VoidAC

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VoidAC is a prediction-based anticheat that simulates every possible player movement server-side. If a player moves in a way that is mathematically impossible, they get flagged - no heuristics, no guessing.

It is a fork of GrimAC and is completely free and open source under the GNU GPL v3.

Discord / Support

Join the community for support, false positive reports, and updates.

What it catches

Geyser/Bedrock players are always exempt - no Bedrock false positives.

Why VoidAC

• Simulation engine - mathematically verifiable, not pattern-based. Speed hacks and flight are impossible to sneak past due to a 1:1 movement replication engine (covers everything from basic walking/swimming to riding entities).
• Low false positives - the engine accounts for lag, ViaVersion, ViaBackwards, ping spikes, Optifine FastMath, and many other quirks.
• Latency & inventory compensation - tracks inventory to prevent ghost blocks and queues world changes (like breaking blocks under players) until they reach the client, avoiding false flags.
• Full world replication - maintains a compressed world cache (16-64 kb per chunk) per player to allow safe multithreading, prevent issues with client-side or fake blocks, and eliminate block glitching falses.
• No license key required - drop the JAR in and it works.
• Multi-version & cross-version accuracy - one JAR covers 1.8 clients all the way to 26.1, accurately handling client/server translation, missing blocks, correct collision orders, and minor bounding box changes across versions.
• Folia support - runs natively on threaded-region servers.
• Lightweight & asynchronous - all movement checks, the world cache, and the majority of listeners run entirely on the netty thread. Carefully designed for thread safety without main-thread overhead, scaling to hundreds of players.

Punishment system

VoidAC has a built-in punishment pipeline - no extra plugins needed (though LiteBans is supported for tempbans).

• Auto-punish - kicks or bans automatically once a player hits a violation threshold. Configurable per-check.
• Manual punish - /void punish <player> [duration] with a customizable ban screen.
• Ban wave - queue suspicious players and ban them all at once with a single command. Great for catching ban evasion.

Anti-Xray & StorageESP

VoidAC can configure Paper's built-in anti-xray engine automatically on startup. It also supports Storage ESP decoys - fake chest/barrel/shulker packets are sent to clients to confuse X-ray mods that reveal storage blocks.

Both features are opt-in and configured in config.yml.

Threshold Optimizer

VoidAC includes an adaptive threshold tuning system that learns from real server data to automatically recommend optimal violation thresholds. This eliminates guesswork when configuring punishments.

How it works:

1. Run /void optimizer start to begin collecting flag data
2. Grant trusted/legit players the void.optimizer.legit permission - their flags are treated as false positives
3. Let the server run for 24+ hours with active gameplay
4. Run /void optimizer stop then /void optimizer save to generate recommendations
5. Review the generated threshold-optimizer-report.yml and apply thresholds to punishments.yml manually

Key features:

• Safety multiplier - recommends thresholds at 1.5× the highest legitimate flag to avoid false positives
• Per-check analysis - each check gets independent recommendations based on actual player data
• Minimum sample validation - ignores checks with fewer than 5 legit samples (insufficient data)
• Lightweight - minimal CPU overhead; the optimizer is designed to run continuously

Available commands:

• /void optimizer start - begin collecting flag data
• /void optimizer stop - stop collection (required before saving)
• /void optimizer status - view real-time statistics (checks observed, sample counts, top flagged checks)
• /void optimizer save - generate and save the recommendations report
• /void optimizer discard - clear collected data without saving

The optimizer is opt-in and controlled via the threshold-optimizer.enabled setting in config.yml.

More features are waiting for you in VoidAC!

Commands

Configuration

The config is generated on first start at plugins/Void/config.yml.
VoidAC ships in 13 languages - the language file is selected based on your server locale and written to plugins/Void/ next to the main config.

Available languages: English · German · Spanish · French · Italian · Japanese · Dutch · Polish · Portuguese · Romanian · Russian · Turkish · Chinese

Credits & License

VoidAC is a fork of GrimAC by MWHunter (DefineOutside), licensed under the GNU General Public License v3.0.
VoidAC inherits that license - it is free software. The full license text is in LICENSE.

Copyright © 2026 blackowlzz, MWHunter (DefineOutside) and contributors.

Additional credits: Axionize for upstream bug fixes, and PacketEvents for the packet layer.