railties provides the core Rails internals including handling application bootup, plugins, generators, and Rake tasks.

Shellany is a Ruby library providing functions to capture the output produced by running shell commands.

GlobalID provides a way to generate URIs from a model in Ruby that uniquely identify it.

Nokogiri (鋸) parses and searches XML/HTML, and features both CSS3 selector and XPath 1.0 support.

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

Capybara is an integration testing tool for rack based web applications. It simulates how a user would interact with a website.

fog is a Ruby cloud services library. This package provides shared classes and tests for fog providers and services.

This package extends the String class and adds a ColorizedString with methods to set text color, background color, and text effects.

This package provides a Partial native implementation of the liquid ruby gem in C that makes it operate about three times faster.

Like a modern code version of the mythical beast with 100 serpent heads, Typhoeus runs HTTP requests in parallel while cleanly encapsulating handling logic.

This module provides a String#unindent Ruby method to unindent strings, which can be useful to unindent multiline strings embedded in already-indented code.

Cucumber is a tool for running automated tests written in plain language. It's designed to support a Behaviour Driven Development (BDD) software development workflow.

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality. The protocol is described in IMAP.

This package containse the JSON parsing tools shared between a number of providers in the fog gem. fog is a Ruby cloud services library.

Ruby Bindings for the GNU LibIDN library, an implementation of the Stringprep, Punycode and IDNA specifications. These are used to encode and decode internationalized domain + names according to the IDNA2003 specifications.

Included are the most important parts of the Stringprep, Punycode and IDNA APIs like performing Stringprep processings, encoding to and decoding from Punycode strings and converting entire domain names to and from the ACE encoded form.

Bio::Kseq provides ruby bindings to the kseq.h FASTA and FASTQ parsing code. It provides a fast iterator over sequences and their quality scores.

This package allows you to test FTP implementations in ruby. It is a minimal single-client FTP server that can be bound to any arbitrary port on localhost.

Zeitwerk implements constant autoloading with Ruby semantics. Each gem and application may have their own independent autoloader, with its own configuration, inflector, and logger. Supports autoloading, reloading, and eager loading.

HighLine provides a high-level IO library that provides validation, type conversion, and more for command-line interfaces. HighLine also includes a menu system for providing multiple options to the user.

The Polyglot library allows a Ruby module to register a loader for the file type associated with a filename extension, and it augments require to find and load matching files.

Maxitest is a wrapper around Minitest with extra functionality such as timeouts, an mtest executable that can run tests by line number, support for interrupted tests, better backtraces, and more.

Sanitize is a whitelist-based HTML and CSS sanitizer. Given a list of acceptable elements, attributes, and CSS properties, Sanitize will remove all unacceptable HTML and/or CSS from a string.

Data URIs allow resources to be embedded inside a URI. The URI::Data class provides support for parsing these URIs using the normal URI.parse method.

This library provides functionality to send Internet mail via SMTP, the Simple Mail Transfer Protocol. The SMTP protocol specification is known as RFC2821.