GitHub Actions Runner

GitHub Actions Runner is the free and open-source application that executes workflows on a machine (self-hosted or GitHub-hosted) as part of GitHub Actions, the CI/CD platform integrated into the codebase. The runner application registers with GitHub, polls for jobs, executes workflow steps, and reports results back to GitHub. Key features: self-hosted runners: in addition to GitHub-hosted runners (Ubuntu, Windows, macOS VMs provided by GitHub), users can set up their own machines (physical, virtual, or cloud) as self-hosted runners. Self-hosted runners are useful for accessing private networks, running on custom hardware (GPUs, ARM), avoiding GitHub-hosted runner limits, and reducing costs for high-volume CI/CD. Runner registration: the runner is registered to a repository, organization, or enterprise using a registration token. Multiple runners can be grouped into runner groups with custom access policies and labels. Labels (e.g., self-hosted, linux, x64, gpu) allow workflows to target specific runners. Job execution: the runner receives a job (a set of steps) from GitHub Actions. Each step runs in the runner environment, executing actions (reusable units of code) or shell commands (bash, PowerShell, cmd). Steps can share data via outputs and environment variables. Workspaces and artifacts: each job runs in a dedicated workspace directory on the runner. The actions/checkout action clones the repository. Build artifacts can be uploaded and downloaded via actions/upload-artifact and actions/download-artifact. Caching: actions/cache for caching dependencies across runs. Docker container support: jobs can run inside Docker containers. Kubernetes: Actions Runner Controller (ARC) for deploying runners on Kubernetes at scale. Custom labels and routing. Cross-platform: Linux (x64, ARM64, ARM), Windows (x64), macOS (x64, ARM64/Apple Silicon). Auto-update. C#. MIT.