YAML validator online

Your YAML can be valid and still not mean what you think. Paste the file: you get every syntax error at once, and on top of that the values another parser will read differently.

Use this tool

JSON EDITOR

Validate and normalize YAML with precise diagnostics.

Local validation · safe formatting · your code is never sent

The problem is not syntax, it is the two specifications

YAML 1.1 and YAML 1.2 coexist and they do not read the same. Your editor and modern JavaScript libraries use 1.2; PyYAML and go-yaml use 1.1, and those sit underneath Docker Compose, Ansible and much of the Kubernetes tooling. Same file, two different values, zero errors on both sides.

The Norway problem and its siblings

A list of country codes `[NO, SE, DK]` becomes `[false, "SE", "DK"]` in any 1.1 parser: `no` is a boolean there and a string here. The same happens with `version: 1.10`, which loses the zero and lands on 1.1; with `0700`, which is 700 or 448 depending on who reads it; and with `22:22`, which 1.1 reads as base 60. None of them raises an error.

Every error, not just the first

Most validators stop at the first failure, so you fix it, revalidate, and the next one appears. Here the report arrives complete, with the line, the column and what to write instead, so you make a single pass before you commit.

FREQUENTLY ASKED QUESTIONS

Is my file uploaded?

No. The YAML is parsed with JavaScript inside your own browser and never travels over the network.

What does it find that other validators do not?

The values that are valid but change meaning depending on the parser: `no` and `off` read as booleans in YAML 1.1, versions like `1.10` that lose the trailing zero, integers with a leading zero read as octal, and times like `22:22` converted to base 60. None of those produce a syntax error.

Does it accept multiple documents in one file?

Yes. Documents separated by `---` are all analysed and the findings come back ordered by line, so there is no need to split the file.

Why does my file fail when it looks correctly aligned?

Almost always it is tabs or non-breaking spaces mixed with normal ones. The specification forbids tabs for indentation and a non-breaking space is not a valid space; on screen all three look identical, so the tool flags them separately.

Can I convert it to JSON?

Yes, with the YAML to JSON tool, which uses the same local engine.