JSON Formatter

The usual culprits are a trailing comma after the last item, single quotes instead of double, unquoted keys, or a comment. JSON permits none of these even though JavaScript does. Check the very end of arrays and objects first.

A parser reports where it could no longer continue, not where you made the mistake. Forget a closing brace on line 12 and the error may surface on line 340 when the parser runs out of input. Format the document and look for a block that does not close where you expect.

Yes. Parsing happens entirely in your browser and nothing is sent anywhere. This matters because API responses routinely contain access tokens, session identifiers and customer records — pasting one into a server-side formatter means handing that data to a third party.

No. It validates syntax — whether the document parses. Checking that it has the right fields with the right types is schema validation, which requires JSON Schema and a separate validator.

For data transmitted over a network at volume, where removing whitespace measurably reduces bandwidth. For anything a human will read or debug, minifying is counterproductive.

1) Open the tool. 2) Enter or upload your input. 3) Get your result instantly. Everything happens locally — nothing is uploaded.

Use it whenever you need to beautify an API response, validate a config file, fix a broken JSON payload, or browse a deeply nested object — without uploading the data anywhere.

Yes. JSON Formatter runs 100% in your browser. Inputs are never uploaded, stored, or logged — safe for confidential content.

JSON Formatter performs lossless operations — your content is not re-encoded or downgraded.

JSON Formatter supports JSON, YAML, XML, CSV, TOML and other developer-friendly text formats

Yes — JSON Formatter is completely free, with no registration, no watermarks, and no usage limits.

No. Parsing, formatting, validation, and the tree view all run in your browser via native `JSON.parse`. Open DevTools → Network after the page loads and you will see zero outbound requests when you click Format. This is the reason engineers paste production API responses with auth headers, customer IDs, and internal IPs here instead of jsonformatter.org.

Up to about 5 MB via the upload button, and effectively unlimited via paste — bound only by your browser tab memory. A 2 MB payload with 50,000 nodes formats in well under a second on a modern laptop. For multi-hundred-MB log dumps, stream them with `jq` instead; the browser is not the right tool at that scale.

Strict JSON disallows trailing commas, single-quoted strings, unquoted keys, comments, and `undefined`. The error line and column shown beneath the editor points to the exact character — usually a trailing comma after the last array item or an unescaped quote inside a string. Fix that one spot and the rest validates.

Not directly — those allow comments, trailing commas, and unquoted keys that strict JSON rejects. Strip the comments first, replace single quotes with double quotes, and quote the keys. For TypeScript object literals, use the [LINK:TypeScript to JavaScript|/tool/typescript-to-javascript] tool first, then paste the result here.

Yes — the tree renders lazily on expand, so a 50,000-item array opens instantly with a collapsed root node and only renders children when you click to expand. For very wide arrays (>10,000 items at one level) the formatted text view is faster to skim than the tree.