FairPlay overview

FairPlay is a Bukkit-family anticheat focused on combat compensation. It reads packets through PacketEvents, evaluates combat, aim, interaction and timing checks, and can either alert, cancel/modify the action, or apply a configured mitigation. It is not a movement-prediction anticheat and does not claim to replace one.

The source was inspected for this documentation, but the license is Personal Use Only, not an open-source license. Commercial use, redistribution and publishing modified or unmodified copies require prior written permission.

Field	Verified value
Version	4.1.0
License	Personal Use Only; non-commercial, no redistribution
Main class	com.arkflame.fairplay.FairPlayPlugin
Plugin metadata	api-version: 1.13, folia-supported: true
Bytecode	Java 8 source/target
Build API	Spigot 1.21.11-R0.1-SNAPSHOT
Required dependency	PacketEvents, external and not shaded
Optional hooks	GrimAC, Vulcan and other soft dependencies

What it evaluates

The plugin ships check modules for aimbot, autoclicker, AutoTotem, fastbreak, hitbox, killaura, scaffold and timer families, plus protocol and inventory checks. Checks are registered from packages at startup and can be listed or toggled with /fp checks and /fp toggle.

The README calls the current production posture combat-only and points at ToggleCommand and FairCheckManager for which checks are enabled in a given build. Treat the shipped check tree as available configuration, not as a promise that every module is active on your server.

FairPlay does not ship fly, speed, vertical-prediction, movement-simulation, velocity-prediction or replay-baseline checks. Movement packets, locations and rotation history are kept as shared telemetry for combat, aim, hitbox, scaffold and timing checks. That boundary is deliberate: a combat decision should be explainable from the packets that produced it.

How a packet reaches a decision

1. Receive once. The PacketEvents listener deduplicates events by event identity before dispatch, so two listeners cannot apply the same compensation twice.
2. Dispatch by packet type. Dedicated handlers process attacks, swings, block placement, inventory clicks and the rest, each with a stage label.
3. Evaluate checks. Check modules return results. A hitbox attack decision aggregates independent results and cancels when any result is a failure; PASS and UNKNOWN are not cancellation reasons.
4. Resolve latency. The transaction service selects AUTO, GRIM, NATIVE or DISABLED at startup. AUTO uses Grim when its API is available and native markers otherwise. If Grim is detected but its API fails, the service reports GRIM_UNAVAILABLE and keeps native markers disabled to avoid a packet-owner collision; Polar or Vulcan ownership selects a conflict mode instead of stacking transaction sources.
5. Apply policy. Detection and mitigation are separate. The punishment and mitigation configuration decides whether a failure produces an alert, a cancellation, a kick or a ban.

Reach compensation is a specific path: after a reach-increase punishment, an eligible main-hand AIR swing can apply melee damage against a nearby target within the configured compensated-reach band. It is not a general reach extension applied to every attack.

Requirements

Requirement	Verified detail
Server	Bukkit, Spigot or Paper; folia-supported: true is declared
API metadata	api-version: 1.13
Java	Java 8 bytecode; use the JVM your server version requires
Packet layer	PacketEvents required; FairPlay disables itself when it is absent or not external
PacketEvents build	Compiled against 2.14.0; no minimum version is declared
Optional hooks	GrimAC, Vulcan, NoCheatPlus, PolarLoader, Intave, Matrix, Spartan
Storage	YAML by default under storage/players

PacketEvents is a hard depend in plugin.yml and is also checked at runtime. FairPlay verifies that the loaded PacketEvents API is external and disables itself rather than shading or replacing it.

What is not claimed

• The README statement “Minecraft 1.8–1.21” is a claim, not a tested compatibility matrix. The build targets Spigot 1.21.11 only.
• The Folia flag is metadata. No Folia runtime test is documented in the audited source.
• No minimum PacketEvents version is declared; the build compiles against 2.14.0.
• “All checks active” is not a safe assumption; toggles and per-check YAML decide.
• The license does not permit commercial deployment or redistribution without permission.

For deployment see install FairPlay. For administration see commands and permissions. The FairPlay case study covers the packet pipeline and cancellation authority.

Verified against FairPlay aad8a638 (version 4.1.0, 29 October 2026) on 30 October 2026. Metadata, defaults and code paths come from source; no live server or Folia run was performed.