What is GitHub?
The dominant hosting platform for Git repositories, with collaboration and CI tooling built on top.
Definition
GitHub wraps Git hosting in the social and process layer that made distributed version control practical for teams: pull requests for proposing and reviewing changes, issues for tracking work, and branch protection rules for enforcing review and CI status before merge. GitHub Actions provides CI/CD triggered by repository events, running on hosted or self-hosted runners. Acquired by Microsoft in 2018, it hosts the overwhelming majority of open-source work, which makes a project's GitHub presence—commit recency, issue response times, maintainer count—the standard proxy for whether a dependency is alive. GitHub Copilot brought AI code completion to the mainstream, and the platform now layers security tooling (Dependabot, secret scanning, CodeQL) into the same workflow.