GDMC HTTP Interface Mod

Mod for Minecraft (Java Edition) that implements an HTTP interface for reading and writing blocks (and more).

With this interface you can use other applications and scripts running on the same machine to read and modify a Minecraft world.

This is designed as a tool for the Generative Design in Minecraft Competition (GDMC). This annual competition for procedural AI systems in Minecraft, where the challenge is to write an algorithm that generates a settlement while adapting to pre-existing terrain. Feel free to join our community Discord server!

Minecraft version	GDMC-HTTP version	Docs	GDMC competition year
1.21.11	📦 GDMC-HTTP 1.8.4	📒 API Docs	2026
1.21.4	📦 GDMC-HTTP 1.6.0	📒 API Docs	2025
1.20.2	📦 GDMC-HTTP 1.6.0	📒 API Docs	2024
1.19.2	📦 GDMC-HTTP 1.6.0	📒 API Docs	2023
1.16.5	📦 GDMC-HTTP 0.4.2	📒 API Docs	2021, 2022

Usage

When you open a Minecraft world, you will see a chat message that the mod has opened an HTTP connection at the address localhost:9000. This means that you can now send HTTP requests from an external program to Minecraft while the world is open.

For testing and experimentation we recommend an API testing tool such as Kreya, Yaak, HTTPie or a command line tool such as cURL or wget.

When you want to build your own settlement generator or some other application, we recommend using the GDPC Python library, which is purpose-built by the GDMC community to work with this mod. But any programming or scripting language that supports communication over HTTP (which includes most of them, be it either built-in or via an easy-to-use library) will work.

HTTP Endpoints

When the HTTP interface is active, you have access to the following HTTP endpoints:

HTTP method	URL	Description	Docs
POST	/commands	📜 Send Minecraft console commands	📒 API Docs
GET	/blocks	🧱 Get information on blocks in a given area	📒 API Docs
PUT	/blocks	🧱 Place blocks	📒 API Docs
GET	/biomes	🏜️ Get information on biomes in a given area	📒 API Docs
GET	/chunks	⛏ Get raw chunk data in a given area	📒 API Docs
GET	/structure	🏗️ Create an NBT structure file from a given area	📒 API Docs
POST	/structure	🏗️ Place an NBT structure file into the world	📒 API Docs
GET	/entities	🐷 Get information on entities in a given area	📒 API Docs
PUT	/entities	🐷 Summon entities into the world	📒 API Docs
PATCH	/entities	🐷 Edit entities that already exist in the world	📒 API Docs
DELETE	/entities	🐷 Remove entities from the world	📒 API Docs
GET	/players	👷 Get information on players in a given area	📒 API Docs
GET	/buildarea	📐 Get information on the current build area	📒 API Docs
GET	/heightmap	🗺️ Get heightmap information of the build area	📒 API Docs
OPTIONS	/	🪪 Get current Minecraft and mod version	📒 API Docs

Detailed documentation of the endpoints can be found at docs/Endpoints.

Commands

This mod adds the following custom console commands to the game:

Command	Description
/buildarea	Get the current build area, if present. Some endpoints can use the withinBuildArea flag to constrain actions to this area.
/buildarea set <fromX> <fromY> <fromZ> <toX> <toY> <toZ>	Set virtual "build area" to a certain area of the world. For the command arguments you can mix and match absolute, local or relative coordinates.
/buildarea set <fromX> <fromY> <fromZ> <toX> <toY> <toZ> <name>	Set the current build area and store this data under <name> with the save data for later use.
/buildarea load <name>	Load previously set build area.
/buildarea remove	Remove current build area.
/buildarea remove <name>	Remove build area of given <name>.
/buildarea tp	Teleport to within current build area, if present.
/buildarea tp <name>	Teleport to within previously saved build area.
/buildarea list	List all saved build areas.
/buildarea makebook	Give players a book that lists all saved build areas as links that when clicked teleport you to that location.
/buildarea makebook <author>	Create book (see above), signed by <author>. If omitted author defaults to "GDMC".
/gethttpport	Show current port number of the HTTP interface.
/sethttpport	Reset port number of the HTTP interface back to the default 9000.
/sethttpport <number>	Changes port number of the HTTP interface. Useful for when the default port (9000) conflicts with some other application on your machine. You need to reload your world for this setting to take effect.

Acknowledgements

GDMC-HTTP has been actively developed with the help of the GDMC community. Of special note here is Niki Gawlik, who created the original version of this mod for Minecraft 1.16.5. This repo is a continuation of their work. Fabric mod loader support was in part based on a fork by Simon Pribylski. The project structure that makes it possible to support multiple mod loaders and Minecraft versions all on the same branch has been adapted from the Distant Horizons mod.