Why Pre-Generation Matters

When a player walks into an unexplored part of your Minecraft world, the server has to generate that chunk from scratch on the spot. Chunk generation is one of the most CPU-intensive operations a Minecraft server performs. On a busy server, multiple players exploring in different directions at the same time can drive the server tick time up sharply, causing lag spikes that affect everyone online -- even players who are nowhere near the new terrain.

Pre-generating solves this by doing all the chunk generation work in advance, before any players are on the server. Once a chunk exists on disk, loading it is fast. Exploration stays smooth. The server spends its CPU cycles on players and gameplay instead of world generation. This is especially important for survival servers, SMP servers, and any server where players are expected to explore freely across a large area.

What Chunky Does

Chunky is a Paper/Spigot plugin that generates chunks in a controlled background task. You specify a center point and a radius, and Chunky works outward from that center, writing each chunk to disk as it goes. It respects your server's performance -- you can pause and resume tasks, and it saves progress so a server restart does not lose all the work done so far. For general lag reduction beyond pre-generation, see our server lag reduction guide which covers view-distance tuning and other optimizations that complement pre-generation.

Downloading and Installing Chunky

Chunky is available on Hangar and Modrinth. Download the JAR for your Minecraft version and upload it to your server's plugins/ folder. Restart the server to load the plugin. You should see a line in the console confirming Chunky has loaded. No additional configuration is needed before your first generation run -- the defaults are sensible for most setups.

Chunky requires Paper or Spigot. It will not load on vanilla. If you are still on vanilla and want to pre-generate, migrating to Paper first is worth it for the performance benefits alone. Our Paper setup guide walks through the migration in a few minutes.

Running a Generation Task

All Chunky commands are run from the in-game console or the server console in your panel. The typical workflow for pre-generating a 5,000-block radius around world spawn is:

/chunky world world
/chunky center 0 0
/chunky radius 5000
/chunky start

Breaking that down: /chunky world world selects the overworld (named world by default). /chunky center 0 0 sets the center of the generation area to coordinates 0, 0 -- your world spawn. /chunky radius 5000 tells Chunky to generate everything within 5,000 blocks of that center. /chunky start begins the task.

A 5,000-block radius covers a 10,000 x 10,000 block area, which is roughly 390,000 chunks. That is a reasonable size for a small-to-medium survival server. For a larger server or a server where players are expected to spread out significantly, consider a 10,000-block radius, keeping in mind that disk usage scales with the square of the radius.

You can also pre-generate the Nether and End using /chunky world world_nether and /chunky world world_the_end with smaller radii -- 2,000 to 3,000 blocks is usually enough for the Nether since players rarely explore as far there.

Monitoring Progress

Once a task is running, use /chunky status to see the current progress. Chunky prints the percentage complete, the number of chunks generated, the estimated time remaining, and the current generation speed in chunks per second. On a fast NVMe server, generation speeds of 1,000 to 3,000 chunks per second are normal. On slower disks, expect 200 to 500 chunks per second.

The task runs entirely in the background. Players can be on the server while generation is running, though CPU usage will be higher than normal during the task. If you want to minimize the impact on players, schedule the generation to run overnight or before you open the server to the public for the first time.

If the server restarts during generation, Chunky saves its progress. Run /chunky continue after the server comes back up to resume from where it left off rather than starting over.

To pause a running task: /chunky pause. To cancel and discard the task entirely: /chunky cancel. Canceling does not delete chunks that were already generated -- it only stops the task from continuing.

How Much Disk Space to Expect

Pre-generated world data takes meaningful disk space. Here are rough estimates for an overworld pre-generation, depending on the terrain type and Minecraft version:

  • 2,500-block radius (roughly 98,000 chunks): 500 MB to 1 GB
  • 5,000-block radius (roughly 390,000 chunks): 2 GB to 4 GB
  • 10,000-block radius (roughly 1,560,000 chunks): 8 GB to 16 GB

Worlds with heavy cave generation, ocean biomes, and complex terrain tend toward the higher end of those ranges. These figures are for unmodified chunk data before any player activity. As players build, the stored data per chunk increases. Make sure your server has enough disk headroom before starting a large pre-generation. On NetSkyway, you can check your current disk usage in the panel at any time.