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JSON Formatter

Format valid JSON, detect errors, and copy clean output instantly.

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Input

Or try an example

Output

Ready to format.Paste JSON to pretty-print and validate it.
Syntax-highlighted output will appear here
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What this tool does

Paste any JSON — minified API responses, broken config files, or deeply nested objects — and get pretty-printed, syntax-highlighted output instantly. If the JSON is invalid, the tool shows a clear error message with the approximate line number. No setup, no configuration, just paste and read.

How to use

  1. 1Paste your JSON into the input area
  2. 2Valid JSON is formatted and highlighted automatically — invalid JSON shows a clear error
  3. 3Copy the formatted result in one click

Common use cases

Format minified API responses

Paste a single-line JSON response from an API and get readable, indented output with syntax highlighting.

Debug broken JSON

Paste invalid JSON and get a clear error message with the approximate line number where the syntax breaks.

Inspect nested data structures

Expand deeply nested objects and arrays into a clearly indented tree so you can trace every key and value.

Prepare JSON for documentation

Format JSON examples before pasting them into docs, READMEs, or Notion pages.

Clean up config files

Reformat minified package.json, tsconfig, or any JSON config into a readable structure.

Need to clean more than just JSON? The 1-Click Cleaner handles URLs, text, lists, and email/link extraction too.

Why use Doneio

  • No signup required — just open and paste
  • Runs entirely in your browser — nothing is sent to a server
  • Syntax-highlighted output with color-coded keys, strings, and values
  • Clear error messages for invalid JSON with line numbers
  • Available to use without any signup

Frequently asked questions

What is JSON formatting?

JSON formatting (or pretty-printing) adds indentation and line breaks to compressed JSON so it becomes human-readable.

How do I fix invalid JSON?

Paste your JSON here — the tool will show exactly where the syntax error is. Common issues include trailing commas, missing quotes, and unescaped characters.

Does this tool store my data?

No. Everything runs in your browser. Nothing is sent to a server or saved to a database.

Can I format large JSON files?

Yes. The tool handles large payloads directly in your browser. For extremely large files, performance depends on your device.

Is this free to use?

Yes. You can use it right away with no signup required.