JSON Formatter & Validator

JSON (JavaScript Object Notation) is the most widely used data interchange format for web APIs, configuration files, databases, and data pipelines. This free online JSON formatter validates syntax, highlights errors with precise line numbers, and lets you beautify minified JSON with customizable indentation.

When to Use a JSON Formatter

Debugging API responses — paste raw output from curl, Postman, or browser DevTools to see the data structure clearly. Editing config files — format package.json, tsconfig.json, .eslintrc for readability. Validating webhooks — check that incoming JSON from Stripe, GitHub, or Slack is well-formed. Working with databases — format MongoDB documents, Elasticsearch queries, or DynamoDB items.

Common JSON Syntax Errors

The most frequent JSON errors: trailing commas after the last item (valid in JS, invalid in JSON), single quotes instead of double quotes, unquoted keys (all keys must be double-quoted strings), comments (JSON doesn't support // or /* */), and undefined/NaN values (use null instead). This formatter identifies these errors instantly with clear messages.

JSON Format vs Minify

Formatted JSON uses indentation and line breaks for readability — essential during development. Minified JSON removes all whitespace to reduce size — important for API responses and network transfer. This tool supports both: paste minified JSON to beautify it, or click "Minify" to compress. A typical API response shrinks 30–50% when minified.

All processing runs locally in your browser using JavaScript's native JSON.parse() and JSON.stringify(). No data is ever sent to a server.