JSON Formatter & Validator: Format and Validate JSON Free Online

Format and validate JSON instantly

PDFSpot's free JSON Formatter beautifies or minifies JSON in your browser. Nothing is sent to a server — your data stays private.

1. 1Go to the JSON Formatter tool above.
2. 2Paste your JSON into the input box.
3. 3Click Format to get nicely indented, readable JSON.
4. 4Click Minify to compress it into a single line for production use.
5. 5Copy the output directly from the result box.

What is JSON?

JSON (JavaScript Object Notation) is a lightweight text format for storing and exchanging data. It uses key-value pairs and arrays, and is readable by both humans and machines. It is the standard format for REST API responses, configuration files, and data interchange between web services.

A simple example: {"name": "PDFSpot", "tools": 33, "free": true}

JSON must follow strict syntax rules — missing quotes, trailing commas, or mismatched brackets will cause a parse error.

JSON formatting vs minifying

Formatting (also called "beautifying" or "pretty-printing") adds indentation and line breaks to make JSON easy to read. This is what you want when debugging, reviewing an API response, or writing a config file.

Minifying removes all whitespace and line breaks to produce the smallest possible file. This is what you want in production — smaller files mean faster API responses and lower bandwidth costs. A minified JSON file can be 20–40% smaller than its formatted version.

Common JSON syntax errors

These are the most frequent JSON mistakes that cause parse errors:

Trailing commas — JSON does not allow a comma after the last item in an array or object. {"a": 1, "b": 2,} is invalid.

Single quotes — JSON strings must use double quotes. {'name': 'John'} is invalid.

Unquoted keys — Object keys must be quoted strings. {name: "John"} is invalid.

Comments — JSON does not support comments. // this is not allowed inside JSON.

Undefined and NaN — These JavaScript values are not valid JSON. Use null instead.

The JSON Formatter catches all of these and shows you where the error is.

JSON vs JSONC vs JSON5

Standard JSON is strict. Some tools and config files use relaxed variants:

JSONC (JSON with Comments) — allows // and /* */ comments. Used by VS Code settings files (settings.json).

JSON5 — allows trailing commas, single quotes, and comments. Used in some build tool configs.

Our formatter works with standard JSON. If you are working with JSONC or JSON5, strip comments and trailing commas first.

Working with large JSON files

If you are dealing with a very large JSON file (thousands of lines), formatting it in a browser tool is still fast — JSON parsing is handled by the JavaScript engine natively. However, for files over a few MB, consider using a dedicated editor like VS Code with the Prettier extension, which can handle arbitrarily large files without browser memory limits.