Free YAML Formatter & Validator

The YAML Formatter is a free online tool that formats, beautifies, and validates YAML documents to ensure proper structure and syntax.

Yes, it is completely free with no registration required. All formatting happens client-side in your browser.

Yes, the YAML Formatter checks your YAML for syntax errors and provides clear error messages to help you fix any issues.

Absolutely. The YAML Formatter & Validator processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the YAML Formatter & Validator is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the YAML Formatter & Validator in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The YAML Formatter & Validator works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

This error almost always means the parser hit indentation it didn't expect, not a literally missing colon. Because YAML is whitespace-sensitive, a tab where spaces belong, a key indented one space too far, or a value placed on the wrong nesting level makes the parser lose track of the current map and report a confusing message at a line that looks fine. Other common triggers are an unquoted value containing a colon (like a time "12:30" or a URL), or a list item that isn't aligned with its siblings. This tool parses your document with the js-yaml library, so it catches the same problems a real parser would, then shows a clear error pointing you toward the structural mistake. Paste your YAML above to find exactly where the indentation or colon breaks.

Two spaces is the most common YAML convention and the default for Kubernetes manifests, GitHub Actions workflows, and most CI configs, while 4 spaces is sometimes used for readability in deeply nested files. The one rule that matters is consistency: YAML treats indentation as structure, so mixing widths within a document breaks parsing. Strictly speaking, the YAML spec forbids tab characters for indentation, which is why a stray tab is such a frequent cause of errors. This formatter lets you pick 2 spaces, 4 spaces, or tabs, then re-indents every level uniformly so nested maps and sequences line up predictably. That makes the output match a house style or linter config and keeps diffs clean. Paste your file and choose your indent size to normalize the whole document at once.

YAML and JSON describe the same underlying data model — maps, lists, strings, numbers, booleans, and null — so any valid JSON can be expressed as YAML and vice versa. The differences are about syntax and ergonomics: JSON uses braces, brackets, and quotes and is strict and compact, making it ideal for APIs and machine exchange; YAML uses indentation instead of braces, allows comments, and is far easier for humans to read and edit, which is why config files favor it. This tool converts in both directions: paste YAML and switch to the JSON tab for valid pretty-printed JSON, or paste JSON to get readable YAML. It is useful for moving a config between tools or sanity-checking what a YAML file actually deserializes to. Paste your document above and switch tabs to convert instantly.

Older YAML 1.1 parsers interpret a long list of "truthy" words as booleans, including yes/no, on/off, and y/n, alongside true/false. So a value like country: NO (meaning Norway) or a port labeled on can silently become a boolean and break your config in confusing ways. The same applies to unquoted version numbers like 1.10, which can be read as a float and lose the trailing zero. The safe fix is to quote any value you want treated as a literal string: "no", "on", "1.10". This tool's built-in linting flags these ambiguous truthy values so you catch them before they reach a pipeline, and its quote-style option can force quotes on strings. Paste your YAML above to surface ambiguous booleans and reformat with consistent quoting.

Anchors and aliases let you reuse a chunk of YAML without repeating it. You mark a node with an anchor using &name, then reference it elsewhere with an alias *name, and many configs also merge anchored maps with the << key. This keeps files DRY — handy for shared environment blocks or repeated service definitions — but it can make a document harder to read in isolation, and some tools that consume your YAML don't resolve aliases the way you expect. Expanding aliases resolves every *reference back to the actual value from its &anchor, producing self-contained output where nothing depends on a definition elsewhere in the file. That is useful when you need a flattened config to hand off, debug, or feed into a stricter parser. Paste your YAML above and enable expand aliases to inline every reference automatically.