Smaller world saves without changing gameplay

Worlds grow quietly. Regions, block entities, entities, and repeated chunk data can make backups, transfers, and long-term storage heavier than expected.

Chunkis gives Minecraft a dedicated chunk storage layer designed to keep world data compact and recoverable.

What Chunkis does

Chunkis replaces vanilla chunk persistence with its own CIS format. It:

• stores Chunkis-owned ("claimed") chunk data in compact region files — chunks Chunkis has taken over as the authoritative source, as opposed to chunks still owned by vanilla's Anvil format;
• restores blocks, block entities, entities, and supported metadata when chunks load;
• protects vanilla saves that haven't been claimed by Chunkis from being overwritten;
• rejects unsafe or incomplete chunk payloads;
• supports importing existing vanilla worlds through its migration path;
• works with singleplayer worlds and integrated (LAN-hosted) servers.

Dedicated servers: Chunkis has not been tested on dedicated server setups. If you're running a standalone/dedicated server (not a LAN world hosted from the client), treat this as unsupported until stated otherwise.

Chunkis changes how chunks are stored. It does not add gameplay content, change recipes, or replace rendering.

Why use it?

Benefit	What it means
Smaller worlds in many cases	CIS can avoid redundant storage, but the result depends on the world — see Storage impact.
Easier backups	Smaller saves are faster to copy, upload, archive, and transfer.
Safer, predictable persistence	Chunkis validates ownership and rejects data that can't be reconstructed safely, so restored state is deliberate rather than dependent on accidental vanilla behavior.
No fake performance promises	Chunkis is a storage mod — not an FPS or TPS booster.

Requirements

• Minecraft 1.21.11
• Fabric Loader
• Fabric API
• Java 21 or newer

Installation

1. Install Fabric Loader for Minecraft 1.21.11.
2. Download Fabric API and Chunkis from Modrinth / CurseForge (links TBD), or grab the latest release from GitHub Releases.
3. Place both .jar files in your .minecraft/mods folder (or your server's mods folder, for integrated/LAN hosting).
4. Launch with the Fabric profile.

Compatibility

Chunkis has not been tested against other mods that write or optimize chunk/region data (e.g. lighting engine replacements, other chunk-storage or compression mods). If you're running mods in that category, back up before testing and report any conflicts you find.

Important: Beta software

Before installing:

1. Make a complete backup of your world.
2. Test on a copy or a new world first.
3. Restart the world and verify blocks, block entities, entities, and dimensions.
4. Keep the backup until you are satisfied with the result.

Uninstalling Chunkis is not an automatic rollback. If you need to return to vanilla storage, restore the backup made before Chunkis became authoritative.

Existing worlds

Chunkis can import existing vanilla MCA data through its integrated-server migration path.

The migration checks both normal chunk regions and external entity regions. Source files are only retired after the migrated data is validated and a verified backup is created.

If your world already contains authoritative CIS data, Chunkis treats leftover vanilla region files as stale takeover data. Always keep a backup before allowing this transition.

Storage impact

Chunkis does not guarantee that every world will become smaller. Storage results depend on:

• terrain and block-state variety;
• block entities;
• entities;
• world history;
• other mods that write chunk data.

Benchmark:

A freshly generated, unplayed 2000×2000 region (via Chunky) stored 603 MB in vanilla's region files plus 13.2 MB in its separate entities folder (616.2 MB combined), vs 70 MB in Chunkis 4.0.0's combined format (region + entities together) — an ~88.6% reduction. This is a single benchmark on an unplayed world; played worlds with more block entities and terrain variety will see different results. Community-submitted benchmarks on real, played worlds are welcome — open an issue with your numbers.

FAQ

Will Chunkis improve FPS or TPS?

No general improvement is promised. Chunkis focuses on chunk storage, save/load behavior, and persistence safety.

Is Chunkis always smaller than vanilla?

No — see Storage impact.

Does Chunkis change gameplay?

It does not add gameplay content. It changes how chunk data is persisted and restored.

Can I use it on my existing world?

Yes, via the migration path described in Existing worlds. Back up first — see Beta software.

Does Chunkis work on dedicated servers?

Not tested. Chunkis is confirmed to work with singleplayer worlds and integrated (LAN-hosted) servers. Dedicated server support is untested — proceed with caution and back up first if you try it.

Can I revert to Anvil automatically?

No. Restore your pre-Chunkis backup instead.

What if I find a problem?

Please report it with your Minecraft version, Fabric versions, complete mod list, reproduction steps, latest.log, and crash report if available.

Report a bug on GitHub Read the detailed documentation

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License: [MIT]