Private JSON Formatter & Validator

100% client-side. Format JSON without rounding large numbers or reordering keys. Your text is never uploaded or stored.

Input

Output

Indent

Why a client-side JSON tool?

Many online formatters send your text to a server. JSON often contains API keys, tokens or customer data. This tool tokenizes and formats the text in your browser without parsing whole numbers into floating-point values or uploading content. You can verify this in your browser's network tab: formatting makes no requests.

Common JSON errors

Trailing commas after the last item are not allowed; the repair button can remove them.
Keys and strings need double quotes; the repair button can convert simple single-quoted strings.
Comments (// or /* */) are not part of JSON.
undefined, NaN and Infinity are not valid JSON values.

Large numbers and duplicate keys

Formatting preserves number tokens exactly, including integers larger than 2⁵³, exponent notation and trailing decimal zeros. Duplicate object keys are preserved and reported because software may interpret them differently. Sorting keys changes their order; avoid it when order is significant to your workflow.