CI and GitHub Actions Glossary

Plain-English definitions of the CI terms you meet in GitHub Actions, with examples.

• What Are CI Minutes? How Billing WorksCI minutes are the billed compute time your pipelines use. Learn how GitHub Actions counts minutes, multipliers, rounding and how to reduce usage.
• What Is a Cache Key in GitHub Actions?A cache key is the string that identifies a saved cache in GitHub Actions. Learn how keys and restore-keys work and how to avoid stale caches.
• What Is a Concurrency Group in GitHub Actions?A concurrency group makes GitHub Actions run one workflow or job at a time per key and can cancel older runs. See the YAML and common mistakes.
• What Is a Flaky Test? Definition and CausesA flaky test passes and fails on the same code without any change. Learn the common causes, how to detect them in CI and how to fix or quarantine them.
• What Is a Matrix Build in GitHub Actions?A matrix build runs one job many times with different inputs like OS or language version. Learn the syntax, include/exclude and common mistakes.
• What Is a Merge Queue in GitHub?A merge queue tests each pull request against the latest main plus the PRs ahead of it, so main never breaks from a bad merge. How it works.
• What Is a Remote Build Cache?A remote build cache stores task outputs from tools like Nx, Turborepo, Gradle and Bazel so CI and teammates skip work already done. How it works.
• What Is a Reusable Workflow in GitHub Actions?A reusable workflow is a GitHub Actions workflow other workflows can call with inputs and secrets. Learn workflow_call syntax and common mistakes.
• What Is a Runner in GitHub Actions?A GitHub Actions runner is the machine that executes a workflow job. Learn how runners are picked, the types available, and common mistakes.
• What Is a Self-Hosted Runner? (GitHub Actions)A self-hosted runner is a machine you control that runs GitHub Actions jobs. See how it works, the security risks, and when it is worth using.
• What Is an Artifact in GitHub Actions?A GitHub Actions artifact is a file or folder saved from a workflow run, such as a build or test report, to share between jobs or download later.
• What Is OIDC in GitHub Actions?OIDC lets GitHub Actions workflows get short-lived cloud credentials without stored secrets. See how it works, a YAML example and common mistakes.
• What Is Test Sharding in CI?Test sharding splits one test suite into slices that run in parallel on separate CI machines, cutting wall-clock time. How it works and common mistakes.
• What Is workflow_dispatch in GitHub Actions?workflow_dispatch is the GitHub Actions trigger that lets you start a workflow manually with inputs. Learn the syntax, CLI and API usage and pitfalls.