Pregenerating your world will enhance performance by a lot. If all the blocks are already placed, your server can handle much more traffic, than when they have to be generated live.
We strongly advise you to use Purpur for the highest possible generation speeds.
"Ready" also means there should not be any players playing on the server while you are pregenerating, because:
  • Main server thread instability caused by simply playing are known to cause pregeneration issues, and
  • The server is under heavy load so players that are playing can and likely will experience a lot of lag (spikes) during play.
  • Pick a size
For selecting the right size we recommend a number between 2.5k and 12.5k. 2.5k is more than enough for 10 players per day, and 12.5k is more than enough for over a hundred players per day.
This is the value you will use as <radius> in the next step.
  • Higher sizes cause increasingly longer generation times.
  • Be prepared to wait hours up to days for your generation to be finished.
  • The time depends on the size of the pregen and the hardware of the server.
  • You can always expand an existing generation -> start small.
  • Iris features a Headless mode, which is slightly less stable but much faster than the normal mode. Turn it on in Configuration > Generator > HeadlessPregeneration.
  • Run the pregen:
    • If you are in the world: /iris pregen start <radius>
    • If you are in the server: /iris pregen start <radius> world=<worldName>
    • If you are in the console: iris pregen start <radius> world=<worldName>
The <worldName> is the name of the world. When entering the command, you may have to select a world. As a player, click the option in chat. As console, type the option in the input bar and hit enter.
The <radius> to select is based on preference and use-case.
Entering a radius of 1000, gives you a 2000 by 2000 world, which means you can travel 1000 blocks in any direction from the center of the world (0, 0). Here is a diagram:
/iris pregen 1000
  • Done!


If you need to restart your server during a pregeneration, it is safe to do so at any time. You can ignore any errors about threads not shutting down.
After starting your server again, resume the pregen with the same command you entered before. Iris will skip any chunks that were already generated.
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