JSON Formatter

Built for API debugging

Anyone who works with web APIs accumulates JSON that arrives flattened: curl output, webhook deliveries, browser network-tab responses, log lines with embedded payloads. Paste it here and the Format button re-renders nested objects and arrays with consistent indentation so misplaced brackets and unexpected nulls become obvious at a glance. The Minify button does the reverse — stripping every byte of insignificant whitespace — which is what you want before re-sending a request body, storing a fixture, or comparing two payloads by size. Input and output sit side by side, and one click copies the result.

The errors it catches

Validation uses strict JSON parsing, not the more forgiving object-literal syntax JavaScript happens to accept in source code. When parsing fails you get the engine's own error message, including the position where it gave up. The usual suspects:

• Trailing commas after the final element in an array or object — tolerated by some languages, rejected by JSON.
• Single quotes around keys or values — JSON requires double quotes only.
• Unquoted keys written JavaScript-style instead of as strings.
• Smart quotes pasted from documentation sites or word processors, which look identical but are different characters entirely.
• Python-style booleans — True, False, and None must be lowercased to true, false, and null.

Pretty-print versus minify

Use formatted output whenever a human will read it: code review, diffing against yesterday's payload, debugging a malformed response. Use minified output whenever a machine will carry it — over the network, into storage, into a single-line log entry. Both buttons operate on the same parsed value, so switching between them never changes your data. Whitespace inside string values is significant and always preserved untouched; only structural whitespace between tokens is affected.

Sensitive payloads stay put

Debugging often means handling auth responses, session tokens embedded in headers, or customer records pulled from production logs. Pasting that material into a random online validator means uploading it to somebody else's server with unknown retention. Here, parsing and formatting happen entirely inside your browser's memory using its native parser — there is no server round trip at any point, and the page keeps working even once you are offline.