JSON Formatter & Validator

An API response arrives as one enormous line. A config file won't load and the error says “Unexpected token } in JSON at position 1834”. A colleague pastes JSON into Slack with smart quotes. Reading or fixing JSON by eye is miserable.

This formatter pretty-prints JSON with 2- or 4-space indentation, minifies it back to a single line, sorts object keys alphabetically for easier comparison, and validates it. When the JSON is broken it tells you the line and column of the problem, plus a hint for the two most common mistakes: single quotes and trailing commas.

It uses the browser's native JSON.parse, the same strict parser your JavaScript code uses, so “valid here” means valid in production.

Because nothing is sent to a server, it is safe for API responses that contain tokens, customer records or internal configuration — data you should not paste into random formatter websites.

Sorting keys is the underrated feature: two API responses with the same data but different key order look completely different in a diff. Sort both here, then compare them with the Text Compare tool in line mode and only the real differences remain.

How It Works

1. Paste JSON or open a .json file — up to 20 MB from disk, or any amount pasted.
2. Choose an action — format with 2 or 4 spaces, minify, sort keys A→Z, or validate only. The text is parsed with JSON.parse; on failure the error position is converted to a line and column number.
3. Use the result — the output is regenerated with JSON.stringify, so it is guaranteed valid. Copy it or download it as a .json file.

Compatibility & Support

Supported Input → Output Formats

• Input: JSON text (RFC 8259) pasted or loaded from .json/.txt files
• Output: formatted (2/4 spaces), minified or key-sorted JSON; .json download
• Validation: strict — errors reported with line and column

Unsupported Formats

JSON5, JSONC and JavaScript object literals (comments, unquoted keys, single quotes, trailing commas) are not valid JSON and will be reported as errors — which is useful when a system expects strict JSON. Very large numbers beyond JavaScript's safe integer range (2⁵³) lose precision when re-formatted, so be careful with 64-bit IDs.

For converting JSON arrays to spreadsheets use JSON to CSV; for the reverse, CSV to JSON.

File Size Limits

Files up to 20 MB can be opened. Formatting multi-megabyte JSON is fast on desktops; on phones, very large documents may take a few seconds to render in the output box.

Formatting changes size in both directions: 2-space pretty-printing typically adds 15–30% to a minified document, and minifying a hand-written config file removes a similar amount. Neither changes the data, so you can switch back and forth safely.

Who Should Use This Tool?

• Students: A web-development student formats API responses from a class project to understand their structure.
• Freelancers & Designers: A no-code builder validates the JSON body of a Zapier or Make webhook before pasting it into an automation.
• Office Professionals: An analyst formats a JSON export from a SaaS tool to read field names before mapping them into a report.
• Developers: A backend developer finds the trailing comma breaking a package.json by its line and column in seconds.

Why This Tool Beats the Alternatives

• No upload — important for API keys, tokens and personal data.
• Strict validation identical to JavaScript's own parser.
• Helpful hints for the most common JSON mistakes.
• Key sorting for easy diffs, which many formatters skip.
• Fast, ad-light and free.

Pro Tips

• Sort keys in both files, then compare them with the Text Compare tool in line mode to find real differences.
• If JSON copied from a chat app fails, look for curly “smart quotes” — replace them with straight double quotes.
• Minify only for transport; keep formatted JSON in version control so diffs stay readable.

Paste your JSON above and click Format or Validate.