GitHub Actions is the CI/CD automation layer built into GitHub. Workflows are YAML files stored in .github/workflows that respond to any GitHub event: push, pull request, issue, release, schedule, or manual workflow_dispatch trigger. Pipeline configuration is versioned in the repository alongside application code.
Hosted runners (Linux, Windows, macOS) execute jobs in isolated VMs provisioned per job. Larger runners (up to 64-core Linux) and ARM-native runners for Apple Silicon are available. Self-hosted runners connect to GitHub and accept jobs without inbound firewall rules.
OIDC federation generates short-lived cloud tokens for AWS, GCP, Azure, and HashiCorp Vault, eliminating the need to store long-lived credentials as repository secrets. Reusable workflows allow a workflow defined in one repository to be called from others in the organization. The Actions cache stores dependency artifacts between runs, keyed on lock file hashes. The marketplace includes 20,000+ pre-built actions. Pricing: free for public repositories; free minutes per month for private repositories, then per-minute billing.