Development

Overview

Before starting local development, read the CONTRIBUTING guide to understand what changes are desirable and what general processes to use. You should also read the project's AI Contribution Policy to understand how we approach AI-assisted contributions.

Environments

The following instructions will guide you through the process of setting up a local development instance of Mastodon on your computer.

There are instructions for these environments:

• macOS
• Linux
• Docker
• Dev Containers
• GitHub Codespaces

Once completed, continue with the Next steps section below.

macOS

To set up macOS for native development, complete the following steps:

• Install Homebrew and run: brew install postgresql@14 redis libidn nvm vips to install the required project dependencies

• Use a Ruby version manager to activate the ruby in .ruby-version and run nvm use to activate the node version from .nvmrc

• Start the database services by running brew services start postgresql and brew services start redis

• Run RAILS_ENV=development bin/setup, which will install the required ruby gems and node packages and prepare the database for local development

  (Note: If you are on Apple Silicon and get an error related to libidn, you should be able to fix this by running gem install idn-ruby -- --with-idn-dir=$(brew --prefix libidn), then re-running the command above.)

• Finally, run the bin/dev script which will launch services via overmind (if installed) or foreman

Linux

The Mastodon documentation has a guide on installing Mastodon from source on Linux.

Docker

For production hosting and deployment with Docker, use the Dockerfile and docker-compose.yml in the project root directory.

For local development, install and launch Docker, and run:

docker compose -f .devcontainer/compose.yaml up -d
docker compose -f .devcontainer/compose.yaml exec app bin/setup
docker compose -f .devcontainer/compose.yaml exec app bin/dev

Dev Containers

Within IDEs that support the Development Containers specification, start the "Mastodon on local machine" container from the editor. The necessary docker compose commands to build and setup the container should run automatically. For Visual Studio Code this requires installing the Dev Container extension.

GitHub Codespaces

GitHub Codespaces provides a web-based version of VS Code and a cloud hosted development environment configured with the software needed for this project.

• Click the button to create a new codespace, and confirm the options
• Wait for the environment to build (takes a few minutes)
• When the editor is ready, run bin/dev in the terminal
• Wait for an Open in Browser prompt. This will open Mastodon
• On the Ports tab "stream" setting change Port visibility → Public

Next steps

• Once you have successfully set up a development environment, it will be available on http://localhost:3000
• Log in as the default admin user with the username admin@mastodon.local or admin@localhost (depending on your setup) and the password mastodonadmin.
• Check out the Mastodon docs for tips on working with emails in development (you'll need this when creating new user accounts) as well as a list of useful commands for testing and updating your dev instance.
• You can optionally populate your database with sample data by running bin/rails dev:populate_sample_data. This will create a @showcase_account account with various types of contents.