JavaScript library and newly introduced CoffeeScript and Sass into the stack. Rails 3.2 was released on January 20, 2012 with a faster development mode and routing engine (also known as Journey engine), Automatic Query Explain and Tagged Logging. Rails 3.2.x is the last version that supports Ruby 1.8.7. Rails 3.2.12 supports Ruby 2.0. Rails 4.0 was released on June 25, 2013, introducing Russian Doll Caching, Turbolinks, Live Streaming as well as making Active Resource, Active Record Observer and other components optional by splitting them as gems. Rails 4.1 was released on April 8, 2014, introducing Spring, Variants, Enums, Mailer previews, and secrets.yml. Rails 4.2 was released on December 19, 2014, introducing Active Job, asynchronous emails, Adequate Record, Web Console, and foreign keys. Rails 5.0 was released on June 30, 2016, introducing Action Cable, API mode, and Turbolinks 5. Rails 5.0.0.1 was released on August 10, 2016, with Exclusive use of rails CLI over Rake and support for Ruby version 2.2.2 and above. Rails 5.1 was released on April 27, 2017, introducing JavaScript integration changes (management of JavaScript dependencies from NPM via Yarn, optional compilation of JavaScript using Webpack, and a rewrite of Rails UJS to use vanilla JavaScript instead of depending on jQuery), system tests using Capybara, encrypted secrets, parameterized mailers, direct & resolved routes, and a unified form_with helper replacing the form_tag/form_for helpers. Rails 5.2 was released on April 9, 2018, introducing new features that include ActiveStorage, built-in Redis Cache Store, updated Rails Credentials and a new DSL that allows for configuring a Content Security Policy for an application. Rails 5.2.2 was released on December 4, 2018, introducing numerous bug fixes and several logic improvements. Rails 6.0 was released on August 16, 2019, making Webpack default, adding mailbox routing, a default online rich-text editor, parallel testing, multiple database support, mailer routing and a new autoloader. Rails 6.1 was released on December 9, 2020, adding per-database connection switching, horizontal database sharding, eager loading of all associations, Delegated Types as an alternative to single-table inheritance, asynchronous deletion of associations, error objects, and other improvements and bug fixes. Rails 7.0 was released on December 15, 2021, replacing Node.js and Webpack with import maps for JavaScript management by default, replacing Turbolinks with a combination of Turbo and Stimulus, adding at-work encryption into Active Record, using Zeitwerk exclusively for code loading, and more. Technical overview Ruby on Rails evolves radically from release to release