About the Gemified Standard Library
Ruby's standard library is in the process of being gemified. It will soon - Ruby 2.5 - consist of RubyGems, which can be updated independently from Ruby. Some standard libraries have already be turned into gems before Ruby 2.5.
There are two different kinds of standard gems:
Default gems: These gems are part of Ruby and you can always require them directly. You cannot remove them. They are maintained by Ruby core.
Bundled gems: The behavior of bundled gems is similar to normal gems, but they get automatically installed when you install Ruby. They can be uninstalled and they are maintained outside of Ruby core.
Standard Gems Version Data
Every Ruby version ships a specific set of default and bundled gems. The tables below list included gems of the current Ruby version 2.4.2. There is also version matrix, a table which describes which Ruby version comes with which gem versions. The raw data is available as default_gems.json and bundled_gems.json.
Default Gems (Ruby 2.4.2)
|bigdecimal c||1.3.0||Support for arbitrary-precision floating point decimal arithmetic||RubyGems, GitHub, MRI, RDoc|
||RubyGems, GitHub, MRI, RDoc|
|openssl c||2.0.5||Wraps OpenSSL for cryptographic functionality||RubyGems, GitHub, MRI, RDoc|
|psych c||2.2.2||Support for YAML (YAML Ain't Markup Language)||RubyGems, GitHub, MRI, RDoc|
|rdoc||5.0.0||Ruby documentation generator||RubyGems, GitHub, MRI (1), MRI (2), RDoc|
Bundled Gems (Ruby 2.4.2)
|did_you_mean||1.1.0||Patches error messages to suggest correct spelling of methods/classes/variables||RubyGems, GitHub|
|minitest||5.10.1||Test/spec framework, comes with mocking and benchmark capabilities||RubyGems, GitHub|
|net-telnet||0.1.1||Support for Telnet||RubyGems, GitHub|
|power_assert||0.4.1||Debug tool that displays intermediate results of a method chain||RubyGems, GitHub|
|rake||12.0.0||A Ruby task runner, inspired by make||RubyGems, GitHub|
|test-unit||3.2.3||A xUnit family unit testing framework||RubyGems, GitHub|
|xmlrpc||0.2.1||Remote Procedure Calls via XML and HTTP||RubyGems, GitHub|
Gems per Ruby Version
- Gem list for Ruby: 2.5.0
- Gem list for Ruby: 2.4.2 - 2.4.1 - 2.4.0
- Gem list for Ruby: 2.3.5 - 2.3.4 - 2.3.3 - 2.3.2 - 2.3.1 - 2.3.0
- Gem list for Ruby: 2.2.8 - 2.2.7 - 2.2.6 - 2.2.5 - 2.2.4 - 2.2.3 - 2.2.2 - 2.2.1 - 2.2.0