YAML Lint Online

Lint YAML files for syntax errors and style issues — catch problems before deployment

What Is YAML Linting?

YAML linting goes beyond basic validation by checking not only for syntax errors but also for style issues, best practices, and potential problems that are technically valid YAML but likely indicate mistakes. A YAML linter detects inconsistent indentation, duplicate keys (which silently overwrite earlier values), very long lines, truthy string values that might be unintended (yes/no becoming booleans), trailing spaces, and missing document-end markers.

YAML linting is especially valuable for infrastructure-as-code workflows where configuration errors can have serious consequences. A duplicate key in a Kubernetes manifest silently uses the last value, which may not be the one you intended. A YAML boolean that you meant as a string (like country: NO becoming false) causes subtle bugs. Linting catches these issues before they reach production, saving hours of debugging time and preventing configuration-related outages.

How to Lint YAML Files Online

1. Paste your YAML content into the editor — the linter analyzes it automatically
2. Review the diagnostics panel: errors (red), warnings (yellow), and style notes (blue)
3. Click any diagnostic to jump to the exact line and column in the editor
4. Fix issues starting with errors, then warnings, then style improvements
5. Re-lint after changes to confirm all issues are resolved before deployment

Why Use PinusX YAML Linter?

PinusX lints your YAML with 100% client-side processing. Your Docker Compose files, Kubernetes manifests, GitHub Actions workflows, and infrastructure configurations never leave your browser. These files contain deployment details, service configurations, and sometimes credential references that should not be exposed to third-party servers. In November 2025, jsonformatter.org leaked over 80,000 user credentials from server-side processing. PinusX runs the entire linting engine locally in your browser tab, ensuring your infrastructure configs remain on your device.

Frequently Asked Questions

What is the difference between YAML lint and YAML validate?

Validation checks if YAML is syntactically parseable — does it follow the YAML spec? Linting includes validation plus style and best-practice checks: duplicate keys, truthy string warnings, line length limits, consistent quoting, and indentation consistency. Linting catches more potential issues than validation alone.

Why does the linter warn about yes/no values?

In YAML, bare yes, no, on, off, true, and false are parsed as boolean values, not strings. If you write country: NO, YAML parses it as country: false. The linter warns about this common gotcha. To use these words as strings, quote them: country: 'NO'. This is one of YAML's most frequent pitfalls.

Does it check for duplicate keys?

Yes. Duplicate keys in the same YAML mapping are technically allowed by the spec but the last value silently overwrites earlier ones. This is almost always a mistake. The linter flags duplicate keys as warnings since they indicate copy-paste errors or unintended overwrites that can cause configuration bugs.

Can I configure linting rules?

The linter applies a sensible set of default rules suitable for most YAML use cases. Common rules include: max line length, required document start marker (---), indentation size, truthy value warnings, and duplicate key detection. These rules align with yamllint's default configuration, the most popular YAML linting tool.

Your data never leaves your browser. 100% client-side processing.