DevToolsLab

JSON Formatter

Format · Minify · Validate

Format, minify and validate JSON locally. Errors are highlighted with line and column.

109 chars
InputValid
Output

Your JSON is processed entirely in your browser — nothing is uploaded.

What is a JSON Formatter?

A JSON formatter takes raw JSON text and reformats it with consistent indentation and line breaks so it becomes easy to read. A good formatter also validates the syntax — pointing out exactly where a missing comma, unbalanced bracket, or invalid escape sequence is — and can minify JSON back to a compact one-line form for production use. DevTools Lab's JSON Formatter does all of this directly in your browser, so the data you paste never leaves your device.

Features

  • Pretty-print with 2 / 4 / tab indentation
  • One-click minify (remove all whitespace)
  • Strict validation with line and column error reporting
  • Live character and byte counter
  • Copy / Download / Apply-to-input shortcuts
  • 100% client-side — works offline once loaded

How to use

  1. Paste or type your JSON into the input panel on the left.
  2. Choose an indentation (2 spaces is the most common) or click Minify.
  3. If the JSON is invalid, the exact line and column of the error appears at the bottom.
  4. Use Copy or Download to export the result.

Frequently Asked Questions

Is my JSON data sent to any server?

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No. All formatting, minifying and validation happens 100% inside your browser using JavaScript. The data you paste never leaves your computer.

Does it support JSON5 or comments?

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Currently we follow strict RFC 8259 JSON. JSON5 / JSONC support (trailing commas, comments, single quotes) is on the roadmap.

Is there a size limit?

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There is no hard limit, but very large files (>10 MB) may slow down rendering depending on your device. Formatting itself is fast.

Can I use this offline?

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Yes. After the page is loaded once, the JSON formatter continues to work even without an internet connection.

Why do I get "Unexpected token" errors?

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JSON is strict: keys and strings must use double quotes, no trailing commas, and no comments. The error message shows the exact line and column to fix.

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Canonical: https://devformatlab.com/en/json-formatter