JSON Formatter
Format (pretty-print) or minify JSON and validate it — fast and private.
Minified or messy JSON is nearly impossible to read, and a single misplaced comma breaks it. JSON Formatter pretty-prints JSON with clean indentation, minifies it back down, and flags errors — so you can read, tidy and validate JSON in your browser.
How to use json formatter
- 1. Paste your JSON.
- 2. Format (pretty-print) or minify it; invalid JSON is flagged.
- 3. Copy the result.
When to use JSON Formatter
Read an API response
Pretty-print a wall of minified JSON into something you can actually read.
Find a syntax error
Validate JSON to catch the missing comma or bracket that's breaking it.
Minify for transport
Strip whitespace to shrink JSON before embedding or sending it.
The errors you'll see most often
JSON is stricter than JavaScript. The usual culprits: a comma after the last item in a list or object, keys or strings in single quotes instead of double quotes, comments (// or /* */), and unquoted keys. Values such as undefined, NaN or Infinity aren't allowed either. The error message names the problem and the position in the text where parsing stopped — the mistake is at or just before that spot.
Watch out for very large numbers
Formatting parses the JSON into numbers and writes it back out. Integers above 9,007,199,254,740,991 (2^53 − 1) can't be represented exactly in a browser, so a 19-digit ID like 1234567890123456789 can come back with its last digits changed. If your data has IDs that long, they should be sent as strings ("id": "1234567890123456789") — a good habit for any API.
Frequently asked questions
Does it tell me what's wrong with invalid JSON?
Yes — it flags that the JSON is invalid so you can locate and fix the problem.
Can it both format and minify?
Yes — pretty-print for reading, or minify to remove all whitespace.
Is my JSON uploaded?
No — it's parsed entirely in your browser, so sensitive data stays local.
Does formatting change my data?
No — keys, values and their order stay the same; only whitespace changes. The one exception is integers larger than 2^53, which browsers can't store exactly (see above).
How big a JSON file can it handle?
Several megabytes format instantly. Very large files (tens of MB) depend on your device's memory, since everything runs in the browser.