Build Status

JSON 3 is a modern JSON implementation compatible with a variety of JavaScript platforms, including Internet Explorer 6, Opera 7, Safari 2, and Netscape 6. The current version is 3.3.2.

Special thanks to cdnjs and jsDelivr for hosting CDN copies of JSON 3.

JSON is a language-independent data interchange format based on a loose subset of the JavaScript grammar. Originally popularized by Douglas Crockford, the format was standardized in the fifth edition of the ECMAScript specification. The 5.1 edition, ratified in June 2011, incorporates several modifications to the grammar pertaining to the serialization of dates.

JSON 3 exposes two functions: stringify() for serializing a JavaScript value to JSON, and parse() for producing a JavaScript value from a JSON source string. It is a drop-in replacement for JSON 2. The functions behave exactly as described in the ECMAScript spec, except for the date serialization discrepancy noted below.

The JSON 3 parser does not use eval or regular expressions. This provides security and performance benefits in obsolete and mobile environments, where the margin is particularly significant. The complete benchmark suite is available on jsPerf.

The project is hosted on GitHub, along with the unit tests. It is part of the BestieJS family, a collection of best-in-class JavaScript libraries that promote cross-platform support, specification precedents, unit testing, and plenty of documentation.

Changes from JSON 2


As of v3.2.3, JSON 3 is compatible with Prototype 1.6.1 and older.

In contrast to JSON 2, JSON 3 does not

Date Serialization

JSON 3 deviates from the specification in one important way: it does not define Date#toISOString() or Date#toJSON(). This preserves CommonJS compatibility and avoids polluting native prototypes. Instead, date serialization is performed internally by the stringify() implementation: if a date object does not define a custom toJSON() method, it is serialized as a simplified ISO 8601 date-time string.

Several native Date#toJSON() implementations produce date time strings that do not conform to the grammar outlined in the spec. For instance, all versions of Safari 4, as well as JSON 2, fail to serialize extended years correctly. Furthermore, JSON 2 and older implementations omit the milliseconds from the date-time string (optional in ES 5, but required in 5.1). Finally, in all versions of Safari 4 and 5, serializing an invalid date will produce the string "Invalid Date", rather than null. Because these environments exhibit other serialization bugs, however, JSON 3 will override the native stringify() implementation.

Portions of the date serialization code are adapted from the date-shim project.


Web Browsers

<script src="//cdnjs.cloudflare.com/ajax/libs/json3/3.3.2/json3.min.js"></script>
  JSON.stringify({"Hello": 123});
  // => '{"Hello":123}'
  JSON.parse("[[1, 2, 3], 1, 2, 3, 4]", function (key, value) {
    if (typeof value == "number") {
      value = value % 2 ? "Odd" : "Even";
    return value;
  // => [["Odd", "Even", "Odd"], "Odd", "Even", "Odd", "Even"]

When used in a web browser, JSON 3 exposes an additional JSON3 object containing the noConflict() and runInContext() functions, as well as aliases to the stringify() and parse() functions.

noConflict and runInContext

Asynchronous Module Loaders

JSON 3 is defined as an anonymous module for compatibility with RequireJS, curl.js, and other asynchronous module loaders.

<script src="//cdnjs.cloudflare.com/ajax/libs/require.js/2.1.10/require.js"></script>
    "paths": {
      "json3": "./path/to/json3"
  }, ["json3"], function (JSON) {
    JSON.parse("[1, 2, 3]");
    // => [1, 2, 3]

To avoid issues with third-party scripts, JSON 3 is exported to the global scope even when used with a module loader. If this behavior is undesired, JSON3.noConflict() can be used to restore the global JSON object to its original value.

Note: If you intend to use JSON3 alongside another module, please do not simply concatenate these modules together, as that would cause multiple define calls in one script, resulting in errors in AMD loaders. The r.js build optimiser can be used instead if you need a single compressed file for production.

CommonJS Environments

var JSON3 = require("./path/to/json3");
JSON3.parse("[1, 2, 3]");
// => [1, 2, 3]

JavaScript Engines

JSON.stringify({"Hello": 123, "Good-bye": 456}, ["Hello"], "\t");
// => '{\n\t"Hello": 123\n}'


JSON 3 has been tested with the following web browsers, CommonJS environments, and JavaScript engines.

Web Browsers

CommonJS Environments

JavaScript Engines

Known Incompatibilities

Required Native Methods

JSON 3 assumes that the following methods exist and function as described in the ECMAScript specification:


Check out a working copy of the JSON 3 source code with Git:

$ git clone git://github.com/bestiejs/json3.git
$ cd json3

If you’d like to contribute a feature or bug fix, you can fork JSON 3, commit your changes, and send a pull request. Please make sure to update the unit tests in the test directory as well.

Alternatively, you can use the GitHub issue tracker to submit bug reports, feature requests, and questions, or send tweets to @kitcambridge and @demoneaux.

JSON 3 is released under the MIT License.