JSON Formatter and Validator

How to use the JSON formatter

• Paste your JSON into the box above, or type it.
• Choose the indentation: 1 to 4 spaces for readable output, or Compact to put everything on a single line.
• Press Format JSON. If the input is valid, the formatted result appears below and can be copied with one click. If it is not, you get the parser's error message, which names the problem and usually its position.

Formatting changes the whitespace, not the structure. Because the text is parsed by your browser's JSON engine, three details can differ from your input, and it is worth knowing them before you copy the result back:

• Keys that look like whole numbers, such as "2" and "10", move to the start of their object in ascending order. Other keys keep their order.
• Integers larger than 9,007,199,254,740,991 (2⁵³ − 1) lose precision: 12345678901234567890 becomes 12345678901234567000. Store long IDs as strings to keep them exact.
• Numbers are written in their shortest form: 1.10 becomes 1.1 and 1e3 becomes 1000.

What makes JSON valid

JSON (JavaScript Object Notation) is a text format for structured data, defined by RFC 8259 and ECMA-404. It looks like JavaScript, but it is much stricter, and most validation errors come from habits that JavaScript allows and JSON does not:

• Keys must be in double quotes. {"name": "Ana"} is valid; {name: "Ana"} is not.
• Strings use double quotes only. 'Ana' with single quotes is rejected.
• No trailing commas. [1, 2, 3,] fails because of the comma before the closing bracket.
• No comments. Neither // ... nor /* ... */ is part of JSON.
• Only JSON values. Allowed values are strings, numbers, objects, arrays, true, false and null. undefined, NaN and Infinity are not.
• Control characters must be escaped inside strings: a line break is written as \n and a tab as \t.

Readable or compact?

Indented JSON is easier to read, review and compare in version control, so it suits configuration files, documentation and debugging an API response. Compact JSON removes every unnecessary space and line break, which makes payloads smaller for storage and network transfer. Both forms contain exactly the same data.

Your data stays in your browser

The formatter runs entirely on your device. The JSON you paste is not uploaded to our servers, so you can safely format responses that contain internal data. See the privacy policy for details.

Related tools

• XML Formatter to indent and check XML documents.
• Excel to JSON to turn any sheet of a spreadsheet into an array of objects.
• JSON to Excel to export an array of objects as a spreadsheet.
• Timestamp Converter to read the Unix timestamps often found in API responses.

Frequently asked questions

Why does valid JavaScript fail here?

A JavaScript object literal can use unquoted keys, single quotes, trailing commas and comments. JSON allows none of these. Remove them and the input will validate.

Does the formatter sort or change my keys?

It does not sort them, with one exception: keys that look like whole numbers are placed first, in numeric order, because that is how JavaScript engines store object keys. If the same key appears twice in one object, only the last value is kept.

Is there a size limit?

There is no fixed limit. Because formatting happens in your browser, very large documents, typically tens of megabytes, depend on your device's memory and may take a moment.