Why is my JSON invalid even though it looks correct?

The most common causes are a trailing comma after the last item in an object or array, single quotes instead of double quotes, or an unquoted object key — all of which are valid in JavaScript but invalid in strict JSON.

Can JSON have comments?

No, the JSON specification has no comment syntax. Some tools support a relaxed variant called JSON5 or JSONC that allows comments, but standard JSON parsers will reject them.

When should I minify instead of beautify?

Minify for production use where the JSON is transmitted over a network or stored in a config file and file size matters; beautify when you're reading or debugging the structure yourself.

JSON Formatter & Validator

Beautify, minify, or validate JSON. View as a collapsible tree. Copy or download your output.

JSON Input

How to use

Paste your JSON into the input box above.
Click Beautify to format with 2-space indentation for easy reading.
Click Minify to compress JSON by removing all whitespace.
Click Validate to check if your JSON is valid — errors show the line number.
Switch to Tree View to explore the JSON structure with collapsible nodes.
Use Copy Output or Download .json to save your result.

About this JSON Formatter

JSON (JavaScript Object Notation) is the standard format for API responses, config files, and data exchange between systems. A single missing comma or quote mark makes an entire JSON document invalid, and unformatted JSON returned by an API is often a single unreadable line. This tool validates the structure and reformats it with consistent indentation.

The most common JSON errors

Trailing commas — {"a": 1, "b": 2,} is invalid; JSON does not allow a comma after the last item, unlike JavaScript object literals
Single quotes — JSON requires double quotes around keys and string values; {'a': 1} is invalid
Unquoted keys — {a: 1} is invalid; every key must be a quoted string: {"a": 1}
Comments — standard JSON has no comment syntax at all; // like this will fail validation
Undefined or NaN values — JSON only supports strings, numbers, booleans, null, objects, and arrays

Beautify vs. minify

Beautified JSON adds line breaks and indentation so nested objects and arrays are readable at a glance — useful for debugging and documentation. Minified JSON strips all unnecessary whitespace into a single line, producing a smaller file size for production APIs and config delivery where every byte transferred matters.

Example

Minified: {"user":"alex","active":true,"roles":["admin","editor"]} becomes, when beautified, a three-line object with the array indented on its own block — far easier to scan when debugging a nested API response.