YAML Validator
YAML Validator - a browser-based developer tools utility.
Browser tool
About YAML Validator
YAML fails in ways that are hard to see: a tab where spaces were expected, a key indented one space too far, a colon inside an unquoted string. The parser knows exactly where it gave up, and this shows you that position rather than reporting that the file is invalid. Free, online, and usable the moment you arrive. Your YAML is parsed locally, so a file full of credentials is never uploaded, and no account is involved.
How to use it
- Paste the YAML or open the fileA whole config or the fragment you suspect.
- Read the position, not just the messageThe line and column are where parsing failed, which is often one or two lines below where the mistake actually is — an under-indented key is only detectable once the next key arrives.
Why indentation is the usual culprit
YAML expresses structure through indentation, so whitespace is not cosmetic: it is the syntax. Tabs are forbidden outright, and a key indented to the wrong depth is frequently still valid YAML — it just means something different from what you intended, which is worse than an error because nothing complains until the application behaves oddly.
Values that are not the type you expect
Unquoted yes, no, on and off have historically been read as booleans, and a version number like 1.10 is a float that loses its trailing zero. Quoting a value is how you insist it is a string.
What it does not do
- Valid YAML is not correct configuration. This confirms the file parses; whether the keys are the ones your application expects is a question only that application can answer.
- Where a document uses tags or anchors heavily, a parse error can be reported at the point of use rather than at the definition.
Questions people ask
- Why does my file fail on a line that looks fine?
- Because the error surfaces where the parser could no longer continue, which is usually just after the real mistake. Check the indentation of the lines immediately above the reported position.
- Can I use tabs in YAML?
- No. The specification forbids tab characters for indentation, and an editor silently inserting one is a common cause of a file that looks correct and will not parse.
Questions about ToolsVerse itself — privacy, cost, what happens to your files — are answered in the frequently asked questions.
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