Does JSON allow comments?

Standard JSON does not allow comments. Lines starting with // or /* */ will cause JSON.parse to fail. Remove comments or use a tool that strips them before parsing.

Why does JSON.parse fail on trailing commas?

The JSON specification does not permit a trailing comma after the last item in an object or array. JavaScript object literals often allow trailing commas, but JSON.parse follows strict JSON rules.

Can I use single quotes for JSON strings?

No. JSON requires double quotes around keys and string values. Single quotes are valid in JavaScript literals but are not valid in JSON.

Is JSON the same as a JavaScript object?

JSON is a text format. When you parse JSON you get JavaScript values (objects, arrays, strings, numbers, booleans, or null). Object literals in JavaScript can include unquoted keys, trailing commas, undefined, functions, and more—those are not valid in JSON.

JSON Formatter and Validator

Pretty-print with a 2-space indent, minify, or validate JSON using JSON.parse and JSON.stringify. Your data stays in the browser.

JSON input

Output

What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based way to exchange data. It uses objects ({ }) made of comma-separated key-value pairs, arrays ([ ]), strings in double quotes, numbers, booleans (true / false), and null.

JSON is the default format for many REST APIs and configuration files because it is easy for humans to read and for programs to parse. Browsers and servers often send JSON in HTTP request and response bodies.

Common JSON errors

Trailing commas — A comma after the last property or array element is invalid in JSON. Remove it or let your editor flag it.
Unquoted keys — Keys must be double-quoted strings. { name: "Ada" } is JavaScript; JSON requires "name".
Single quotes — JSON strings and keys use double quotes only. Single-quoted strings will not parse.

JSON vs JavaScript objects

JSON is a serialization format: a string that follows strict rules. A JavaScript object literal is syntax in source code; it can include features JSON does not allow.

JSON has no undefined, functions, or Symbol keys.
JSON does not allow comments or trailing commas.
JSON.parse(text) turns valid JSON text into JavaScript values; JSON.stringify(value) turns supported values into JSON text.

FAQ

Does JSON allow comments?: No. Standard JSON has no line or block comments. JSON.parse will throw if it sees // or /* */.
Why does JSON.parse fail on trailing commas?: The JSON grammar does not allow a comma after the final entry in an object or array. Many JavaScript engines accept trailing commas in object literals, but JSON is stricter.
Can I use single quotes for JSON strings?: No. Keys and string values must use double quotes. Single quotes are a common mistake when copying from informal JavaScript examples.
Is JSON the same as a JavaScript object?: JSON is text. After parsing, you get ordinary JavaScript values. Object literals in code can include syntax and values that are not valid in JSON.

JSON format, minify, and validate

What is JSON?

Common JSON errors

JSON vs JavaScript objects

FAQ

Related tools