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JSON Formatter / Validator / Minifier

Paste or type your JSON. Format it with 2 or 4 spaces, minify it, or just validate. Everything stays in your browser.

How JSON Formatter works

JSON Formatter takes raw JSON text you paste into the editor and returns it indented, coloured, and valid, or tells you exactly where the syntax error is. It also minifies JSON to strip all whitespace for size-sensitive payloads. Every character you type or paste stays in the browser tab; nothing you enter leaves your device.

The formatter parses your JSON with the browser's native JSON.parse, which means it respects the JSON specification precisely and will flag trailing commas, unquoted keys, or control characters that some lenient parsers silently accept. If you want to validate before sending JSON to an API, this is a fast, offline-capable check.

Written by Bastien Sulyan

How to use JSON Formatter, step by step

  1. Paste your JSON text into the input area.
  2. Click 'Format' (or use the keyboard shortcut) to indent and syntax-highlight the output.
  3. Review any error message, which includes the line and column of the first syntax problem.
  4. Click 'Minify' to collapse the formatted JSON back to a single line.
  5. Copy the result from the output area using the copy button.

Common use cases

  • A backend developer receives an API response as a minified blob and needs to read its structure before debugging a parsing issue.
  • A QA engineer validates a JSON configuration file before deploying it to a staging environment.
  • A data analyst wants to inspect a downloaded JSON dataset and check its nesting depth before writing transformation code.
  • A frontend developer needs a minified version of a large JSON fixture to embed in a test file.

Frequently asked questions

Is the JSON I paste sent to any server for processing?

No. The formatting and validation run entirely in your browser using the native JSON.parse function and a local pretty-printer. Nothing you paste here is transmitted. Open your browser DevTools, check the Network tab while formatting, and you will see no outgoing request carrying your text.

What JSON syntax errors does the tool detect?

The tool uses the browser's JSON.parse, which enforces strict RFC 8259 compliance: trailing commas in objects or arrays, single-quoted strings, unquoted property keys, and bare control characters all cause a parse error with a message indicating the approximate position of the problem. It checks structure only: it does not validate your data against a JSON Schema, so a document that parses cleanly can still be wrong for your application.

Can I format very large JSON files?

The tool handles text you paste into the editor, so the practical limit is the amount of text your browser tab can comfortably hold. Files up to a few megabytes format quickly. Very large JSON (tens of megabytes) may be slow and is better handled by a command-line tool such as jq.

Does the formatter preserve key order?

Yes. The formatter does not sort or reorder keys. It re-serializes the parsed object using JSON.stringify, which preserves insertion order in modern JavaScript engines. The only change is whitespace.

Can I use this tool to compare two JSON objects?

The formatter itself shows one JSON at a time. To compare two objects, format each one separately, then paste both into a plain text diff tool. The indented output makes structural differences easy to spot line-by-line.

Does the JSON formatter work offline?

Yes, once the page has loaded. Because the formatting logic is pure JavaScript running in the browser, you can disconnect from the network and continue formatting JSON without interruption.

Can I format JSON on my phone, and is an account required?

Yes to both being fine: no account, no sign-up, and the formatter is a plain text area that works the same on a mobile browser as on a computer, useful for quickly checking an API response while away from your desk.