Wonderstacked

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JSON Formatter & Validator

The JSON Formatter & Validator is a free online tool that pretty-prints, minifies and validates JSON, reporting the exact line and character of any syntax error. It parses in your browser with the native JSON engine, so payloads containing tokens or customer data are never uploaded.

Last updated · Free, no signup

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What does a JSON formatter and validator do?

A JSON formatter turns compact JSON into an indented structure, minifies formatted data for transport, and checks whether the input follows JSON syntax. This page reports the first parser failure so a missing comma, invalid quote, trailing comma, or unexpected token can be located before the payload reaches an API or application.

Formatting and validation use the browser's native JSON.parse and JSON.stringify implementations with two-space indentation, following RFC 8259 and ECMA-404 behavior. It checks syntax rather than a business schema, and duplicate object keys may still parse with the last value silently replacing earlier ones.