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Quick answer
A JSON formatter pretty-prints minified or messy JSON by adding consistent indentation and line breaks so it's readable. JSON Dev Tools formats your JSON entirely in your browser using JSON.parse() and JSON.stringify() — your data is never uploaded to a server. Paste JSON, click Format, and read or copy the result.
Key takeaways
- Formatting only changes whitespace — the data itself is untouched.
- It validates as it formats — invalid JSON is flagged with the error position.
- Choose your indentation — 2 spaces, 4 spaces, or tabs.
- 100% private — runs client-side; nothing you paste leaves your browser.
How the JSON Formatter Works
- Your input is parsed with
JSON.parse()— if the JSON is invalid, the error position is highlighted so you can fix it before formatting. - The parsed result is re-serialised with configurable indentation (2 spaces, 4 spaces, or tabs) using
JSON.stringify(parsed, null, indent). - The Repair button auto-fixes the most common issues — trailing commas, single-quoted strings, unquoted keys — before re-formatting.
- Everything runs in your browser; your JSON is never sent to a server — see is it safe to paste JSON into an online formatter?
When to Use the JSON Formatter
- When an API returns a single-line JSON response and you need to inspect specific fields.
- Before committing a JSON config file to source control — formatted JSON produces readable diffs in pull requests.
- When debugging a
JSON.parse()error and you need to see the structure clearly to find the problem. - After copying a minified JSON payload from browser DevTools and wanting to read it without squinting.
Frequently Asked Questions
What does formatting JSON do?
JSON formatting adds indentation and line breaks so nested objects and arrays become easy to read. The data itself does not change — only the whitespace presentation does.
Can I use this tool for API responses?
Yes. Paste any API JSON response and click Format to inspect its structure, keys, and values. The tree view below the editor lets you expand and collapse nested objects interactively.
Is my JSON sent to a server?
No. All formatting, validation, and tree rendering happens entirely in your browser using JavaScript. Your data never leaves your device.
What is the difference between JSON Formatter and JSON Validator?
A formatter adds indentation to make JSON readable — it requires valid JSON first. A validator checks whether JSON is syntactically correct and reports errors. This tool does both: it validates as part of the format step and surfaces any errors before formatting.
Can I choose 4-space indentation?
Yes. Use the indentation selector in the toolbar to switch between 2-space, 4-space, and tab indentation before clicking Format.