How to format, validate and fix JSON

JSON is the lingua franca of APIs and configuration files. It's also strict: a single misplaced comma makes the whole document invalid.

Make it readable

Paste minified JSON into the JSON formatter to get indented, multi-line output. Turning on Sort keys orders object keys alphabetically at every level, which makes two versions of a document easy to compare with Text compare.

Find the error

The JSON validator reports the exact line and column of the first error and shows a caret under it. The usual suspects:

Mistake	Invalid	Valid
Trailing comma	{"a": 1,}	{"a": 1}
Single quotes	{'a': 1}	{"a": 1}
Unquoted key	{a: 1}	{"a": 1}
Comment	{"a": 1 // note}	not allowed
Special numbers	NaN, Infinity	use null or a string

JavaScript object literals accept all of the invalid forms, which is why copying an object from code into a .json file often fails.

Minify for production

JSON minifier removes all whitespace outside strings. It typically saves 10–30% on indented files; gzip or Brotli compression on your server will save far more on top.

Convert to and from spreadsheets

Need to hand data to a non-developer? JSON to CSV flattens nested objects into columns like address.city, and CSV to JSON goes the other way, turning numbers and booleans into proper JSON types.

Is it safe to paste API responses?

These tools run entirely in your browser, so production data isn't transmitted. As a habit, still redact tokens and personal data before sharing JSON with anyone.