When a player walks into a fresh part of your world, the server has to build that terrain on the spot: biomes, caves, ores, structures, the mobs that come with them. On a busy server that shows up fast. Several players exploring in different directions at once can drag your TPS down for everyone.
Pre-generation takes that work out of play time. You generate the terrain once, it is saved to disk, and every later visit to that area is a load from disk instead of a generation job.
The Chunky Plugin
Install Chunky. It has builds for Paper, Spigot, Folia, Fabric, Forge and NeoForge on Modrinth, and it is the tool most server owners use for this.
Basic usage:
/chunky radius 5000
/chunky start
This pre-generates all terrain within 5,000 blocks of the center. By default Chunky centers on 0,0 and generates a square (Chunky wiki); use /chunky spawn first if your spawn is somewhere else. TPS will dip while it runs, so do it during quiet hours or before the server opens.
Progress monitoring:
/chunky progress
How Long Does Pre-Generation Take?
It depends on the CPU, the Minecraft version, the world and above all the mods. Terrain generation is mostly CPU work, and modded worldgen with many added biomes and structures is much slower than vanilla.
Chunky answers the question for your own server. While a task runs, its console updates show the percentage done, an ETA and the rate in chunks per second, and when the task finishes it prints the total time. Start the task, wait a few minutes for the rate to settle, and read the ETA.
Two things make the estimate easier:
- A 5,000-block radius square is 625 by 625 chunks, about 391,000 chunks in total. Doubling the radius gives four times as many.
- If you want a feel for your server first, run a 1,000-block radius, note the total time Chunky prints, and scale up by area. A 5,000 radius has 25 times the area of a 1,000 radius.
Space-Node plans use NVMe storage. For pre-generation, the CPU and the mod list usually matter more than the disk.
Choosing Your Radius
| Server Type | Recommended Radius |
|---|---|
| Small private SMP (10 to 20 players) | 3,000 blocks |
| Public survival server (around 50 players) | 6,000 blocks |
| Large network hub | 8,000 to 10,000 blocks |
| Skyblock (no terrain) | not needed |
Combine with World Border
Pre-generation only helps if players stay inside the pre-generated area. Set a matching world border:
/worldborder set 10000
This sets a 10,000-block diameter, so 5,000 blocks in each direction from the border's center (0,0 by default). You can also do it the other way round: set the border first, then run /chunky worldborder so Chunky uses the border's center and radius.
When players reach the border, they cannot walk into ungenerated terrain, and your pre-generated chunks carry all the load from then on.
Modded Servers: Special Considerations
Modpacks add biomes and structures from dozens of mods, and generation time grows with them. On a large pack like ATM10, plan the pre-generation as a job for before launch or overnight, and let Chunky's ETA tell you how long it really takes.
Start the server fully once and let every mod finish loading before you run Chunky, then start the task from the console. If the pack changes its worldgen in an update, only newly generated chunks get the new terrain.