What is the GitLab CI Lint tool and how do you validate a.gitlab-ci.yml file?

Before committing a .gitlab-ci.yml change and waiting for a pipeline to run, you can validate the configuration using GitLab's built-in CI Lint tool. This catches syntax errors, invalid keywords, and configuration issues immediately.

# Method 1: GitLab UI
# Navigate to: Build > Pipelines > then click "CI Lint"
# or: Project > CI/CD > Lint (path varies by GitLab version)
# Paste your YAML and click "Validate"

# Method 2: Pipeline Editor
# Navigate to: Build > Pipeline editor
# The editor validates in real-time as you type

# Method 3: GitLab API
curl --header "PRIVATE-TOKEN: <your-token>" \
     --header "Content-Type: application/json" \
     --data '{"content": "include:\n  - local: /.gitlab-ci.yml"}' \
     "https://gitlab.example.com/api/v4/projects/:id/ci/lint"

# Method 4: gitlab-ci-local (third-party tool)
# Run pipelines locally for development:
pip install gitlab-ci-local  # or: brew install gitlab-ci-local
gitlab-ci-local              # simulates pipeline execution locally

# The CI Lint tool checks:
# - Valid YAML syntax
# - Valid GitLab CI keywords
# - Correct job structure
# - Variable expansion
# - Stage references are defined

Pipeline editor: GitLab's built-in pipeline editor (Build > Pipeline editor) provides real-time validation, syntax highlighting, a visual pipeline diagram, and the CI Lint tool in one interface. It is the recommended way to edit .gitlab-ci.yml files in the browser.

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