DEVELOPER TOOLS · 2026

JSON Formatting 101: Why You Should Validate Your JSON

JSON (JavaScript Object Notation) is the standard format for exchanging data between apps, APIs, and config files. A single misplaced comma can break an entire request — here's what to watch for:

1. Trailing commas aren't allowed — unlike JavaScript object literals, standard JSON will fail to parse if there's a comma after the last item in an array or object.
2. Keys and strings need double quotes — single quotes are a common copy-paste mistake that breaks JSON parsers.
3. No comments allowed — JSON has no syntax for comments (// or /* */), unlike JavaScript or JSON5.
4. Numbers can't have leading zeros — and there's no support for NaN, Infinity, or undefined.
5. Always validate before you ship — a broken JSON config or API payload can silently fail in production; catching it early with a formatter/validator saves real debugging time.

Paste your JSON into our free JSON Formatter & Validator to instantly beautify, minify, or catch syntax errors — entirely offline, nothing is ever uploaded.

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