JSONSmith - free, no upload, runs in your browser
JSONSmith formats messy JSON, minifies it for transport, converts between JSON and YAML, and diffs two payloads line by line. It is built for debugging real work - API responses, webhook bodies, config files - and runs entirely in your browser so payloads with tokens stay private.
Real debugging payloads are full of things you should not ship to a random website: bearer tokens, customer IDs, internal URLs. Yet the reflex when a payload looks broken is to paste it into the first formatter that Google shows.
JSONSmith is that formatter without the upload. Parsing, formatting, and diffing happen in your browser, so the reflex becomes harmless.
"What changed between the last working request and this one?" is the most common debugging question for integrations. Paste the old payload on the left, the new one on the right, and JSONSmith highlights the differing lines - no eyeballing two editor panes side by side.
Both inputs can be JSON or YAML; formatting is applied consistently before comparison.
Payloads up to 2 MB. Larger responses should be trimmed to the relevant subtree first.
Yes. Invalid JSON produces a clear error rather than silent failure, so a trailing comma or missing brace is caught immediately.
Yes - YAML can be pretty-printed and JSON can be formatted, and the diff accepts either format on both sides.
No. Formatting, minifying, and diffing are pure browser-side operations. This matters exactly because debug payloads often contain secrets.
Not yet - the current scope is format, minify, convert, and diff.