JSON5 – JSON for Humans

![Build Status][Build Status] ![Coverage Status][Coverage Status]

JSON5 is an extension to the popular [JSON] file format that aims to be easier to write and maintain _by hand_ (e.g. for config files). It is _not intended_ to be used for machine-to-machine communication. (Keep using JSON or other file formats for that. 🙂)

JSON5 was started in 2012, and as of 2022, now gets >65M downloads/week, ranks in the top 0.1% of the most depended-upon packages on npm, and has been adopted by major projects like **Chromium, Next.js, Babel, Retool, WebStorm, and more**. It's also natively supported on Apple platforms like macOS and iOS.

Formally, the JSON5 Data Interchange Format is a superset of JSON (so valid JSON files will always be valid JSON5 files) that expands its syntax to include some productions from [ECMAScript 5.1] (ES5). It's also a _subset_ of ES5, so valid JSON5 files will always be valid ES5.*

This JavaScript library is a reference implementation for JSON5 parsing and serialization, and is directly used in many of the popular projects mentioned above (where e.g. extreme performance isn't necessary), but others have created many other libraries across many other platforms.

[Build Status]: https://app.travis-ci.com/json5/json5

[Coverage Status]: https://coveralls.io/github/json5/json5

[JSON]: https://tools.ietf.org/html/rfc7159

[ECMAScript 5.1]: https://www.ecma-international.org/ecma-262/5.1/

Summary of Features

Objects

• Object keys may be an ECMAScript 5.1 _[IdentifierName]_.
• Objects may have a single trailing comma.

Arrays

• Arrays may have a single trailing comma.

Strings

• Strings may be single quoted.
• Strings may span multiple lines by escaping new line characters.
• Strings may include character escapes.

Numbers

• Numbers may be hexadecimal.
• Numbers may have a leading or trailing decimal point.
• Numbers may be [IEEE 754] positive infinity, negative infinity, and NaN.
• Numbers may begin with an explicit plus sign.

Comments

• Single and multi-line comments are allowed.

White Space

• Additional white space characters are allowed.

[IEEE 754]: http://ieeexplore.ieee.org/servlet/opac?punumber=4610933

Example

{
  // comments
  unquoted: 'and you can quote me on that',
  singleQuotes: 'I can use "double quotes" here',
  lineBreaks: "Look, Mom! \
No \\n's!",
  hexadecimal: 0xdecaf,
  leadingDecimalPoint: .8675309, andTrailing: 8675309.,
  positiveSign: +1,
  trailingComma: 'in objects', andIn: ['arrays',],
  "backwardsCompatible": "with JSON",
}

A more real-world example is this config file from the Chromium/Blink project.

Specification

Installation and Usage

Node.js

npm install json5

CommonJS

const JSON5 = require('json5')
// or
const {parse, stringify} = require('json5')

Modules

import JSON5 from 'json5'
// or
import {parse, stringify} from 'json5'

require('json5') returns an object with parse and stringify. The ES module entry has parse and stringify as named exports, and the same object as its default export.

TypeScript

Browsers

Global object

<!-- This will create a global JSON5 variable. -->
<script src="https://unpkg.com/json5@3/dist/index.min.js"></script>

Modules

<script type="module">
  import JSON5 from 'https://unpkg.com/json5@3/dist/index.min.mjs'
</script>

API

[JSON API]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON

JSON5.parse()

Syntax

Parameters

• text: The string to parse as JSON5.
• reviver: If a function, this prescribes how the value originally produced by

Return value

JSON5.stringify()

Syntax

Parameters

• value: The value to convert to a JSON5 string.
• replacer: A function that alters the behavior of the stringification

• space: A String or Number object that's used to insert white space into the

• options: An object with the following properties:

Return value

Node.js require() JSON5 files

require('json5/register')

Then you can load a JSON5 file with a Node.js require() statement. For example:

const config = require('./config.json5')

CLI

Installation

npm install --global json5

Usage

json5 [options] <file>

If is not provided, then STDIN is used.

Options:

• -s, --space: The number of spaces to indent or t for tabs
• -o, --out-file [file]: Output to the specified file, otherwise STDOUT
• -v, --validate: Validate JSON5 but do not output JSON
• -V, --version: Output the version number
• -h, --help: Output usage information

Contributing

Development

git clone https://github.com/json5/json5
cd json5
npm install

When contributing code, please write relevant tests and run npm test and npm run test-types before submitting pull requests. Please use an editor that supports EditorConfig.

Issues

Note that we will never add any features that make JSON5 incompatible with ES5; that compatibility is a fundamental premise of JSON5.*

To report bugs or request features regarding this JavaScript implementation of JSON5, please submit an issue to _this_ repository.

Security Vulnerabilities and Disclosures

ECMAScript Compatibility

License

Credits

Michael Bolin independently arrived at and published some of these same ideas with awesome explanations and detail. Recommended reading: Suggested Improvements to JSON

Douglas Crockford of course designed and built JSON, but his state machine diagrams on the JSON website, as cheesy as it may sound, gave us motivation and confidence that building a new parser to implement these ideas was within reach! The original implementation of JSON5 was also modeled directly off of Doug’s open-source [json_parse.js] parser. We’re grateful for that clean and well-documented code.

[json_parse.js]: https://github.com/douglascrockford/JSON-js/blob/03157639c7a7cddd2e9f032537f346f1a87c0f6d/json_parse.js

Max Nanasy has been an early and prolific supporter, contributing multiple patches and ideas.

Andrew Eisenberg contributed the original stringify method.

Jordan Tucker has aligned JSON5 more closely with ES5, wrote the official JSON5 specification, completely rewrote the codebase from the ground up, and is actively maintaining this project.