This GitHub Content Attachments service allows a GitHub Application to provide more information in GitHub for URLs that link to registered domains. GitHub renders the information provided by the app under the URL in the body or comment of an issue or pull request. The Content Attachments API is currently in beta and available for use with GitHub Applications only. It provides GitHub Apps with the ability to listen for links in issues and pull requests and attach content to those links. GitHub is a web service that provides a way to use the Hello World guide, to create a repository, start a branch, write comments, and open a pull request.