YAML Validator

A single misplaced space can break a Kubernetes manifest, a GitHub Actions workflow or a Docker Compose file, and the error from the tool that reads it is often cryptic. Paste the YAML here to find out whether it parses, and if not, see the exact line and column, the surrounding lines and a plain-English explanation. Valid files get a short summary: documents, keys, list items and nesting depth.

How to use this tool

1. Paste your YAML into the box; it is checked as you type.
2. If it is invalid, read the location and the explanation, and look at the context lines (the ^ marks the spot).
3. Fix the first error and check again — later errors only show once the first is gone.
4. Optionally show the normalized YAML or the JSON to see how the data is really read.

Formula

valid = the text parses as one or more YAML documents (js-yaml loadAll)

The check covers syntax: indentation, quoting, brackets, anchors and aliases, tags and duplicate keys. It does not check a schema — whether a Kubernetes field name is spelled right, for instance — because that depends on the program that reads the file.

Example

In the sample Deployment, containers holds a list whose single item has the keys name, image and ports. If you indent image: by one extra space, the parser stops with bad indentation of a mapping entry on that line: the key no longer lines up with name: above it. Put it back in the same column and the result returns to Valid YAML — 1 document, 15 keys, 2 list items, nesting depth 8.