Start Here
Getting Started with Rails
Everything you need to know to install Rails and create your first application.
Models
Active Record Query Interface
Instead of using raw SQL to find database records, Active Record provides better ways to carry out the same operations. This guide covers different ways to retrieve data from the database using Active Record.
Active Record Migrations
Migrations are a feature of Active Record that allows you to evolve your database schema over time. Rather than write schema modifications in pure SQL, migrations allow you to use a Ruby DSL to describe changes to your tables.
Active Record Basics
Active Record allows your models to interact with the application's database. This guide will get you started with Active Record models and persistence to the database.
Active Record Associations
In Active Record, an association is a connection between two Active Record models. This guide covers all the associations provided by Active Record.
Active Record Validations
Validations are used to ensure that only valid data is saved into your database. This guide teaches you how to validate the state of objects before they go into the database, using Active Record's validations feature.
Active Record Callbacks
Callbacks make it possible to write code that will run whenever an object is created, updated, destroyed, etc. This guide teaches you how to hook into this object life cycle of Active Record objects.
Active Model Basics
Active Model allows you to create plain Ruby objects that integrate with Action Pack, but don't need Active Record for database persistence. Active Model also helps build custom ORMs for use outside of the Rails framework. This guide provides you with all you need to get started using Active Model classes.
Views
Action View Helpers
Action View has helpers for handling everything from formatting dates and linking to images, to sanitizing and localizing content. This guide introduces a few of the more common Action View helpers.
Layouts and Rendering in Rails
This guide covers the basic layout features of Action Controller and Action View, including rendering and redirecting, using content_for blocks, and working with partials.
Action View Form Helpers
HTML forms can quickly become tedious to write and maintain because of the need to handle form control naming and its numerous attributes. Rails does away with this complexity by providing view helpers for generating form markup.
Action View Overview
Action View is responsible for generating the HTML for web responses. This guide provides an introduction to Action View.
Controllers
Rails Routing from the Outside In
The Rails router recognizes URLs and dispatches them to a controller's action. This guide covers the user-facing features of Rails routing. If you want to understand how to use routing in your own Rails applications, start here.
Action Controller Overview
Action Controllers are the core of a web request in Rails. This guide covers how controllers work and how they fit into the request cycle of your application. It includes sessions, filters, cookies, data streaming, and dealing with exceptions raised by a request, among other topics.
Other Components
Action Text Overview
This guide describes how to use Action Text to handle rich text content.
Webpacker
This guide will show you how to install and use Webpacker to package JavaScript, CSS, and other assets for the client-side of your Rails application.
Action Mailbox Basics
This guide describes how to use Action Mailbox to receive emails.
Active Storage Overview
Active Storage facilitates uploading files to a cloud storage service, transforming uploads and extracting metadata. This guide covers how to attach files to your Active Record models.
Active Job Basics
Active Job is a framework for declaring background jobs and making them run on a variety of queuing backends. This guide provides you with all you need to get started creating, enqueuing, and executing background jobs.
Action Mailer Basics
This guide provides you with all you need to get started in sending emails from your application, and many internals of Action Mailer.
Action Cable Overview
Action Cable integrates WebSockets with the rest of your Rails application. It allows for real-time features to be written in Ruby in the same style and form as the rest of your Rails application. This guide explains how Action Cable works, and how to use WebSockets to create real-time features.
Active Support Core Extensions
Active Support provides Ruby language extensions and utilities. It enriches the Ruby language for the development of Rails applications, and for the development of Ruby on Rails itself.
Digging Deeper
Debugging Rails Applications
This guide describes how to debug Rails applications. It covers the different ways of achieving this and how to understand what is happening "behind the scenes" of your code.
Active Record and PostgreSQL
This guide covers PostgreSQL specific usage of Active Record.
Caching with Rails: An Overview
This guide is an introduction to speeding up your Rails application with caching.
Classic to Zeitwerk HOWTO
This guide documents how to migrate Rails applications from `classic` to `zeitwerk` mode.
Securing Rails Applications
This guide describes common security problems in web applications and how to avoid them with Rails.
The Rails Initialization Process
This guide explains the internals of the initialization process in Rails. It is an extremely in-depth guide and recommended for advanced Rails developers.
Working with JavaScript in Rails
This guide explains how to use import maps or jsbundling-rails to include JavaScript in Rails applications, and covers the basics of working with Turbo in Rails.
Testing Rails Applications
This is a rather comprehensive guide to the various testing facilities in Rails. It covers everything from 'What is a test?' to Integration Testing. Enjoy.
Using Rails for API-only Applications
This guide explains how to effectively use Rails to develop a JSON API application.
Multiple Databases with Active Record
This guide covers using multiple databases in your application.
Autoloading and Reloading Constants
This guide documents how autoloading and reloading constants work (Zeitwerk mode).
The Asset Pipeline
The asset pipeline provides a framework to concatenate and minify or compress JavaScript, CSS and image assets. It also adds the ability to write these assets in other languages and pre-processors such as CoffeeScript, Sass, and ERB.
Active Record Encryption
This guide covers encrypting your database information using Active Record.
The Rails Command Line
There are a few commands that are absolutely critical to your everyday usage of Rails. This guide covers the command line tools provided by Rails.
Rails Internationalization (I18n) API
This guide covers how to add internationalization to your applications. Your application will be able to translate content to different languages, change pluralization rules, use correct date formats for each country, and so on.
Active Support Instrumentation
This guide explains how to use the instrumentation API inside of Active Support to measure events inside of Rails and other Ruby code.
Error Reporting in Rails Applications
This guide introduces ways to manage exceptions that occur in Ruby on Rails applications.
Configuring Rails Applications
This guide covers the basic configuration settings for a Rails application.
Extending Rails
Rails on Rack
This guide covers Rails integration with Rack and interfacing with other Rack components.
Getting Started with Engines
Engines can be considered miniature applications that provide additional functionality to their host applications. In this guide you will learn how to create your own engine and integrate it with a host application.
Creating and Customizing Rails Generators & Templates
This guide covers the process of adding a brand new generator to your extension or providing an alternative to an element of a built-in Rails generator (such as providing alternative test stubs for the scaffold generator).
The Basics of Creating Rails Plugins
This guide covers how to build a plugin to extend the functionality of Rails.
Threading and Code Execution in Rails
This guide describes the considerations needed and tools available when working directly with concurrency in a Rails application.
Contributing
Contributing to Ruby on Rails
Rails is not "someone else's framework". This guide covers a variety of ways that you can get involved in the ongoing development of Rails.
API Documentation Guidelines
This guide documents the Ruby on Rails API documentation guidelines.
Guides Guidelines
This guide documents the Ruby on Rails guides guidelines.
Policies
Maintenance Policy
What versions of Ruby on Rails are currently supported, and when to expect new versions.
Release Notes
Version 6.0 - August 2019
Release notes for Rails 6.0.
Version 4.2 - December 2014
Release notes for Rails 4.2.
Version 7.1 - ?
Release notes for Rails 7.1.
Version 5.0 - June 2016
Release notes for Rails 5.0.
Version 3.1 - August 2011
Release notes for Rails 3.1.
Version 5.2 - April 2018
Release notes for Rails 5.2.
Version 2.2 - November 2008
Release notes for Rails 2.2.
Version 4.0 - June 2013
Release notes for Rails 4.0.
Version 7.0 - December 2021
Release notes for Rails 7.0.
Version 5.1 - April 2017
Release notes for Rails 5.1.
Version 2.3 - March 2009
Release notes for Rails 2.3.
Version 3.0 - August 2010
Release notes for Rails 3.0.
Version 4.1 - April 2014
Release notes for Rails 4.1.
Version 6.1 - December 2020
Release notes for Rails 6.1.
Version 3.2 - January 2012
Release notes for Rails 3.2.
Upgrading Ruby on Rails
This guide provides steps to be followed when you upgrade your applications to a newer version of Ruby on Rails.