YAML Validator
Check whether pasted YAML is syntactically valid. Invalid input is reported error-by-error with the exact line, column and reason; valid input gets a structural summary — document count, top-level type (mapping/sequence/scalar) and key/item counts. Runs entirely in your browser.
Input
Output
| Line | Column | Message |
|---|---|---|
| No data yet | ||
Guides
Paste any YAML and instantly find out whether it is syntactically valid. If it isn't, the YAML Validator points to the exact line and column of every mistake and explains what went wrong — bad indentation, a stray tab, an unclosed flow collection, a duplicate key, and so on. If it is valid, you get a quick structural summary instead of a bare "OK": how many documents the file contains and, for each one, the top-level type and how many keys or items it holds.
Everything runs entirely in your browser. Your YAML is never uploaded to a server, which makes the tool safe for config files, secrets, CI pipelines and Kubernetes manifests.
How to use it
- Paste or type your YAML into the input box (or click Try an example to load a sample).
- The result updates as you type. The Result panel shows a one-glance verdict.
- When something is wrong, the Errors table lists each problem with its line, column and message. Copy the report or download it as a CSV.
What "valid" means here
The validator checks that the text is well-formed YAML — that a parser can read it without error. For a valid file it reports:
- The number of
----separated documents in the stream. - The top-level type of each document: a mapping (key/value object), a sequence (list), or a scalar (a single value).
- The key count for mappings and the item count for sequences.
It does not check your data against a schema — it won't tell you that port should be a number or that a required field is missing. It answers one question well: is this valid YAML syntax?
Why does it report line and column so precisely?
The tool parses your text with a real YAML parser that records the exact position of every error, rather than stopping at the first one. That means a document with several mistakes shows all of them at once, each pinpointed — so you can fix a whole file in one pass instead of running the check over and over.
It says my valid-looking YAML is invalid — why?
The usual culprits are indentation (YAML forbids tabs for indentation — use spaces), mixing indentation levels within the same block, using a reserved character (:, #, -) unquoted in a value, or a colon without a following space. The error message and column marker tell you precisely where the parser gave up.
Does it support multiple documents?
Yes. A single file can hold several documents separated by ---, exactly as Kubernetes manifests and CI configs often do. Each document is validated and summarised independently.