GrimAC is an open source minecraft anticheat designed for the latest versions of minecraft with support for versions 1.8 and higher. Geyser players are fully exempt from the anticheat to prevent false positives. This project is currently free and open source, but future versions will eventually become paid and/or will include additional subscription based paid checks. If you would like a bugfix or enhancement and cannot sponsor the work, pull requests are welcome.
- For documentation and examples visit the Wiki.
- For answers to commonly asked questions visit the FAQ.
- For community support and project discussion join our Discord.
- Java 17 or higher. For more details see Updating-to-Java-17.
- A Spigot, Paper, Folia, or Fabric server environment. For more details see Supported-environments.
- 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.
Grim's plugin API allows you to integrate Grim into your own plugins. Visit the plugin API repository for the source code and more information.
git clone https://github.com/GrimAnticheat/Grim.gitcd Grim./gradlew build- The final jars will compile into the
<platform>/build/libsfolders
See Contributing for more information about contributing and what our guidelines are.
What makes Grim stand out against other anticheats?
- 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
- 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
- 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.
- 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
- The player's inventory is tracked to prevent ghost blocks at high latency, and other errors
- 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
