YAML Validator checks your YAML document for syntax errors before it breaks a deployment. YAML's whitespace-sensitive structure makes subtle bugs easy to introduce — a single stray tab character, wrong indentation depth, or missing space after a colon turns a valid-looking config into a parse error that crashes Kubernetes pods, fails GitHub Actions workflows, or blocks Docker Compose services. Paste your YAML and get an exact error message with line and column numbers, without touching a terminal.
YAML uses indentation depth to define nesting — a 2-space shift means "child of the above key", and any misalignment breaks the entire document structure. YAML also forbids tab characters: only spaces are valid for indentation. The validator parses the document using a strict YAML parser and reports the first syntax error with its exact position, so you can fix it without scanning the whole file manually.
YAML's specification explicitly bans tab characters for indentation to avoid ambiguity — different editors render tabs as 2, 4, or 8 spaces. Using only spaces makes indentation deterministic regardless of editor settings. This is the most common reason a YAML file that looks correct in one editor fails in another.
This usually means a colon appears in an unquoted string value, or a key-value pair is missing a space after the colon. For example, url: https://example.com/path fails because the colon in the URL is treated as a YAML separator. Fix it by quoting the value: url: "https://example.com/path".
A syntax error means the document cannot be parsed at all — wrong indentation, missing colons, invalid characters. A schema error means the document is valid YAML but doesn't match the expected structure for the application (for example, a Kubernetes Deployment missing the apiVersion field). This tool catches syntax errors; schema validation requires knowing the specific schema.
Yes. Lines starting with # are comments and are ignored by the parser. Inline comments work too, but must have a space before the #: "key: value # comment" works, but "key: value#comment" fails because the # is treated as part of the value.
No. Validation runs entirely in your browser using a JavaScript YAML parser. Your configuration files — including any secrets, API keys, or credentials they contain — never leave your device.
YAML supports multiple documents in one file separated by ---. The validator checks the structure of each document. If one document has a syntax error, it will be reported with the line number pointing inside that document block.
Tool workspace
Free YAML validator online — instantly catch indentation errors, tab characters, and syntax mistakes in Kubernetes, Docker Compose, and GitHub Actions configs. No login.
Output
Input
name: John
Output
