Grim Anticheat

GrimAC is an free open source Minecraft anticheat designed to support the latest versions of Minecraft. It currently supports minecraft versions 1. 8-1. 21. Geyser players are fully exempt.

This project is considered feature-complete for the 2. 0 (open-source) branch. If you would like a bug fix or enhancement and cannot sponsor the work, pull requests are welcome. A premium version is planned, which will offer additional subscription-based paid checks, such as heuristics.

## Installation notes - Java 17 is now required. More information (https://github.com/GrimAnticheat/Grim/wiki/Updating-to-Java-17). - Paper, Spigot, and Folia are currently supported. - If you use Geyser, place Floodgate on the backend server so grim can exempt bedrock players. Grim cannot access the Floodgate API if it is on the proxy. - If you use ViaVersion, it should be on the backend server as movement is highly dependent on client version.

## Support & wiki information - Support & discussion: (https://discord.grim.ac) - Report issues: (https://github.com/GrimAnticheat/Grim/issues/new/choose) - Wiki & examples: (https://github.com/GrimAnticheat/Grim/wiki)

## Developer API Grim's API allows you to integrate Grim into your own plugins. - API repository: (https://github.com/GrimAnticheat/GrimAPI) - Wiki info: (https://github.com/GrimAnticheat/GrimAPI)

## How to compile

1. `git clone https://github.com/GrimAnticheat/Grim.git` 2. `cd Grim` 3. `./gradlew build` 4. The final jar will compile into the build/libs folder

## Grim supremacy

What makes Grim stand out against other anticheats?

### Movement Simulation Engine

We have a 1:1 replication of the player's possible movements This covers everything from basic walking, swimming, knockback, cobwebs, to bubble columns It even covers riding entities from boats to pigs to striders Built upon covering edge cases to confirm accuracy 1. 13+ clients on 1. 13+ servers, 1. 12- clients on 1. 13+ servers, 1. 13+ clients on 1. 12- servers, and 1. 12- clients on 1. 12- servers are all supported regardless of the large technical changes between these versions. The order of collisions depends on the client version and is correct Accounts for minor bounding box differences between versions, for example: Single glass panes will be a + shape for 1. 7-1. 8 players and for 1. 9+ players 1. 13+ clients on 1. 8 servers see the + glass pane hitbox due to ViaVersion Many other blocks have this extreme attention to detail. Waterlogged blocks do not exist for 1. 12 or below players Blocks that do not exist in the client's version use ViaVersion's replacement block Block data that cannot be translated to previous versions is replaced correctly All vanilla collision boxes have been implemented

### Fully asynchronous and multithreaded design

All movement checks and the overwhelming majority of listeners run on the netty thread The anticheat can scale to many hundreds of players, if not more Thread safety is carefully thought out The next core allows for this design

### Full world replication

The anticheat keeps a replica of the world for each player The replica is created by listening to chunk data packets, block places, and block changes On all versions, chunks are compressed to 16-64 kb per chunk using palettes Using this cache, the anticheat can safely access the world state Per player, the cache allows for multithreaded design Sending players fake blocks with packets is safe and does not lead to falses The world is recreated for each player to allow lag compensation Client sided blocks cause no issues with packet based blocks. Block glitching does not false the anticheat.

### Latency compensation

World changes are queued until they reach the player This means breaking blocks under a player does not false the anticheat Everything from flying status to movement speed will be latency compensated

### Inventory compensation

The player's inventory is tracked to prevent ghost blocks at high latency, and other errors

### Secure by design, not obscurity

All systems are designed to be highly secure and mathematically impossible to bypass * For example, the prediction engine knows all possible movements and cannot be bypassed