Chunkis
by Liparakis
Chunkis is a Fabric optimization mod that replaces vanilla chunk persistence with its own compact binary format, called CIS, for world data.
What it does
Chunkis stores only the chunk changes players make, rather than the full chunk data that vanilla keeps, which reduces the size of world saves. Chunks it has taken over are written to CIS region files, and those files become the authoritative source for them. Chunks still owned by vanilla stay in the Anvil format, so the two can coexist in one world.
Restoring a chunk brings back its blocks, block entities and supported entity metadata when it loads. Unsafe or incomplete chunk payloads are rejected rather than written. Existing vanilla worlds can be brought over through a migration path that also covers external entity regions, and source files are retired only after the migrated data is verified. Chunkis works with singleplayer worlds, integrated servers and LAN-hosted games, and it is tested on dedicated server setups.
Chunkis requires Fabric API and is published for Fabric only. Its files target Minecraft 1.21 – 1.21.11 and its latest file, 4.0.0, is on the beta channel for 1.21.11. The mod is open source under the MIT License and runs on the client and the server.
Key features
Sparse chunk storage
Only player-made changes are persisted, so world save sizes shrink compared with vanilla chunk data.
Compact CIS format
Chunks taken over by Chunkis are saved in a custom binary format with compact region files.
Protected vanilla chunks
Chunks that have not been claimed by Chunkis are left untouched and are never overwritten.
Migration of existing worlds
Vanilla worlds can be imported, and source files are removed only after migrated data is verified and a backup exists.
Compatibility
Latest build for each game version and loader.
1.21.x12 of 12 versions with builds
Only full game releases are shown. This mod publishes no snapshot builds.
Requirements
Dependencies declared by the latest file for each loader.
Required 1
Use cases
Who it’s for: Server owners and players who keep large or long-running worlds and want smaller saves. Because the format replaces vanilla persistence, it suits players willing to back up before testing.
Questions
Does Chunkis need Fabric API?
Does the server need Chunkis?
Can an existing vanilla world be converted?
Which game versions does Chunkis support?
In the catalog
Chunkis is one of 3,545 Optimization mods on ModsFinder, and one of 2,575 Optimization mods for Fabric. 19,862 mods support Minecraft 1.21.11.
Similar mods
What the author says
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.
Official listing
- Modrinth page
- modrinth.com/mod/chunkis
- Owner
- Liparakis
- Published
- 2026-01-21
- Updated on Modrinth
- 2026-07-12
- Facts verified
- 2026-10-15