taken seriously and reported to corresponding mod authors instead.

Usage notice

Backup your worlds and practice good game modding skills.

Support status for Minecraft versions

Only the latest Minecraft release and the latest Minecraft snapshot are fully supported. Older Minecraft releases are in long-term support and will receive critical bug fixes. Older Minecraft snapshots are not supported.