Which is Better Data Serialization Formats?
json5 vs yaml vs toml vs hjson
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What's Data Serialization Formats?

Data serialization formats are essential in web development for configuration files, data interchange, and APIs. They allow developers to represent complex data structures in a human-readable format, making it easier to manage and manipulate data. Each of these formats has unique features that cater to different needs, from simplicity and readability to support for complex data types. Choosing the right format can significantly impact the ease of development, maintenance, and performance of applications.

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json576,903,9046,499235 kB33-MIT
yaml52,417,2011,277681 kB189 days agoISC
toml1,275,160306-206 years agoMIT
hjson204,920414-214 years agoMIT
Feature Comparison: json5 vs yaml vs toml vs hjson

Readability

  • json5: JSON5 improves upon JSON by allowing comments and more flexible syntax, making it easier for developers to document their configurations directly within the files, enhancing readability without sacrificing structure.
  • yaml: YAML is known for its readability, using indentation to represent structure, which makes it visually appealing and easy to understand. It supports complex data structures while remaining accessible.
  • toml: TOML emphasizes simplicity and clarity, using a clear key-value pair structure that is easy to read and write. Its design is focused on being straightforward, making it ideal for configuration files.
  • hjson: HJSON is designed for human readability, allowing comments and a more relaxed syntax. This makes it easier for users to understand and edit configuration files without worrying about strict formatting rules.

Syntax Flexibility

  • json5: JSON5 extends JSON by allowing trailing commas, unquoted keys, and multi-line strings, providing a more forgiving syntax that can accommodate different coding styles and preferences.
  • yaml: YAML's syntax is highly flexible, allowing for both block and inline styles, as well as the use of anchors and references to reduce redundancy. This flexibility is beneficial for complex configurations.
  • toml: TOML uses a straightforward syntax that is easy to parse, with support for various data types like arrays and tables. It maintains a balance between simplicity and expressiveness, making it versatile for configuration needs.
  • hjson: HJSON allows for a more lenient syntax compared to JSON, enabling features like unquoted strings and trailing commas. This flexibility reduces the likelihood of syntax errors, especially for non-technical users.

Data Structure Support

  • json5: JSON5 supports all standard JSON data types and adds flexibility with comments and trailing commas, making it a good choice for configurations that require a mix of data types.
  • yaml: YAML excels in representing complex data structures, including nested dictionaries and lists, making it suitable for configurations that need to capture intricate relationships between data.
  • toml: TOML is designed for hierarchical data structures, supporting tables, arrays, and nested tables, which makes it ideal for configuration files that require organization and clarity.
  • hjson: HJSON supports basic data structures like objects and arrays, making it suitable for simple configurations. It does not support complex types as extensively as other formats.

Use Cases

  • json5: JSON5 is a great choice for JavaScript applications that require configuration files, as it maintains compatibility with JSON while providing additional flexibility.
  • yaml: YAML is commonly used in configuration files for applications and services, such as Docker and Kubernetes, due to its ability to represent complex data structures and its readability.
  • toml: TOML is widely used in configuration files for applications, especially in the Rust ecosystem, due to its simplicity and clear structure, making it easy to manage settings.
  • hjson: HJSON is particularly useful for configuration files where human readability is a priority, such as in projects where non-developers may need to edit settings.

Community and Ecosystem

  • json5: JSON5 benefits from a supportive community and is often used in JavaScript projects, making it a popular choice among developers familiar with JSON.
  • yaml: YAML has a large and active community, with extensive support across various programming languages and frameworks, making it a well-established choice for configuration and data serialization.
  • toml: TOML has gained traction in the Rust community and is increasingly adopted in other programming environments, supported by a growing ecosystem of libraries and tools.
  • hjson: HJSON has a smaller community compared to others but is appreciated for its simplicity and ease of use, especially in specific use cases like configuration files.
How to Choose: json5 vs yaml vs toml vs hjson
  • json5: Select JSON5 if you want to extend JSON with additional features like comments, trailing commas, and more flexible syntax, while still maintaining a close relationship with standard JSON.
  • yaml: Use YAML if you require a highly readable format that supports complex data structures, including lists and dictionaries, and if you need features like anchors and references to avoid duplication.
  • toml: Opt for TOML if you prefer a clear and simple configuration format that is easy to read and write, especially for hierarchical data, making it suitable for configuration files in applications.
  • hjson: Choose HJSON if you need a more human-friendly JSON format that allows comments and is less strict about syntax, making it easier for non-developers to read and write configuration files.
Similar Npm Packages to json5

json5 is a JavaScript library that extends JSON (JavaScript Object Notation) to make it more human-friendly and easier to work with. It allows for comments, trailing commas, and unquoted property names, which can simplify the process of writing and maintaining configuration files or data structures. This flexibility makes json5 a popular choice for developers who want a more readable format than standard JSON while still retaining compatibility with JavaScript.

However, there are several alternatives to json5, each with its own strengths:

  • toml is a configuration file format that is designed to be easy to read and write due to its clear syntax. It is particularly popular in the Rust ecosystem but has gained traction in other programming languages as well. Toml supports hierarchical data structures and is often used for configuration files in applications. If you need a format that is both human-readable and supports complex data types, toml is a great choice.
  • xml-js is a library that allows you to convert XML to JavaScript objects and vice versa. XML (eXtensible Markup Language) is widely used for data interchange, especially in web services and configuration files. While XML can be verbose and complex, xml-js simplifies the process of working with XML in JavaScript applications. If your project involves XML data, using xml-js can help you seamlessly integrate it with your JavaScript code.
  • yaml is another human-friendly data serialization format that is often used for configuration files. YAML (YAML Ain't Markup Language) is known for its readability and ability to represent complex data structures in a concise manner. It supports comments and is widely used in various applications, including Docker and Kubernetes configurations. If you are looking for a format that balances readability and complexity, YAML is an excellent alternative.

To see how json5 compares with toml, xml-js, and yaml, check out the comparison: Comparing json5 vs toml vs xml-js vs yaml.

Similar Npm Packages to yaml

yaml is a JavaScript library for parsing and stringifying YAML (YAML Ain't Markup Language) data. It provides a straightforward way to work with YAML files in Node.js and browser environments, making it easier for developers to read and write configuration files, data exchange formats, and more. While yaml is a robust option for handling YAML data, there are other libraries available that serve similar purposes. Here are a couple of alternatives:

  • js-yaml is a widely used library for parsing and dumping YAML in JavaScript. It is known for its simplicity and ease of use, making it a popular choice among developers. js-yaml supports both Node.js and browser environments and offers features such as custom type handling and support for complex data structures. If you need a reliable and well-documented library for working with YAML in your JavaScript projects, js-yaml is an excellent option.
  • yamljs is another library for parsing and stringifying YAML in JavaScript. It is lightweight and designed to be easy to use, making it suitable for projects that require basic YAML functionality without the overhead of more complex libraries. yamljs allows you to convert YAML to JavaScript objects and vice versa, making it a good choice for simple applications or scripts that need to handle YAML data.

To compare these libraries, check out the following link: Comparing js-yaml vs yaml vs yamljs.

Similar Npm Packages to hjson

hjson is a human-friendly JSON format that aims to make JSON more readable and writable for humans. It allows for comments, flexible syntax, and a more relaxed structure compared to standard JSON, making it easier to work with, especially for configuration files. Hjson is particularly useful in scenarios where configuration files need to be edited by non-developers or when readability is a priority.

While Hjson provides a unique approach to data serialization, there are several alternatives that also offer human-readable formats. Here are a few notable options:

  • json5 is an extension of JSON that allows for a more flexible syntax, including comments, trailing commas, and unquoted property names. It is designed to be a superset of JSON, making it easy to parse JSON5 data using existing JSON parsers. If you need a format that retains the structure of JSON while allowing for more human-friendly features, JSON5 is an excellent choice.
  • toml is a configuration file format that is designed to be easy to read due to its clear semantics. It uses a simple key-value pair structure and supports nested tables, arrays, and comments. TOML is often favored for configuration files in projects where clarity and simplicity are paramount. If you are looking for a format that is both human-readable and easy to parse, TOML is a strong candidate.
  • yaml (YAML Ain't Markup Language) is a human-readable data serialization format that is often used for configuration files and data exchange between languages. YAML supports complex data structures, including lists and dictionaries, and allows for comments, making it a versatile choice for many applications. If you need a format that can handle complex data structures while remaining readable, YAML is a popular and powerful option.

To explore how Hjson compares with JSON5, TOML, and YAML, check out the comparison: Comparing hjson vs json5 vs toml vs yaml.

README for json5

JSON5 – JSON for Humans

Build 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 strict 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.

Summary of Features

The following ECMAScript 5.1 features, which are not supported in JSON, have been extended to JSON5.

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.

Example

Kitchen-sink 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

For a detailed explanation of the JSON5 format, please read the official specification.

Installation and Usage

Node.js

npm install json5

CommonJS

const JSON5 = require('json5')

Modules

import JSON5 from 'json5'

Browsers

UMD

<!-- This will create a global `JSON5` variable. -->
<script src="https://unpkg.com/json5@2/dist/index.min.js"></script>

Modules

<script type="module">
  import JSON5 from 'https://unpkg.com/json5@2/dist/index.min.mjs'
</script>

API

The JSON5 API is compatible with the JSON API.

JSON5.parse()

Parses a JSON5 string, constructing the JavaScript value or object described by the string. An optional reviver function can be provided to perform a transformation on the resulting object before it is returned.

Syntax

JSON5.parse(text[, reviver])

Parameters

  • text: The string to parse as JSON5.
  • reviver: If a function, this prescribes how the value originally produced by parsing is transformed, before being returned.

Return value

The object corresponding to the given JSON5 text.

JSON5.stringify()

Converts a JavaScript value to a JSON5 string, optionally replacing values if a replacer function is specified, or optionally including only the specified properties if a replacer array is specified.

Syntax

JSON5.stringify(value[, replacer[, space]])
JSON5.stringify(value[, options])

Parameters

  • value: The value to convert to a JSON5 string.
  • replacer: A function that alters the behavior of the stringification process, or an array of String and Number objects that serve as a whitelist for selecting/filtering the properties of the value object to be included in the JSON5 string. If this value is null or not provided, all properties of the object are included in the resulting JSON5 string.
  • space: A String or Number object that's used to insert white space into the output JSON5 string for readability purposes. If this is a Number, it indicates the number of space characters to use as white space; this number is capped at 10 (if it is greater, the value is just 10). Values less than 1 indicate that no space should be used. If this is a String, the string (or the first 10 characters of the string, if it's longer than that) is used as white space. If this parameter is not provided (or is null), no white space is used. If white space is used, trailing commas will be used in objects and arrays.
  • options: An object with the following properties:
    • replacer: Same as the replacer parameter.
    • space: Same as the space parameter.
    • quote: A String representing the quote character to use when serializing strings.

Return value

A JSON5 string representing the value.

Node.js require() JSON5 files

When using Node.js, you can require() JSON5 files by adding the following statement.

require('json5/lib/register')

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

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

CLI

Since JSON is more widely used than JSON5, this package includes a CLI for converting JSON5 to JSON and for validating the syntax of JSON5 documents.

Installation

npm install --global json5

Usage

json5 [options] <file>

If <file> 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 lint before submitting pull requests. Please use an editor that supports EditorConfig.

Issues

To report bugs or request features regarding the JSON5 data format, please submit an issue to the official specification repository.

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

To report a security vulnerability, please follow the follow the guidelines described in our security policy.

License

MIT. See LICENSE.md for details.

Credits

Aseem Kishore founded this project. He wrote a blog post about the journey and lessons learned 10 years in.

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.

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.

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