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NXAntiCheat

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What NXAntiCheat is

NXAntiCheat is a free server-side anti-cheat plugin for Paper 1.21 or newer, requiring Java 21. It analyzes behavior received by the server without a client component or binary inspection. Its listed combat checks examine attack intervals through click entropy and player rotation through yaw-delta patterns and rotation quantization. Each check builds a violation level that decays over time, with punishment triggered only after a configured threshold is crossed. The default ladder kicks players for offenses one and two, applies a 30-day ban for offense three, and permanently bans offense four. UUID-based offense history is stored in punishments.yml for 120 days, while bans use Paper’s profile ban list. The /nxac commands list checks, show violation and offense counts, and clear history. Both checks begin with punishment disabled for calibration.

Who it suits

NXAntiCheat suits operators of Paper servers running 1.21 or newer who want server-side combat checks. It is intended for administrators able to review alerts and adjust thresholds before enabling punishment.

What it does well

No client-side component required
Violation levels decay over time
Provides configurable punishment thresholds
Paper pardon command works with bans
Released under the MIT License

What to know first

Requires Paper 1.21 or newer
Requires Java 21
False positives can follow latency spikes
Punishment is disabled initially

Verdict

NXAntiCheat provides focused behavioral checks and a staged punishment ladder for Paper servers. Operators should calibrate alert-only mode because the project warns about several false-positive conditions.

Facts from NXAntiCheat's own pages

Administration: The /nxac commands list checks, show a player's violation levels and offense count, and reset offense history. · github.com, 11 Oct 2026
Ban management: Bans are written to the Paper profile ban list, so Paper's /pardon command works normally. · github.com, 11 Oct 2026
Build and download: The README says to build with ./gradlew build and that the compiled JAR is written to build/libs/. · github.com, 11 Oct 2026
Calibration: Both checks ship with punishment disabled; the README recommends alert-only operation to collect server data and adjust thresholds before enabling punishments. · github.com, 11 Oct 2026
Calibration and false positives: Both checks ship with punishment disabled, and the README warns that latency spikes, low frame rates, and controller input can cause false positives. · github.com, 11 Oct 2026
Combat checks: The listed checks analyze attack-interval patterns with click entropy and yaw-delta patterns with rotation quantization. · github.com, 11 Oct 2026
Commands: The /nxac commands list checks and thresholds, show a player's violation and offense counts, and clear a player's offense history. · github.com, 11 Oct 2026
Detection: Detection uses behavioral analysis of what the server receives, with no client-side component or binary inspection. · github.com, 11 Oct 2026
False positives: The README warns that latency spikes, low frame rates, and controller input can produce false positives. · github.com, 11 Oct 2026
History retention: Offense history is stored per player UUID in punishments.yml and expires after 120 days. · github.com, 11 Oct 2026
Intended users: The project is described for Paper server operators through its server-side plugin description and Paper requirements. · github.com, 11 Oct 2026
License: The repository lists the project under the MIT License. · github.com, 11 Oct 2026
Offense history: Offense history is stored per UUID in punishments.yml and expires after 120 days; bans use the Paper profile ban list. · github.com, 11 Oct 2026
Permissions: The plugin documents admin, alert, and bypass permission nodes, with the first two defaulting to op and bypass defaulting to false. · github.com, 11 Oct 2026
Product: NXAntiCheat is a server-side anti-cheat plugin for Paper 1.21. · github.com, 11 Oct 2026
Punishments: The listed offense ladder is a kick for offenses one and two, a 30 day ban for offense three, and a permanent ban for offense four. · github.com, 11 Oct 2026
Requirements: The plugin requires Paper 1.21 or newer and Java 21. · github.com, 11 Oct 2026
Violation handling: Each check accumulates a violation level that decays over time, and punishment triggers only after the configured threshold is crossed. · github.com, 11 Oct 2026

Where NXAntiCheat stands on Freedom251

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