The GitHub Git repository hosting platform experienced a widespread and major services outage. Issues, PRs, Dashboard, Projects, and Notifications features were affected. GitHub’s engineering team resolved the issue after 20 minutes, however, they did not mention in the incident report what was the cause behind this widespread outage. Users have also reported on Twitter during the last hour that they are experiencing various types of issues, ranging from the entire site being down to 500 Internal Server Error status codes and pull requests not working.
Source: https://www.bleepingcomputer.com/news/technology/github-experienced-widespread-major-services-outage/