JSON Uglify
Uglify JSON in your browser. Mangle object keys into short names, compact the payload — files stay on your device.
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Mangles object keys and strips whitespace locally.
Nothing leaves this device. No account required.
Mangle JSON keys locally
JSON Uglify is the JSON analogue of JavaScript mangle.properties: it rewrites object keys to short identifiers, then emits a single line. String values, numbers, booleans, null, and array order stay as they were. The same original key maps to the same short name everywhere in that run. The next click draws a new mapping via Math.random.
Not a drop-in payload
Consumers that look up userId will not find it after uglify. Download the key map (original → mangled) if you need to reverse the names later. The map is not shown in the editor; it is a separate file on purpose. Do not ship uglified JSON to an API that still expects the original shape.
Whitespace-only compression is a different tool: JSON Minifier keeps keys and only strips insignificant space. To inspect or pretty-print the original names, use the JSON Formatter.
What the parser rejects
Input must be strict JSON. Trailing commas, comments, and JSONC fail with a line and column when the engine provides them. Numbers pass through JavaScript’s JSON rules (IEEE 754). Array indices are not keys and are not mangled.
When not to uglify
Do not uglify configs humans still edit, fixtures you diff in git, or public API examples. Do not treat this page as encryption: short names are guessable, and the map undoes the rename. Secrets in the paste stay in this tab, but they are still on this machine.
Proof it does not upload
Open DevTools → Network, paste a payload, uglify it. You should not see the JSON posted to Formatly. Parsing, mangling, and stringify run here.