Is my YAML data uploaded to a server?

No. Everything runs entirely in your browser with JavaScript. Nothing is sent over the network, which makes the tool safe for sensitive data.

Which YAML features are understood?

The full YAML 1.2 core schema, plus merge keys (<<: *base) used by Docker Compose and GitLab CI. Multi-document streams are validated as a single document.

What does the report contain?

The root type (mapping, sequence or scalar), the number of keys or items, and the document size — a quick sanity check before you commit a config.

YAML Validator — Check YAML Syntax Online for Free

Validate YAML syntax instantly in your browser with precise error positions. Free, private and offline-friendly: your data never leaves your device.

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YAML input

Result output

Why validate YAML?

YAML’s significant whitespace makes it easy to break a config with one wrong indent — and CI pipelines fail minutes later. Paste your YAML above to check it instantly.

How it works

The validator parses your YAML locally with a spec-compliant parser. Errors come back with the exact line and column; valid documents get a short report with the root type and size. Nothing is uploaded, so production configs with secrets are safe to check.

Frequently asked questions

Is my YAML data uploaded to a server?: No. Everything runs entirely in your browser with JavaScript. Nothing is sent over the network, which makes the tool safe for sensitive data.
Which YAML features are understood?: The full YAML 1.2 core schema, plus merge keys (<<: *base) used by Docker Compose and GitLab CI. Multi-document streams are validated as a single document.
What does the report contain?: The root type (mapping, sequence or scalar), the number of keys or items, and the document size — a quick sanity check before you commit a config.