rails/rails

Dependencies

What each component requires at runtime, plus the dev/test stack.

Runtime dependencies (per gemspec)

The component gemspecs declare their hard runtime dependencies. These are the gems an application will install when it adds the component to its Gemfile.

activesupport

i18n (for translation)
tzinfo (time zone data)
concurrent-ruby (concurrency primitives)
connection_pool
minitest (because ActiveSupport::TestCase is built on it)
securerandom
useragent
benchmark
logger
base64
bigdecimal
drb
mutex_m

activerecord

activesupport, activemodel (same version)
timeout

actionpack

activesupport (same version)
actionview (same version)
nokogiri
racc
rack (>= 2.2.4, < 4)
rack-session
rack-test
rails-dom-testing
rails-html-sanitizer
useragent

actionview

activesupport (same version)
builder (XML builder)
erubi (ERB compiler)
rails-dom-testing
rails-html-sanitizer

actionmailer

actionpack, actionview, activejob, activesupport (same version)
mail (the SMTP / message DSL)
rails-dom-testing

actionmailbox

actionpack, activejob, activerecord, activestorage, activesupport (same version)
mail

activejob

activesupport (same version)
globalid (Active Record argument serialization)

actioncable

actionpack (same version)
activesupport (same version)
nio4r (event-driven IO)
websocket-driver
zeitwerk

activestorage

activerecord, activejob, actionpack, activesupport (same version)
marcel (MIME-type detection)

actiontext

actionpack, activerecord, activestorage, activesupport, globalid (same version)
nokogiri

railties

activesupport, actionpack (same version)
rackup
rake
thor
method_source
irb (for bin/rails console)
zeitwerk

rails (meta-gem)

All 12 components at the same version.
bundler (>= 1.15.0).

Dev / test dependencies

The top-level Gemfile adds tools used to develop on the framework:

Test framework: minitest, minitest-mock
System tests: capybara, selenium-webdriver
Browser & web server: puma, rack-cache
JavaScript / asset stacks (for testing integrations): sprockets-rails, propshaft, stimulus-rails, turbo-rails, jsbundling-rails, cssbundling-rails, importmap-rails, tailwindcss-rails, dartsass-rails
Solid stack (Rails 8 defaults): solid_cache, solid_queue, solid_cable
Deployment: kamal, thruster
Auth helpers (optional): bcrypt, argon2 (both require: false)
Misc: terser, json, uri, prism
Lint: rubocop, rubocop-minitest, rubocop-packaging, plus an in-repo rubocop-rails plugin
Releaser: releaser (path: tools/releaser)
Database adapters: sqlite3, mysql2, trilogy, pg (each declared in activerecord/Gemfile with conditional installation)
Cloud SDKs: aws-sdk-s3, google-cloud-storage, image_processing (in activestorage/Gemfile, optional)
Mail providers: various mail-* gems used in mailbox tests

The Gemfile.lock resolves to ~1,000 lines.

Active Record ships adapters for sqlite3, postgresql, mysql2, and trilogy. The corresponding gem (sqlite3, pg, mysql2, trilogy) must be in the host application's Gemfile. Active Record itself does not depend on any database driver.

JavaScript packages

A few components ship JS:

actioncable — published as @rails/actioncable on npm (actioncable/package.json).
activestorage — published as @rails/activestorage.
actiontext — published as @rails/actiontext.
actionview — ships UJS helpers via @rails/ujs (separate package).

Each component's package.json defines its own dependencies. The build is driven by Rollup (rollup.config.js).

Linting tools

RuboCop 1.79.2 (pinned in Gemfile).
Markdown lint via mdl with .mdlrc.rb.
ESLint for JavaScript via eslint.config.mjs.

Updating dependencies

Per-component gemspec changes are made in <component>/<component>.gemspec.
Top-level dev dependencies are in Gemfile.
Update Gemfile.lock via bundle update or bundle update <gem>.
New gem dependencies typically require a release-notes entry and a changelog mention.

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