Stable enough for a small server. Please report any issues. Currently supporting 1.8-1.18.

Test server with bufferless alerts: test.grim.ac

GrimAC is an open source anticheat designed for 1.18 and supporting 1.7-1.18. It is free while in beta. It will be sold for somewhere between $15 and $25 on SpigotMC and other various websites, without obfuscation, DRM, subscriptions, or other nonsense that plague other anticheats.

Discord: https://discord.gg/FNRrcGAybJ

Here are the main cores that make 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.
• Order of collisions depends on 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 are 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 safety access the world state
• Per player 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 queue'd 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