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Contributing to Modrinth

The vast majority of Modrinth, including everything from our API/backend and frontend to the Minotaur plugin and analytics service, is released under free and open source licenses on our GitHub. As such, we love contributions from community members! Before proceeding to do so, though, there are a number of things you'll want to keep in mind throughout the process, as well as some details specific to certain projects.

Things to keep in mind

Consult people on Discord

There are a number of reasons to want to consult with people on our Discord before making a pull request. For example, if you're not sure whether something is a good idea or not, if you're not sure how to implement something, or if you can't get something working, these would all be good opportunities to create a thread in the #development forum channel.

If you intend to work on new features, to make significant codebase changes, or to make UI/design changes, please open a discussion thread first to ensure your work is put to its best use.

Don't get discouraged

At times, pull requests may be rejected or left unmerged for a variation of reasons. Don't take it personally, and don't get discouraged! Sometimes a contribution just isn't the right fit for the time, or it might have just been lost in the mess of other things to do. Remember, the core Modrinth team are often busy, whether it be on a specific project/task or on external factors such as offline responsibilities. It all falls back to the same thing: don't get discouraged!

Code isn't the only way to contribute

You don't need to know how to program to contribute to Modrinth. Quality assurance, supporting the community, coming up with feature ideas, and making sure your voice is heard in public decisions are all great ways to contribute to Modrinth. If you find bugs, reporting them on the appropriate issue tracker is your responsibility; however, remember that potential security breaches and exploits must instead be reported in accordance with our security policy.

Modrinth currently does not accept monetary donations.

Project-specific details

If you wish to contribute code to a specific project, here's the place to start. Most of Modrinth is written in the Rust language, but some things are written in other languages/frameworks like Nuxt.js or Java.

labrinth (backend and API)

labrinth is the Rust-based backend serving Modrinth's API with the help of the Actix framework. To get started with a labrinth instance, install docker, docker-compose (which comes with Docker), and cargo. The initial startup can be done simply with the command docker-compose up, or with docker compose up (Compose V2 and later). That will deploy a PostgreSQL database on port 5432 and a MeiliSearch instance on port 7700.

Now, you'll have to install the sqlx CLI, which can be done with cargo:

cargo install --git sqlx-cli --no-default-features --features postgres,rustls

From there, you can create the database and perform all database migrations with one simple command:

sqlx database setup

Finally, if on Linux, you will need the OpenSSL library. On Debian-based systems, this involves the pkg-config and libssl-dev packages.

To enable labrinth to create a project, you need to add two things.

  1. An entry in the loaders table.
  2. An entry in the loaders_project_types table.

A minimal setup can be done from the command line with psql:

psql --host=localhost --port=5432 -U <username, default is labrinth> -W

The default password for the database is labrinth. Once you've connected, run

INSERT INTO loaders VALUES (0, 'placeholder_loader');
INSERT INTO loaders_project_types VALUES (0, 1); -- modloader id, supported type id
INSERT INTO categories VALUES (0, 'placeholder_category', 1); -- category id, category, project type id

This will initialize your database with a modloader called 'placeholder_loader', with id 0, and marked as supporting mods only. It will also create a category called 'placeholder_category' that is marked as supporting mods only If you would like 'placeholder_loader' to be marked as supporting modpacks too, run

INSERT INTO loaders_project_types VALUES (0, 2); -- modloader id, supported type id

If you would like 'placeholder_category' to be marked as supporting modpacks too, run

INSERT INTO categories VALUES (0, 'placeholder_category', 2); -- modloader id, supported type id

The majority of configuration is done at runtime using dotenvy and the .env file. Each of the variables and what they do can be found in the dropdown below. Additionally, there are three command line options that can be used to specify to MeiliSearch what you want to do.

.env variables & command line options

Basic configuration

DEBUG: Whether debugging tools should be enabled
RUST_LOG: Specifies what information to log, from rust's env-logger; a reasonable default is info,sqlx::query=warn
SITE_URL: The main URL to be used for CORS
CDN_URL: The publicly accessible base URL for files uploaded to the CDN
MODERATION_DISCORD_WEBHOOK: The URL for a Discord webhook where projects pending approval will be sent
CLOUDFLARE_INTEGRATION: Whether labrinth should integrate with Cloudflare's spam protection
DATABASE_URL: The URL for the PostgreSQL database
DATABASE_MIN_CONNECTIONS: The minimum number of concurrent connections allowed to the database at the same time
DATABASE_MAX_CONNECTIONS: The maximum number of concurrent connections allowed to the database at the same time
MEILISEARCH_ADDR: The URL for the MeiliSearch instance used for search
MEILISEARCH_KEY: The name that MeiliSearch is given
BIND_ADDR: The bind address for the server. Supports both IPv4 and IPv6
MOCK_FILE_PATH: The path used to store uploaded files; this has no default value and will panic if unspecified

CDN options

STORAGE_BACKEND: Controls what storage backend is used. This can be either local, backblaze, or s3, but defaults to local

The Backblaze and S3 configuration options are fairly self-explanatory in name, so here's simply their names:

Search, OAuth, and miscellaneous options

LOCAL_INDEX_INTERVAL: The interval, in seconds, at which the local database is reindexed for searching. Defaults to 3600 seconds (1 hour).
VERSION_INDEX_INTERVAL: The interval, in seconds, at which versions are reindexed for searching. Defaults to 1800 seconds (30 minutes).

The two GitHub OAuth configuration options are also fairly self-explanatory.

RATE_LIMIT_IGNORE_IPS: An array of IPs that should have a lower rate limit factor. This can be useful for allowing the front-end to have a lower rate limit to prevent accidental timeouts.

Command line options

--skip-first-index: Skips indexing the local database on startup. This is useful to prevent doing unnecessary work when frequently restarting.
--reconfigure-indices: Resets the MeiliSearch settings for the search indices and exits.
--reset-indices: Resets the MeiliSearch indices and exits; this clears all previously indexed mods.

Ready to open a PR?

Please ensure the following requirements has been met:

  • cargo check has been ran.
  • cargo sqlx prepare has been ran.

knossos (frontend)

knossos is the Nuxt.js frontend. While you're able to use Docker here, you may find it faster to just install npm and run the standard commands from there:

npm install
npm run dev

Once that's done, you'll be serving knossos on localhost:3000 with hot reloading. You can replace the dev in npm run dev with build to build for a production server and start to start the server. You can also use npm run lint to find any eslint problems, and npm run fix to try automatically fixing those problems.

theseus (launcher), daedalus (metadata host), minos (authentication provider), and ariadne (analytics system)

These Rust programs are still in early development. Before attempting to contribute, ask for info in Discord.

minotaur (Gradle plugin)

Minotaur is the Gradle plugin used to automatically publish artifacts to Modrinth. To run your copy of the plugin in a project, publish it to your local Maven with ./gradlew publishToMavenLocal and add mavenLocal() to your buildscript.

Minotaur contains two test environments within it - one with ForgeGradle and one with Fabric Loom. You may tweak with these environments to test whatever you may be trying; just make sure that the modrinth task within each still functions properly. GitHub Actions will validate this if you're making a pull request, so you may want to use act pull_request to test them locally.


The documentation (which you are reading right now!) is the place to find any and all general information about Modrinth and its API. The instructions are largely the same as knossos, except for the lint commands.