World Importer
Moving a build from a singleplayer world onto a multiplayer server has always been a headache. You either rebuild everything block by block, or you wrestle with clunky external tools that spit out schematics and lose half the details along the way. World Importer takes a completely different approach: it reads your local MCA region files directly and pushes the chunks onto a running server in real time, without a restart and without wiping the rest of the map.
What World Importer Actually Does
At its core, World Importer is a mod that uploads and pastes local world MCA region files onto a server. The client parses the MCA binary format, walking through the 4096-byte header and sector offsets to extract compressed NBT chunk by chunk. Those chunks travel over the network to the server, which decompresses the NBT, parses the PalettedContainer for block states and biomes, replaces entire sections, recalculates heightmaps, and loads block entities on the fly.
Once the import finishes, lighting is recalculated automatically and the updated chunks are synchronized with every player online. The client's stale chunk render cache gets cleared too, so what you see is what actually landed on the server. No relogging, no manual relighting, no guesswork.
Supported Versions and Loaders
World Importer for Minecraft covers a solid stretch of modern releases. It works across Minecraft 1.19 through 1.20.6, with builds split by version group: 1.19 to 1.19.2, 1.19.3, 1.19.4, 1.20 to 1.20.1, 1.20.2 to 1.20.4, and 1.20.5 to 1.20.6. Loader support includes Fabric and Forge for the earlier versions, while the newest group (1.20.5 to 1.20.6) runs on Fabric and NeoForge. Architectury API is required, and Mod Menu is optional but handy on Fabric.
Version Directory at a Glance
- 1.19 to 1.19.2 — Fabric + Forge
- 1.19.3 — Fabric + Forge
- 1.19.4 — Fabric + Forge
- 1.20 to 1.20.1 — Fabric + Forge
- 1.20.2 to 1.20.4 — Fabric + Forge
- 1.20.5 to 1.20.6 — Fabric + NeoForge
How to Install World Importer
Installation is straightforward, but there is one rule you cannot skip: the mod must be present on both the client and the server. A client-only setup will not work, because the client does the parsing and the server does the writing.
- Download World Importer for the exact Minecraft version your server runs.
- Drop the jar into the mods folder on both client and server.
- Make sure Architectury API is installed on both sides.
- Restart the server and launch the game.
If you would rather skip the manual file shuffling, the foxygame.net launcher handles the whole routine for you: it detects your installed Minecraft version, matches it against its add-on catalog, and installs World Importer with a single click, keeping dependencies like Architectury API in sync automatically.
Using the Mod In-Game
Join the server, walk to the spot where you want the imported terrain to land, and run /wi setpos. This sets your current standing position as the paste origin, and the center of the source world will map onto that point. Next, run /wi select <path> to point the mod at your local world's region folder, or press K to open the configuration GUI and fill it in there.
When everything is set, run /wi start or click "Start Upload" in the GUI. A HUD appears at the top of the screen showing three progress bars: Importing in green, Lighting Update in cyan, and Syncing Chunks in purple. The server TPS sits beside the bars, color-coded so you can tell at a glance whether the server is keeping up.
Command Reference
- /wi setpos — sets the paste origin at your position.
- /wi select <path> — selects the local region folder.
- /wi start — begins the upload.
- /wi status — checks origin and import progress.
- /wi cancel — stops an ongoing import.
All commands require OP permissions at Level 2, which keeps random players from rewriting your terrain.
Configuration and Traffic Control
Pressing K opens the configuration GUI, where you can tune upload interval, packet size, and light update rate. The defaults are sensible: 5 ticks between chunk uploads, 30 KB packets, and 5 chunks of lighting per tick. Auto-throttle is enabled by default and adjusts the upload interval based on live TPS. Above 18 TPS it uses your configured interval, below 15 it backs off to the maximum of 40 ticks, and values in between are interpolated linearly. The config saves to .minecraft/config/world_importer.json.
A Word of Warning
World Importer overwrites chunks directly. Whatever is in the MCA file replaces whatever is on the server at that location, blocks, biomes, and block entities included. Do not paste into areas with existing builds, and always make a backup before you start. Treat the paste origin like a loaded weapon and aim it at empty terrain.
Final Thoughts
For server owners and map makers who move builds between worlds regularly, World Importer removes one of the most tedious chores in Minecraft. Real-time chunk replacement, automatic lighting, and TPS-aware throttling make it practical even on a busy server. Just pick the right build for your version and loader, install it on both sides, and keep a backup within reach.