What does this tool validate?

The tool first checks that your file is syntactically valid YAML. If it is, it then runs platform-specific structural checks: for GitHub Actions it verifies that on, jobs, runs-on, and steps are present; for GitLab CI it checks for at least one job with a script key; for Generic YAML it checks for duplicate keys and excessive nesting.

What is the difference between Error, Warning, and Info?

An Error means the workflow is likely broken and will fail to run. A Warning indicates a best-practice violation that may cause unexpected behaviour. Info is an informational notice about style or potential improvements that do not affect execution.

Does the validator run my workflow?

No. Validation is entirely static and runs in your browser. No code is executed and no files are sent to any server. The tool only parses and inspects the YAML structure using the js-yaml library.

Why does my GitHub Actions workflow show an error about on?

Every GitHub Actions workflow file must contain an on key that defines the trigger events, such as push, pull_request, or schedule. Without it, GitHub cannot determine when to run the workflow and will reject the file.

Can I validate generic YAML files that are not CI/CD configs?

Yes. Select Generic YAML from the platform dropdown. The tool will check for basic YAML syntax errors, duplicate keys which can cause unexpected overrides, and deeply nested structures that may indicate configuration complexity issues.

CI/CD YAML Validator

Validate GitHub Actions workflows, GitLab CI pipelines, or any YAML file online. Get instant feedback on syntax errors, missing required keys, and structural warnings.

YAML Content

Frequently Asked Questions

CI/CD YAML Validator – GitHub Actions & GitLab CI Linter Online | CoreTools