GitHub Actions Workflows

GitHub Actions is a CI/CD platform integrated directly into GitHub that allows defining automated workflows in YAML files stored in the .github/workflows directory. Workflows are triggered by GitHub events (push, pull_request, release, schedule, workflow_dispatch) and consist of one or more jobs that run on GitHub-hosted or self-hosted runners. Each job contains a sequence of steps that execute shell commands or reusable actions.

Key features include matrix strategies for testing across multiple OS and runtime versions, service containers for integration testing (e.g., spinning up PostgreSQL alongside tests), caching with actions/cache for node_modules and build artifacts, and environment protection rules with required reviewers for production deployments. Reusable workflows and composite actions enable DRY pipeline definitions across repositories in an organization.

GitHub Actions supports OIDC-based authentication for cloud deployments (eliminating long-lived credentials), environment-scoped secrets, concurrency groups to cancel superseded runs, and artifact upload/download for sharing build outputs between jobs. The marketplace provides thousands of community actions, though security best practices dictate pinning actions to specific SHA commits rather than mutable tags to prevent supply chain attacks.