
Modrinth · Minecraft mod
Worldgen Devtools
A mod that aids in the development of world generation data packs and mods. Allows reloading worldgen data packs in-game and resetting chunks. Colors jigsaw blocks by name and target.
Quick answer
Which Worldgen Devtools release matches 25w15a?
Worldgen Devtools 1.3.1+25w15a targets 25w15a, 25w16a with Fabric. Installation on the client is optional. Installation on the dedicated server is optional. 1 required mod needs a matching file.
Where it goes
Is Worldgen Devtools required on the client, server, or both?
Installation on the client is optional. Installation on the dedicated server is optional.
The source marks this as usable on both the client and server.
What else does Worldgen Devtools 1.3.1+25w15a need?
1.3.1+25w15a on 25w15a. Every mod below is checked against that same setup.
Install Fabric API first, but 1 required mod has no matching file for this setup. Do not mix loader builds to force a match.
We only count dependency files that match this setup. A file for another loader does not fill the gap.
Before you install it
Add Worldgen Devtools without breaking your instance.
Built for Worldgen Devtools 1.3.1+25w15a on 25w15a. Pick another file and the loader, install side or required mods may change.
- 01
Stick to this file
Use 1.3.1+25w15a. It targets 25w15a, 25w16a with Fabric; another release may have different loader, side or dependency requirements.
- 02
Bring the mods it needs
Install Fabric API first, but 1 required mod has no matching file for this setup. Do not mix loader builds to force a match.
- 03
Put it on the correct side
Installation on the client is optional. Installation on the dedicated server is optional.
- 04
Pick the file you checked
Use the “Get this file” button beside 1.3.1+25w15a. It opens that exact file at the source.
About this project
What does Worldgen Devtools add?
Worldgen Devtools
This is a mod that provides tools simlifying the creation of worldgen datapacks and mods.
Registry (worldgen) Reloading
Needs be enabled per world using the reloadRegistries gamerule.
Warning: While this should be fairly stable, this tool can probably still corrupt your worlds. So only enable in testing worlds
Allows the reloading of registry content (such as all worldgen data) using the /reload command, or when enabling or
disabling a datapack using the /datapack command. Without this mod, the world needs to be reopened for changes to take
effect.
Entries are never removed from registries, even when no longer present in the loaded datapacks. Instead, they are marked as
outdated, so that they don't have an effect on world generation and can't be referenced from other datapack files.
Existing chunks can still use the outdated entries though, until the world is reopened. The world-height and noise shape
(i.e. height and cell size) can't be reloaded.
Client Syncronization
Some reloaded data affects the client, such sa biome colors, dimension types, and armor trims. In multiplayer, dimension
and biome effects need to be synconized. This causes the client to redraw all chunks. If this behaviour is undesireble,
it can be disabled using the syncAfterRegistryReload gamerule.
Reset Chunks

The /resetchunks [<range>] command resets the chunks surrounding the player in the specified range - regenerating it with the current worldgen data and settings. Defaults to 0 (i.e. only the current chunk). If you want to reset a structure, you need to reset the chunk of the structure start.
Note: This implementation actually used the normal worldgen thread, and thus has much better performance than the unregistered vanilla command.
Colored Jigsaw Blocks

Colors Jigsaw blocks based on their specified "Name" or "Target Name". If a "Name" other than minecraft:empty is set,
the jigsaw block is colored based on the hash of the "Name". Otherwise, if a "Target Name" other than minecraft:empty
is set, the jigsaw block is colored based on the hash of the "Target Name".
If both "Name" and "Target Name" are set to minecraft:empty the jigsaw block is rendered deactivated, with grayed
out arrows and connectors.
In the inventory, if a jigsaw block has stored NBT (Shift+Pick), then it is rendered with the associated color and a
tooltip indicated the "Name", "Target Pool", and "Target Name".
Get Density Command
Command to debug the values of density functions are any position.
/getDensity density_function <df> [<pos>]
Returns the value of the density function df at the specified postion (or the position of the player)
/getDensity noise_router <entry> [<pos>]
Returns the value of the density function specified in the given entry of the noise router of the current dimension at
the specified postion (or the position of the player)
Profiling of Worldgen Performance

The time it took to generate each step of each chunk is recorded and saved in each chunk. To access it, use
the /chunkprofiling <range> command. Range controlls the amount of chunks to average the performance over; defaults
to 0.
Locate Feature

Use /locate feature <configured_feature> to locate a configured feature nearby. If the current chunk contains the feature
multiple times, it will list the up to 5 closest positions. This only works if the chunk is generated while this mod is
installed.
Logging improvements
- Empty height ranges in placed features also log the placed feature that causes the problem.
Chase
The /chase command provides options to syncronize of the player positions between two different instances of Minecraft. Usefull for
comparing differences in worldgen. This is a vanilla command, simply registered by this mod.
Gamerules
Gamerules added by this mod:
| Gamerule | |
|---|---|
maxChunkStatus |
Which steps of world generation should be done? -> NOISE_ONLY: Generates stone, air, water and lava only. -> SURFACE: Applies the surface rules. -> SURFACE_AND_CARVERS: Applies surface rules, and carvers. -> ALL: Applies surface rules, carvers, and features. |
applyProcessorLists |
Should processor lists of structures be applied? |
applyGravityProcessor |
Should terrain matching structure pieces match the terrain? |
keepJigsaws |
Should the jigsaw blocks be kept after structure generation? |
reloadRegistries |
Should the /reload command also reload registries? |
syncAfterRegistryReload |
Should all clients be resend the registry content after reloading? |
saveChunks |
Should chunks be saves? Old chunks are not deleted when disabling. |
Project description from Modrinth.
Pick your setup
Worldgen Devtools by Minecraft version and loader
Choose the version and loader you play, then open the matching release.
26.3-snapshot-2
1 loader build26.2-rc-2
1 loader build26.2
1 loader build26.1.2
1 loader build26.1.1
1 loader build26.1-snapshot-2
1 loader build26.1-snapshot-1
1 loader build26.1-rc-2
1 loader build26.1
1 loader build25w46a
1 loader build25w45a
1 loader build25w44a
1 loader buildShowing the newest 12 of 74 game versions. Older files are in the list below.
Check the dependencies, then try the file in a copied instance before changing a world you care about.
Recent files
Worldgen Devtools versions and loaders
1.3.1+25w15a
worldgenDevtools-1.3.1+25w15a.jar
9 Apr 2025
Looking for an older file? The official Modrinth project page is in Resources.