Why convert JSON to YAML locally
Helm values, GitHub Actions, Docker Compose, and Ansible inventories are YAML. The source of truth on many APIs, Postman collections, and generated configs is JSON. Pasting that JSON into a random website formatter is a bad habit when the payload includes tokens, connection strings, or customer records. This page runs JSON.parse and a YAML serializer in your tab. There is no POST body, no pastebin, and no log of what you typed.
The converter updates on every input change. Empty textarea: empty state, export buttons disabled. Valid JSON: YAML appears immediately with the indent you picked (2 Spaces by default, or 4 Spaces). Invalid JSON: a warning banner with line and character, red focus ring on the input, Copy YAML and Download .yaml File disabled. That is the whole contract. You should be able to paste, fix one comma, and copy without fighting a submit button.
JSON.parse(source)dumpYaml(value, indentSpaces)error: line L, character C
Auto-fix is on by default because humans paste from Slack, Word, and JavaScript object literals. Smart quotes become straight quotes. Simple single-quoted strings become JSON strings. Trailing commas before } or ] are stripped, and strings are skipped so a comma inside "a, b" is left alone. If you are auditing a payload that must fail on any deviation from RFC 8259, turn the toggle off and read the banner.
YAML output rules on this page
Objects dump as key: value lines. Nested objects and non-empty arrays go on the next indent level. Empty objects print as {} and empty arrays as []. JSON null, booleans, and finite numbers stay unquoted. Strings that look like YAML booleans (yes, on, null) or that contain :, #, or whitespace are JSON-quoted so a later YAML parser does not recast them. Keys that are not plain identifiers are quoted the same way.
Array items use a leading hyphen. If an item is an object, the first field sits on the hyphen line and the rest of the fields line up under it. That matches what Kubernetes and Compose files look like, which is the usual reason people convert at all. Indent is only spaces: 2 or 4. Tabs are not used. Download writes converted.yaml with UTF-8 text. Copy uses the Clipboard API, with a 1px off-screen textarea fallback if the permission is blocked.
Depth is capped at 50 levels. A generated JSON blob with runaway nesting will throw a clear error instead of walking until the call stack dies. Circular references are rejected the same way. You will not get a useful YAML file from a cycle, and you should not freeze the browser trying. For huge files, paste a slice: this is a review tool, not a 50 MB pipeline.
How this sits next to other Veomark developer tools
Use this converter when the destination is YAML. Keep a JSON formatter (queued on the hub as JSON Formatter and Validator) for pretty-print and schema work that must stay JSON. If you are shipping CSS rather than config, use the CSS Minifier and Optimizer on the same site. Campaign links belong on the UTM Builder, not in this textarea.
YAML 1.1 has type-guessing surprises that JSON does not. This dump quotes the dangerous strings on purpose. It does not emit document start markers or comments. If you need a full round-trip YAML 1.2 processor with anchors, use a local CLI. This page is for the common path: take JSON from an API, get readable YAML, paste it into a values file, and do not leak the payload to a hosted formatter.
Clear wipes the textarea and returns the empty state. Download writes UTF-8 converted.yaml. If parse fails after auto-fix, read the banner, fix the reported line, and type again. The YAML pane does not keep a stale successful dump next to a new syntax error.
Frequently Asked Questions (FAQ)
Does this JSON to YAML converter upload my data?
No. Parsing, auto-fix, and YAML serialization run in your browser with client-side JavaScript. The payload never leaves the page. That is the point for API bodies, Kubernetes snippets, and secrets that should not hit a third-party formatter.
What does auto-fix minor formatting do?
When the toggle is on (the default), the tool rewrites smart quotes to straight quotes, converts simple single-quoted strings to JSON double quotes, and strips trailing commas before } or ]. Turn it off if you want a strict JSON.parse and a line/character error for every defect.
How are syntax errors reported?
Invalid JSON lights a live warning banner with the line and character when the engine reports a position. Copy YAML and Download .yaml stay disabled until parse succeeds. Empty input is not an error: the YAML pane shows a clean empty state.
What happens with deep or circular structures?
The walker stops at 50 nested levels and reports the limit instead of hanging the tab. Circular references are caught the same way. JSON.parse of text cannot create cycles by itself, but the guard is still there so a bad object graph cannot freeze the page.