Nothing is uploaded. When you paste text, drop a file or click Sample, the converter reads it locally and runs the whole parse-and-emit pipeline in memory on your device using the bundled js-yaml library, re-converting live (debounced) as you type. There is no server, API, database or tracking in the processing path, so a private Kubernetes secret, an API response or any other sensitive config stays on your machine; the tool works offline once cached, and closing the tab discards everything. The one case where data touches the network is if you paste a remote URL for the tool to fetch, and even then the response is downloaded straight into your browser and converted there, never sent anywhere else — and that fetch needs the remote server to allow cross-origin requests (CORS). The only optional network use anywhere on the site is consent-gated advertising, which never sees your data.

Converting JSON to YAML preserves every value, because YAML 1.2 can represent anything JSON can — the tool proves it by parsing the YAML it produced back into a data structure and deep-comparing it to your input, then showing a green “lossless” badge or an amber “lossy” warning that explains the difference (usually caused by a quoting-style or schema setting). Two things are genuinely outside the data model and cannot survive a JSON round trip: YAML comments (# lines) and the human-readable names of anchors and aliases — a repeated block written with &anchor/*alias is expanded into duplicated data when it becomes JSON. Numeric precision is another edge to watch: very large integers beyond JavaScript’s safe range, or values like 3.10, can normalise, and the lossy badge will tell you when that happens so you can quote the value or switch schema.

The presets pre-load the conventions each toolchain expects. Kubernetes and Docker Compose both want two-space block indentation, no line wrapping and no anchors/aliases (so kubectl, Helm and docker compose read the file cleanly), and Kubernetes adds a leading --- document separator. GitHub Actions and Ansible use similar 2-space block styles, while OpenAPI keeps an 80-column wrap. For the schema, prefer YAML 1.2 (the JSON-compatible core schema) so bare yes, no, on and off remain strings rather than booleans — important because a Kubernetes value like a port name or a country code “NO” must not silently become true/false. You can always start from a preset and then fine-tune indent, quote style or the --- marker in the Advanced panel.

The “Norway problem” is the most famous YAML foot-gun: the YAML 1.1 spec treats a whole family of bare words — yes, no, on, off, y, n and their capitalisations — as booleans, so a list of country codes containing NO turns Norway into false, and on/off flags become true/false unexpectedly. YAML 1.2 fixed this by recognising only true and false, but many real-world parsers still default to 1.1 behaviour. This converter lets you pick the schema: the default YAML 1.2 (JSON-compatible) schema keeps those words as plain strings, and you can additionally set the quote style to force double or single quotes so any string that looks like a boolean, number or date is quoted in the output. When in doubt, quote it — and the round-trip check will confirm the value came back as the string you intended.