This validator uses a strict YAML 1.2 parser and treats parser diagnostics as failures, including duplicate map keys and unresolved aliases. The preview is intentionally secondary: use it to inspect valid YAML, not as a replacement for a dedicated formatter.
Private browser utility / Developer
Free YAML Validator
Runs entirely in your browser - no upload, no sign-up.
Runs in your browser - nothing is uploaded.
YAML
Valid YAML preview
Paste YAML to validate it
What does a YAML validator do?
A YAML validator checks whether pasted YAML is valid before you save or deploy it. It parses the text live, reports the first syntax error with a line and column when available, and shows a normalized preview only after the document passes validation. Nothing is uploaded.
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How to use
- 01Paste YAML
Paste a YAML document or YAML stream into the input box.
- 02Read the status
The validator updates live and shows either Valid YAML or the first parser error.
- 03Use the location
When the parser exposes a position, jump to the reported line and column in your editor.
- 04Copy the preview
For valid YAML, copy the normalized preview or use the stats panel to review the document shape.
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Who it's for
- Developers checking Kubernetes, GitHub Actions, Docker Compose, OpenAPI or app config before committing a change.
- DevOps and SRE teams catching indentation mistakes, duplicate keys and broken anchors before a deployment.
- Support engineers validating YAML snippets from tickets without uploading private environment values.
- Technical writers testing examples that include comments, lists, mappings and multiline block strings.
FAQ
Is the YAML validator free?
Yes. The YAML validator is free to use, with no sign-up, no download and no usage limit. Paste YAML, read the validation result and copy the valid preview when you need it.
Is my YAML uploaded anywhere?
No. Validation happens locally in your browser. That is useful for deployment snippets, CI files, secrets templates and other configuration text you do not want to send to a server-side checker.
What errors can a YAML validator catch?
It can catch syntax problems such as broken indentation, missing colons, unterminated flow lists, duplicate map keys and aliases that reference a missing anchor. Parser wording can vary, but the status message shows the first diagnostic and location when available.
Does it validate multiple YAML documents?
Yes. YAML streams with document markers are parsed as multiple documents, and the stats panel reports the document count. If any document has a parser error, the whole input is marked invalid.
Is this also a YAML formatter?
It shows a normalized preview after validation, but the main job is syntax checking and diagnostics. Use the YAML formatter when you want indentation controls and a formatting-first workflow.
Why does valid-looking YAML fail?
YAML is whitespace-sensitive, so a single extra space can move a key into a different mapping or list. Strict parsers also reject duplicate keys and unresolved aliases because those cases make configuration files ambiguous or unusable.