Pre-generate your Minecraft world to stop exploration lag

Bigger is not better. Every chunk takes storage, and a 5,000 block radius already covers more than most communities ever walk. Check the free storage in the panel first; a large map can take several gigabytes.

Minecraft saves land in region files of 512 by 512 blocks. Counting them gives a feel for the size of a map:

On the normal game a full region file is usually several megabytes, so a 10,000 by 10,000 map lands in the gigabytes, and terrain mods or datapacks add more. The Nether and the End come on top, each in its own folder.

1. Open the World tab and find Pre-generate the world.
2. Choose how far from spawn to generate.
3. Start it. The panel installs Chunky if it is not there yet and begins generating.
4. Leave the server running. You can follow the progress in the Console.

Run it when few people are online, such as at night. Players can stay on, but the server works hard while it generates.

Chunky is the tool behind the button, and you can drive it yourself from the console for more control, for example to do the Nether as well.

chunky world world
chunky center 0 0
chunky radius 3000
chunky start

• chunky pause and chunky continue stop and resume. Progress survives a restart.
• chunky world world_nether and a smaller radius, since Nether distances count eight times, does the Nether.
• chunky spawn sets the centre to the world spawn instead of 0 0.

On Paper the dimensions are named world, world_nether and world_the_end. On Fabric and Forge, use minecraft:overworld and minecraft:the_nether instead.

When a task is done, the console says it finished, with the number of chunks and the total time.

Pre-generating does not stop players from walking past the edge into new land. A world border does. Set it to the same size as the area you generated. The border takes a width, which is twice the radius:

worldborder center 0 0
worldborder set 6000

That border matches a Chunky radius of 3000. Players who reach it simply cannot go further, and the server never has to generate new terrain again.

One block in the Nether is eight in the overworld. A Nether radius of one eighth of the overworld radius therefore covers every portal players can build inside your overworld area. For a 3,000 block overworld:

chunky world world_nether
chunky radius 375
chunky start

The outer islands of the End start about 1,000 blocks from the centre, and players with elytra fly far. A radius of 3,000 to 5,000 blocks in world_the_end covers most trips.

On Paper each dimension has a border of its own. Set the Nether border from the console with execute in minecraft:the_nether run worldborder set 750, twice the Nether radius.

• Generation speed depends on the world type and mods. A heavy modpack generates far slower than the normal game.
• A Minecraft update that changes world generation, such as new biomes, only applies to chunks that did not exist yet. Pre-generated land keeps the old terrain.
• Generating a new world after a reset? Run it again; the old progress belonged to the old world.

Chunky also runs as a mod on Fabric, Forge and NeoForge, and the commands are the same. Two differences:

• The dimensions have their full names: minecraft:overworld, minecraft:the_nether and minecraft:the_end, and modded dimensions such as twilightforest:twilight_forest when the pack has them.
• Modded terrain is far heavier to generate. Start with a smaller radius, such as 1,500 blocks, and add more later with a bigger radius; Chunky skips the chunks that already exist.

Install a modpack explains why this matters most for big packs.

1. Check with chunky progress that every task is done.
2. Set the world border to the generated area, if you have not yet.
3. Make a backup in the Backups tab. The pre-generated world is the base you never want to generate again, and a restore is quicker than another run.

A bigger world also makes every backup bigger and slower to make. That is one more reason to keep the map no larger than your players need.