Nothing kills the exploration experience faster than chunk generation lag. When a player walks into unloaded territory, the server has to generate terrain, caves, structures and biomes on the fly. That takes a lot of CPU, and the TPS drop hits everyone online.
What Is Chunk Pre-Generation?
Minecraft worlds generate lazily: chunks only exist once someone (or something) loads them. Pre-generation makes the server create chunks in advance and save them to disk, so later visits are a quick load from disk instead of an expensive generation job.
For modded servers, this is even more critical. Modded terrain generation (biomes, structures, ores from tech mods) is significantly more expensive than vanilla.
Installing Chunky
Paper/Spigot/Purpur
- Download Chunky from Modrinth or SpigotMC
- Drop the JAR in your
plugins/folder - Restart the server
Fabric
- Download the Fabric version from Modrinth, plus Fabric API, which Chunky needs on Fabric
- Place both in the
mods/folder - Restart
Chunky also has Forge and NeoForge builds on the same Modrinth page.
Running Pre-Generation
Basic command:
/chunky radius 5000
/chunky start
This generates everything within 5,000 blocks of the center, a 10,000 x 10,000 block area. Chunky's defaults are a square shape centered on 0,0 (Chunky wiki). If your world spawn is not near 0,0, run /chunky spawn first to center the task on spawn.
Recommended Radii
| Server Type | Radius | Chunks (square, rounded) |
|---|---|---|
| Network Lobby | 500 | about 4,000 |
| Small Survival | 3,000 | about 141,000 |
| Standard Survival | 5,000 | about 391,000 |
| Large Survival | 10,000 | about 1.56 million |
The chunk counts are arithmetic, not measurements: a chunk is 16 by 16 blocks, so a 5,000 radius square is 625 by 625 chunks. Doubling the radius gives four times the chunks, and roughly four times the time and disk space.
How long it takes and how much space it uses depends on your CPU, the Minecraft version and your mods. Chunky tells you the time once it is running (see below). For disk space, run a 1,000-block radius first, check how much the world's region folder grew, and scale by area: a 5,000 radius covers 25 times as much.
Advanced Options
Generate a different shape (square is the default):
/chunky shape circle
/chunky radius 5000
/chunky start
Generate the Nether and End:
/chunky world world_nether
/chunky radius 2000
/chunky start
World names differ between server software and versions. Type /chunky world and press Tab to see the exact names on your server.
Pause and resume:
/chunky pause
/chunky continue
Performance During Pre-Generation
Pre-generation is CPU-intensive, and the speed you get depends on the CPU, the Minecraft version and how heavy the worldgen is. Modded terrain is much slower to generate than vanilla.
You do not have to guess. While a task runs, Chunky prints progress lines with the percentage done, an ETA and the current rate in chunks per second, and when it finishes it prints the total time. /chunky progress shows the same in game. Write the rate and total time down; they are the real numbers for your server and your pack.
Tips for running pre-gen:
- Run it during off-peak hours or before your server opens
- It does not need to finish in one session:
/chunky continuepicks up where you left off - Watch
/spark tpswhile players are online. If tick times (MSPT) climb toward 50 ms, the point where TPS starts to drop below 20, run/chunky pause
When to Pre-Generate
- Before server launch: Always. Pre-gen at least a 3,000-block radius before opening to players.
- After version updates: New Minecraft versions often change terrain generation. New chunks will look different from pre-generated ones, which creates visible seams. Consider pre-generating further out, or starting a fresh world for a new season.
- Before events: If you're hosting an exploration event, pre-gen the target area.
- After adding terrain mods: Mods that change world generation will only affect newly generated chunks. Pre-gen ensures consistency.
World Border
Pair pre-generation with a world border to prevent players from going beyond pre-generated terrain:
/worldborder set 10000
/worldborder center 0 0
This sets a 10,000-block diameter (5,000 radius) border centered on 0,0, matching a 5,000-radius pre-generation with Chunky's default center. You can also set the border first and run /chunky worldborder, which copies the border's center and radius into Chunky.
Storage Considerations
Pre-generated worlds use more disk space, because chunks that might never be visited are already saved. Before a big run, check your free space in the panel and use the estimate from the radius section above. Every Space-Node Minecraft plan lists its NVMe storage on the plan cards. World copies or zip archives you keep in the server's own files count toward it too, so leave some margin.
Pre-generation is a one-time job that pays off for the life of your server. Set it running before launch, let Chunky tell you how long it needs, and your players will not run into chunk generation stutter inside the pre-generated area.