Some open-source projects provide mirrors on GitHub.com in addition to their official repositories, which are hosted elsewhere.

Here are a few prominent repositories that are mirrored on GitHub.com:

To set up your own mirror, you can configure a post-receive hook on your official project repository to automatically push commits to a mirror repository on GitHub.com (or GitHub Enterprise).

You can search repositories based on whether they're a mirror. To learn more, see "Searching repositories."