ActiveSupport is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. It includes support for multibyte strings, internationalization, time zones, and testing.

Compose, deliver, receive, and test emails using the controller/view pattern. Including support for multipart email and attachments.

This library integrates the SASS stylesheet language into Ruby on Rails.

ActionMailbox receives and processes incoming emails in Rails applications.

The ammeter gem makes it easy to write specs for Rails generators. An existing user is rspec-rails, which uses ammeter to spec its own generators.

ActionText edits and displays rich text in Rails applications.

ActionPack provides conventions for building and testing MVC web applications. These work with any Rack-compatible server.

marcel provides MIME type detection using magic numbers, filenames, and extensions

Action Cable integrates WebSockets with Rails applications. Through WebSockets it allows for real-time features in web applications.

Active Record connects classes to relational database table to establish an almost zero-configuration persistence layer for applications.

ActiveJob allows declaring job classes in a common way across Rails applications.

This package provides a toolkit for building modeling frameworks like Active Record. ActiveSupport handles attributes, callbacks, validations, serialization, internationalization, and testing.

ActionView provides conventions and helpers for building web pages in Ruby.

This gem can compare HTML and assert certain elements exists. This is useful when writing tests.

Ruby on Rails is a full-stack web framework optimized for programmer happiness and sustainable productivity. It encourages beautiful code by favoring convention over configuration.

Spring is a Ruby on Rails application preloader. It speeds up development by keeping your application running in the background so the application does need to boot it every time you run a test, rake task or migration.

Turbo aims to be as fast as single-page web application without having to write any JavaScript. Turbo accelerates links and form submissions without requiring server-side changes to the generated HTML. It allows carving up a page into independent frames, which can be lazy-loaded and operated as independent components. Finally, it helps making partial page updates using just HTML and a set of CRUD-like container tags. These three techniques reduce the amount of custom JavaScript that many web applications need to write by an order of magnitude. And for the few dynamic bits that are left, Stimulus can be used.

This package allows you to create an interactive Ruby session in your browser. Those sessions are launched automatically in case of an error and can also be launched manually in any page.

Bootsnap is a library that plugs into Ruby, with optional support for YAML, to optimize and cache expensive computations.

Sprockets is a Rack-based asset packaging system that concatenates and serves JavaScript, CoffeeScript, CSS, LESS, Sass, and SCSS.

The With advisory lock gem adds advisory locking to ActiveRecord for PostgreSQL and MySQL. SQLite is also supported, but this uses the file system for locks.

This gem provides Ruby and Ruby on Rails integration with Autoprefixer, which can parse CSS and add vendor prefixes to CSS rules using values from the Can I Use website.

This gem is used to handle HTML sanitization in Rails applications. If you need similar functionality in non Rails apps consider using Loofah directly.

This Ruby library integrates SassC-Ruby into Rails.