YAML Preflight

About YAML Preflight

YAML Preflight is a browser-based tool for validating YAML files intended for use in GitHub Actions workflows. It checks for issues that pass standard YAML parsing but cause problems in GitHub Actions specifically, including invalid Actions permissions values, strict syntax errors, and duplicate keys. Parsing and validation run entirely client-side, with no upload, signup, checkout, or payment required to use the tool.

The tool accepts pasted YAML up to 100 KB and displays a parsed preview alongside any findings. It includes preset examples demonstrating specific error types: invalid Actions permissions, duplicate keys, missing dashes, and unquoted colons. It is aimed at developers who want to catch workflow-breaking YAML errors before committing changes that could cause a GitHub Actions workflow to fail silently.

The page also proposes a paid follow-on feature, a monitor that would check repository YAML changes and report problems before merge, priced at $9/month. This feature is not built; a button on the page records anonymous interest in it without collecting payment. The product is built by aevumere.

Key features

• Validates YAML syntax and flags strict parsing errors like duplicate keys and missing dashes
• Checks GitHub Actions permissions blocks against valid permission scopes
• Detects unquoted-colon and other common YAML formatting mistakes
• Runs entirely client-side in the browser with no upload, signup, or payment required
• Shows a parsed YAML preview after validation

Frequently asked questions