JSON Formatter — How to Read, Format, and Validate JSON Data

Raw JSON from an API response looks like a wall of text. Learn how to format, validate, and work with JSON data effectively.

You just hit an API endpoint and got back a response. It's JSON, technically, but it looks like this:

{"users":[{"id":1,"name":"Sarah","email":"sarah@example.com","roles":["admin","editor"],"settings":{"theme":"dark","notifications":true}}]}

Good luck reading that. This is where a JSON formatter becomes your best friend.

Formatting vs validating

Formatting (also called "prettifying" or "beautifying") takes compressed JSON and adds whitespace — indentation, line breaks — to make it human-readable. The data doesn't change; it just becomes easier to read.

Validating checks whether the JSON syntax is correct. Missing comma? Unclosed bracket? Trailing comma (not allowed in JSON, unlike JavaScript)? A validator catches these errors and tells you exactly where they are.

Common JSON mistakes

Trailing commas. {"a": 1, "b": 2,} — That last comma is invalid JSON, even though JavaScript allows it.

Single quotes. {'key': 'value'} — JSON requires double quotes. Always.

Unquoted keys. {key: "value"} — Valid JavaScript, invalid JSON. Keys must be strings in double quotes.

Comments. JSON doesn't support comments. Period. If you need comments, consider JSONC or YAML.

Format and validate

Toolozo's JSON Formatter formats, validates, and minifies JSON data. Paste in messy JSON, and see it properly indented with syntax highlighting. Errors are highlighted so you can fix them instantly. Everything runs in your browser — your API responses, config files, and data stay private.

Need to convert between formats? Check out JSON to YAML, JSON to XML, or JSON to TypeScript converters.