Frequently Asked Questions

All iris questions that we can think of will be put here
There is a table of contents on the right

When to update Iris

Updating Iris is not like any other plugin. To draw a comparison between Iris and Mojang - When you update your server's Minecraft version, it will result in any new chunk that is generated to not be aligned with existing chunks, in every vanilla world.
Iris generates worlds for you as well, so it has the same problem. The difference is that Iris updates a lot, and Mojang barely, which makes users think it is safe to update, when in reality, it may do more harm than good.
A quote from our lead developer:
Generally its not possible to do something like that without ending up with hard borders / having to edit millions of chunks possibly. By changing the biome map, everything changes. Things that were a desert are now a forest. I could blend it by using an interpolator, but... ignoring the intense CPU [required for] that, it would still look terrible, because it would still look like a wall, just smoother, and the biomes would still be hard-cut. Just update when your ready to make a new map, its not a big issue 😛

So, when should you update Iris?

You should only update Iris when you are ready to delete or recreate all Iris worlds. If you are even thinking about updating Iris in any other case, contact support to discuss it first.
Always Make Backups FIRST
If you are sure you want to update Iris, see Updating the Overworld.

How to change the seed in Iris

Iris worlds, as opposed to normal vanilla worlds, generates new worlds with the same seed every time. To change this seed, you have to add it to the file, which you find in your main server directory (*/ Just locate the level-seed= setting and add any number behind it, at random. Every time you change this, and generate a new Iris world, you will have new random generation.

Out of bounds error

To fix it, Actually let the server restart when you see the plethora of errors instead of proceeding to make worlds (we say to restart in the error at the bottom, and in bold, and in red, and in game, so yea you need to restart)
Contact the Discord if you need further help with this one

Manually downloading the Overworld

  1. 1.
    Stop the server
  2. 2.
    Remove */plugins/iris/packs/overworld (the folder)
  3. 4.
    Place it in the same folder as before, */plugins/iris/packs/overworld
  4. 5.
    Unzip the folder
  5. 6.
    Rename the resulting folder to overworld
  6. 7.
    Follow the getting started tutorial as you are used to from here

Restart after downloading a pack

This is related to the requirement that Datapacks are already installed upon server startup, while Iris is not ready before startup. Iris uses Datapacks to make amazingly colored biomes such as the Sakura biome:
Iris' Sakura Forest

Red logo on startup (Mac only)

The broken console logo
Set in the settings.json Configuration -> General -> useConsoleCustomColors to false
The fixed console logo

Uninstalling Iris

There are many things Iris controls which will break when you uninstall the plugin. A lot of these features may cause issues in survival servers so we strongly recommend keeping Iris installed.
Features that are likely to break:
  • Strongholds cannot be found with eyes of ender: Iris allows you to directly control how many strongholds can spawn and how far apart they are. Because we don't follow the same method as vanilla, eyes of ender require Iris to be installed to lead to the correct locations. If you uninstall Iris, eyes of ender will lead to locations where there is nothing (where vanilla would place one)
  • No mob and animal spawns: Iris does not spawn mobs when it generates chunks, but instead has its own spawning system to evenly distribute mobs/animals over the entire server. These mobs will no longer spawn. Mobs that spawn in structures like silverfish and guardians will no longer spawn.
  • New chunks will not be custom: New chunks will be normal vanilla chunks which do not align properly with existing chunks. Removing these manually can be difficult if you wish to amend it.
  • Custom particle & sound effects will disappear: There are custom particles & sound effects which will no longer be (dis)played and replaced by (boring) vanilla defaults. Iris uses these to add biome immersion, and all of this would be removed.
  • Custom leaf decay systems: Iris spawns custom trees which have leaves which are too far away from logs without them decaying. Iris controls leaf decay systems and uninstalling the plugin may result in leaves being removed where they shouldn't.
  • Custom height modifications: Iris is responsible for setting the max height to something different than vanilla. If you remove Iris, this will not be ensured with every world and you may end up with mountains cut-off at the new - wrong - build limit.
  • World Shifting: A less probably bug but one that can still seriously mess up your worlds is that certain parts of the world may be shifted up 64 blocks. This allows people to get below the bedrock, breaks the terrain and can even cut player-built buildings in half.
If you decide to uninstall Iris because of issues with server performance (Iris seems to be causing lag), please contact support first, so we can search for a solution. We would then love to see a timings report, /timings report.

Biomes larger / smaller

Diagram of Dimension settings' effects
In this diagram, you see what settings affect biome sizes. To make biomes larger, you can increase the zoom on the region's specific biomes here, which will make the collection of biomes that are in a category larger. You can also change all biome & region sizes to be larger, this setting is found here.

Change object spawn chance

To reduce the number of times an object spawns in a single area, follow the following steps:
1. Find the name of the object by getting an Object Dust with /iris object dust and clicking the object. Remember this name, we need it in step 4.
2. Find the name of the biome by running /iris find
3. Open the configuration file for the biome by locating it in the */plugins/iris/packs/overworld/biomes folder. Each of the folders in there is for one region. The name of the region is included in the name of the biome. Open the biome file. (If you are in a studio world, you can use /iris studio editbiome to directly open the file)
4. Find the "objects" section, which looks similar to the following (more or fewer settings may be present)
"objects": [
"place": [
"chance": 0.1,
"density": 2,
"mode": "MIN_HEIGHT"
In here, there are 2 options to take into account, chance and density.
Chance dictates the fractional chance of an object spawning per chunk, if it is 0.1, it has a 1 in 10 or 10% chance of spawning. You can decrease this number to decrease the number of times it spawns.
Density dictates the number of times the object spawns if the chance roll was successful. So, for example, if the 10% chance of the example is successful, there are going to be 2 objects of the objects included in the place list, in that chunk. You can decrease this number to see less clusters of objects spawning.
Another option is to remove one or more of the objects from the list under place, this will remove that object from the biome entirely. Note: Do not remove all objects from the list. Instead, set the chance to 0.

Disable Iris Spawn System

You can disable the Iris spawn system in the config *\plugins\iris\settings.json and look for "anbientEntitySpawningSystem": true, and "markerEntitySpawningSystem": true, and set those to false


We offer support on our Discord. Ask questions you cannot answer using the Wiki there. We ask you to look on the wiki for a solution for your issue before going there. Thank you for using Iris!
  • The Volmit Software Team