World Pregeneration with Chunky: How to Eliminate Flight Lags Forever
Every Minecraft server owner has faced this scenario: the player count grows, players begin actively exploring the world, using elytras, flying fast in creative mode, or riding boats on blue ice. At that exact moment, the server's TPS (Ticks Per Second) drops sharply from a healthy 20.0 down to 12.0 or lower. The hosting console starts spamming warnings: Can't keep up! Is the server overloaded?.
In 90% of cases, these lags are not caused by faulty plugins or complex redstone circuits, but by generating chunks on the fly. In this article, we will examine why this process places such a massive load on the hosting CPU and how the Chunky plugin allows you to solve this problem once and for all before your server officially opens.
Why On-the-Fly World Generation Kills Your CPU
When a player steps onto unexplored territory, the server has to perform a colossal amount of mathematical calculations in real time. The processor must:
- Calculate the landscape geometry (Perlin noise, mountains, caves, canyons).
- Determine biomes, ore distributions, and block placement.
- Generate complex structures (trees, villages, dungeons, nether fortresses).
- Calculate initial lighting (Light Updates) for millions of blocks simultaneously.
Since standard Minecraft server cores execute these tasks on the main thread, the server literally freezes while waiting for the CPU to finish processing the world geometry. The faster a player travels, the more chunks per second their client requests, causing the server to fall further behind.
The Solution: Separate the processes of generation and reading. If we pregenerate the world beforehand (for example, within a 5,000-block radius), the server will simply read pre-existing region files from the hosting server's fast SSD/NVMe drive when a player flies through. Reading files strains the CPU dozens of times less than generating them from scratch.
Step-by-Step Configuration and Commands for Chunky
The Chunky plugin is currently the most efficient, safe, and fast tool for world pregeneration on Paper, Purpur, and their forks. It runs seamlessly in the background and consumes almost no RAM.
Step 1: Installing the Plugin and Setting the World Border
Before launching the generation, it is essential to set a rigid world border so players cannot physically cross into unprepared territories.
- Install the Chunky plugin into your server's
plugins/folder and restart the server. - Set the world border using the built-in Minecraft command (e.g., a 5,000-block radius from spawn):
/worldborder set 10000
(Note: You must specify the total diameter, which means 5,000 blocks in every direction from the coordinates 0,0).
Step 2: Selecting the World and Shape
All commands can be entered either in-game (with operator status) or directly into your hosting control panel's console (omit the forward slash / when using the console).
Select the world you want to pre-load (the default is world, use world_nether for the Nether, and world_the_end for the End):
/chunky world world
Set the center point from which the generation will expand (usually the spawn point or coordinates 0, 0):
/chunky center 0 0
Set the shape of the generation zone. It is highly recommended to use a circle (circle) since it aligns perfectly with the standard Minecraft world border:
/chunky shape circle
Step 3: Setting the Radius and Launching
Set the generation radius in blocks. A recommended radius for classic survival gameplay ranges from 5,000 to 10,000 blocks:
/chunky radius 5000
Launch the pregeneration process with the main execution command:
/chunky start
Managing the Process and Useful Commands
The generation process can take anywhere from a few hours to an entire day depending on your hosting plan's CPU power and the chosen radius. You can manage the process using these commands:
/chunky silent— disables regular progress update spam in the console (reduces unnecessary load on log files)./chunky pause— temporarily halts the generation (useful if you need to run tests or let players join briefly)./chunky continue— resumes the generation from the exact point where it was paused./chunky cancel— completely cancels the current task.
How Much Disk Space Will the Generated Map Take?
Before launching, make sure your hosting plan has enough free space on its SSD drive. Here is an approximate breakdown of world sizes (for a standard Overworld):
| World Radius (from center) | Total Area (in blocks) | Approximate Disk Size (HDD/SSD) |
|---|---|---|
| 3,000 blocks | 6,000 x 6,000 | ~ 2.5 — 4 GB |
| 5,000 blocks | 10,000 x 10,000 | ~ 6 — 9 GB |
| 10,000 blocks | 20,000 x 20,000 | ~ 25 — 35 GB |
Pro Tip: Run the world pregeneration strictly before you open server access to players. Combining active chunk generation via Chunky with real-time player activity will immediately overload the CPU and slow down the generation process by 3 to 4 times. The ideal approach is to run /chunky start overnight right before your project launch day.
Troubleshooting Common Issues
Issue 1: Generation speed dropped to 1-2 chunks per second
Cause: The hosting panel has filled the RAM with chunk cache, or the processor is simultaneously handling other heavy tasks (such as the DynMap plugin attempting to render a web map at the same time).
Solution: Pause the generation (/chunky pause), disable web map plugins during the loading process, restart the server via the control panel to clear the RAM, and enter /chunky continue.
Issue 2: Players still cause lag by flying past the world border
Cause: You pregenerated the world with Chunky but forgot to configure or activate a world border boundary, allowing players to escape into ungenerated sectors.
Solution: Ensure that the vanilla /worldborder command is configured properly, or use a companion plugin like ChunkyBorder, which automatically links the pregeneration boundary to a physical wall that blocks players from reaching lag-inducing zones.