As the digital world continues to expand, the volume of data exchanged between systems—many of which are unfamiliar with each other—grows exponentially. The format in which this data is stored and transmitted is crucial. Early on, XML (eXtensible Markup Language) gained popularity due to its resemblance to HTML, the backbone of the web. However, XML proved to be bulky and complex.

Enter JSON (JavaScript Object Notation), a lightweight, text-based, language-independent data interchange format that has become the de facto standard for web applications. Understanding JSON is fundamental for modern web development.

In this guide, we'll explore what JSON is, how it looks, how to use it in web applications and APIs, compare it with other data formats like XML and YAML, and delve into advanced topics like BSON and JSON Web Tokens (JWT).

What Is JSON?

JSON is a human-readable format for structuring data. It is used primarily to transmit data between a server and web application, serving as an alternative to XML. JSON is built on two structures:

1. A collection of name/value pairs: In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array.
2. An ordered list of values: In most languages, this is realized as an array, vector, list, or sequence.

Because of its simplicity and compatibility with JavaScript, JSON has become a ubiquitous data format for web applications.

JSON Syntax: What Does JSON Look Like?

At its core, JSON is composed of key/value pairs, where the key is a string and the value can be a string, number, object, array, boolean, or null. The data is enclosed within curly braces {} for objects and square brackets [] for arrays.