GDMC HTTP Interface
Minecraft Fabric/Forge Mod that implements an HTTP interface for reading and writing blocks (and more) with an external program or script.
Screenshots
About this Mod
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.
Available Versions
How to Install GDMC HTTP Interface on Your Server
Order Server
Order a Minecraft Java server with at least 4 GB RAM (6 GB recommended).
Set fabric Loader
In the panel under "Egg", select the fabric loader and matching Minecraft version (1.21.11).
Install Mod
Open the mod browser in the dashboard and search for "GDMC HTTP Interface". Click "Install" – done! Alternatively, upload the .jar via SFTP to the /mods folder.
Compatibility
Mod Loaders
Minecraft Versions
1.21.11, 1.21.10, 1.21.4 (+2 more)
Server-side
~ OptionalRecommended RAM
6 GB(min. 4 GB)Frequently Asked Questions
GDMC HTTP Interface server crashes on startup – what to do?
Most common cause: wrong fabric version or insufficient RAM. Check the server log (latest.log) for "OutOfMemoryError" or "Mixin" errors. With Mado Hosting: ensure at least 4 GB RAM is allocated and the loader matches the mod version (1.21.11). You can switch loaders with one click in the panel.
Is GDMC HTTP Interface compatible with fabric and forge and neoforge?
GDMC HTTP Interface officially supports fabric, forge, neoforge for Minecraft 1.21.11, 1.21.10, 1.21.4. Note: Forge and Fabric mods are NOT cross-compatible – pick one loader and stick with it. The Mado dashboard automatically detects incompatible loader combinations.
Server lagging with GDMC HTTP Interface – how to optimize performance?
Recommended RAM: 6 GB (per 5 players). Use /spark profiler to check if GDMC HTTP Interface consumes the most tick time. Common fixes: reduce server view-distance to 8-10, install "performant" or "starlight" as supplementary mods on Forge. With Mado Hosting, your server runs on NVMe SSDs with dedicated CPU cores for minimal latency.
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