GrimAC
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 here.
- 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
Developer API
Grim's API allows you to integrate Grim into your own plugins.
How to compile
git clone https://github.com/GrimAnticheat/Grim.gitcd Grim./gradlew build- 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
