JSON Formatter

How it works

This JSON formatter uses your browser's built-in JSON.parse and JSON.stringify to process JSON entirely on your device. Paste raw JSON, then format it with your preferred indentation (2 spaces, 4 spaces, or tabs), minify it to a single line, or validate it with error details including the position of any syntax issues.

Your data never leaves your browser. No server, no signup, no tracking. It works on any modern browser, on both mobile and desktop.

Frequently asked questions

Why does it warn about large integers?

JavaScript parses every JSON number as a 64-bit float, so whole numbers larger than 2^53 (like 64-bit database IDs) silently lose their last digits. This tool scans the raw text and warns you when an integer exceeds that safe range, since the reformatted output would otherwise be wrong without any error.

What happens to duplicate keys in an object?

The JSON spec allows duplicate keys but does not define which wins, and browsers keep only the last one. When the input has a repeated key in the same object, the formatter warns you and lists the offending keys so you notice the data loss before copying the output.

Does formatting change my numbers, key order, or Unicode?

Key order and Unicode characters are preserved exactly. Numbers are re-serialized, so redundant forms are normalized: 1.0 becomes 1, 1e3 becomes 1000, and trailing zeros are dropped. The values are equal, but the text is not byte-for-byte identical.

Does it accept comments or trailing commas?

No. This validates strict JSON per the spec, so JSON5, JSONC comments, single quotes, and trailing commas are reported as syntax errors with the line and column of the problem. Remove them before formatting.

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