I Hate JSON

JSON formatter — paste, format, done

100% client-side

Input

empty
Or press Ctrl+Enter · max 50MB

Formatted

Your formatted JSON will appear here.

Two-space indent, syntax highlighted, ready to copy.

Format JSON without uploading it anywhere

Paste JSON into the left panel, press Format or Ctrl+Enter, and the formatted result appears on the right with two-space indentation and syntax highlighting. Copy it with one click or download it as a .json file.

Everything runs in your browser. Your JSON is parsed by a Web Worker on your own machine and never sent anywhere — there is no upload, no account, and no server-side processing. You can check: open the network tab and format a file, and you will see no requests.

Built for files that break other formatters

Parsing and formatting a 50MB document with JSON.parse on the main thread locks the browser tab for seconds — the page stops scrolling and looks crashed. This tool does that work in a Web Worker instead, and reads uploaded files inside the worker too, so the large string never touches the UI thread. A 44.8MB file formats in about 2.7 seconds with the page still responsive.

Errors that tell you where the problem is

When JSON does not parse, most tools hand you the browser message verbatim — often "Unexpected token" with no position at all. This one scans the grammar itself to find the first construct that cannot be parsed, then reports the line and column, draws a caret under the offending token, and selects that exact token in your input so you can fix it immediately.

Questions

Is my JSON uploaded to a server?

No. Formatting happens entirely in your browser using a Web Worker. Nothing is transmitted, stored or logged.

What is the maximum file size?

A hard cap of 50MB, enforced in the browser with a clear message rather than a silent hang. Files above 1MB stay out of the editor so typing remains smooth.

What indentation does it use?

Two spaces. The output is exactly what JSON.stringify(value, null, 2) produces, so it matches most linters and editors out of the box.

Does it work offline?

Yes, properly — not just once loaded. After your first visit the whole site is stored on your device, so every tool keeps working with no connection at all, and a repeat visit loads without touching the network. You can add it to your home screen or dock like any other app.