Redis is an in-memory database that persists on disk. The data model is key-value, but many different kind of values are supported: Strings, Lists, Sets, Sorted Sets, Hashes, HyperLogLogs, Bitmaps.

libgit2 is a portable, pure C implementation of the Git core methods provided as a re-entrant linkable library with a solid API, allowing you to write native speed custom Git applications in any language with bindings.

Rugged is a library for accessing libgit2 in Ruby. It gives you the speed and portability of libgit2 with the beauty of the Ruby language.

bcrypt-ruby is a Ruby binding for the OpenBSD bcrypt() password hashing algorithm, allowing you to easily store a secure hash of your users' passwords.

MySQL Server, the world's most popular open source database, and MySQL Cluster, a real-time, open source transactional database.

Hubot is more than just a chat robot, he’s essential to the way we work at GitHub. Whether it’s putting moustaches on images, printing real-world objects for us, or deploying the production code for what you see before you now, Hubot is an indispensable member our team—even if he occasionally loses his brain. View Hubot’s site

Zepto is a minimalist JavaScript library for modern browsers with a largely jQuery-compatible API. If you use jQuery, you already know how to use Zepto. We use Zepto to keep the performance of our mobile web experience nice and snappy.

Open Source, Distributed, RESTful Search Engine

pushState + ajax = pjax

D3.js is a JavaScript library for manipulating documents based on data that powers the graphs and charts throughout GitHub. D3 helps you bring data to life using HTML, SVG and CSS. D3’s emphasis on web standards gives you the full capabilities of modern browsers without tying yourself to a proprietary framework, combining powerful visualization components and a data-driven approach to DOM manipulation.

Plax is a jQuery plugin that makes it suuuuuper easy to parallax elements in your site based on mouse position. You can see it implemented in many places throughout GitHub, including the 404 page and the 500 page.

Ace is a standalone code editor written in JavaScript. Its goal is to create a browser based editor that matches and extends the features, usability and performance of existing native editors such as TextMate, Vim or Eclipse. It can be easily embedded in any web page or JavaScript application, and we use it to power the web-based editing workflow here on GitHub. For demos and more information, check out the Ace website.

The ZeroClipboard library provides an easy way to copy text to the clipboard using an invisible Adobe Flash movie and a JavaScript interface. The "Zero" signifies that the library is invisible and the user interface is left entirely up to you.

Moment.js keeps our frontend clocks runnings

A frontend asset package manager

Language Savant. If your repository's language is being reported incorrectly, send us a pull request!

Rails is a web-application framework that includes everything needed to create database-backed web applications according to the Model-View-Controller (MVC) pattern.

Ever wondered how to get emoji, syntax highlighting, custom linking, input sanitization, and markdown to play nice together? We've extracted several of the HTML utilities that we use internally in GitHub and packaged them into a gem for your enjoyment. This module includes a small framework for defining DOM based content filters and applying them to user provided content. Read an introduction about this project in this blog post.

Emoji is a mission critical part of our culture here at GitHub, and with this project, you can bring emoji into your life too!

Jekyll is a simple, blog-aware, static site generator perfect for personal, project, or organization sites. Think of it like a file-based CMS, without all the complexity. Jekyll is the engine behind GitHub Pages, which you can use to host sites right from your GitHub repositories. Read more on the Jekyll website.

Octokit is a Ruby toolkit for the GitHub API. Not into Ruby? There are also versions of Octokit for Objective-C, .NET, and Go. Read more on the Octokit website

Charlock Holmes provides character encoding detection as well as more robust transcoding so we can do our best to make sure we render your data as UTF-8.

Server automation framework and application

Used by Enterprise! Resque is a Redis-backed Ruby library for controlling background jobs.

Identify email addresses or domains names that belong to colleges or universities. Help automate the process of approving or rejecting academic discounts.

nanoc is a web publishing system written in Ruby. We use nanoc to power the GitHub Developer site.

Ephemeral Docker jails for running untrusted Ruby code

Test your rendered HTML files to make sure they're accurate.