What is JSON? Complete Guide for Beginners []

What Does JSON Stand For?

JSON stands for "JavaScript Object Notation." Despite the name, JSON is completely language-independent and works with almost all programming languages including Python, Java, C#, PHP, Ruby, Go, and many more.

JSON was created by Douglas Crockford in 2001. The first JSON message was sent in April 2001, and the format quickly gained popularity as a lightweight alternative to XML for data exchange. Today, JSON is standardized in two specifications:

• RFC 8259 – Published by IETF in December 2017, the current Internet Standard
• ECMA-404 – Published by Ecma International in October 2013

What Coding Language Does JSON Use?

JSON is not tied to any specific programming language. While it was derived from JavaScript syntax, JSON is a text format that any language can parse and generate. It's language-independent by design.

Most modern programming languages have built-in or standard library support for JSON:

Is JSON Python or Java?

JSON is neither Python nor Java—it's a data format, not a programming language. JSON was derived from JavaScript syntax but is completely language-independent. Both Python and Java (and virtually all other programming languages) can read and write JSON data.

Think of JSON like a common language for data: just as English might be used as a common language between people who speak different native languages, JSON is a common format for exchanging data between programs written in different programming languages.

JSON Syntax Basics

JSON syntax is simple and consists of just two structures: objects and arrays.

Objects (Key-Value Pairs)

Objects are wrapped in curly braces {} and contain key-value pairs:

{
  "name": "John Doe",
  "age": 30,
  "isActive": true
}

Arrays (Ordered Lists)

Arrays are wrapped in square brackets [] and contain ordered values:

{
  "fruits": ["apple", "banana", "orange"],
  "numbers": [1, 2, 3, 4, 5]
}

Data Types

JSON supports six data types:

• String – Text in double quotes: "hello"
• Number – Integer or decimal: 42, 3.14
• Boolean – true or false
• Null – Empty value: null
• Object – Nested {} structure
• Array – Nested [] structure

Nested Structures

Objects and arrays can be nested to create complex data structures:

{
  "person": {
    "name": "Jane Smith",
    "address": {
      "street": "123 Main St",
      "city": "New York"
    },
    "phones": [
      {"type": "home", "number": "555-1234"},
      {"type": "work", "number": "555-5678"}
    ]
  }
}

What Does {} Mean in JSON?

Curly braces {} in JSON represent an object (also called a dictionary, map, or hash in other languages). An object contains zero or more key-value pairs.

Each key-value pair follows these rules:

• The key must be a string in double quotes
• A colon : separates the key from the value
• The value can be any valid JSON data type
• Multiple pairs are separated by commas ,

{
  "key1": "value1",
  "key2": 42,
  "key3": true,
  "key4": null,
  "key5": {"nested": "object"},
  "key6": [1, 2, 3]
}

Similarly, square brackets [] represent an array—an ordered list of values separated by commas.

What is Not Allowed in JSON?

JSON has strict syntax rules designed to keep it simple and fast to parse. Here's what's not allowed:

Is JSON Binary or Text?

JSON is a text-based format, not binary. It's stored and transmitted as human-readable text, typically encoded in UTF-8 (which RFC 8259 mandates for network transmission).

This text-based nature has trade-offs:

• Advantages: Easy to read, debug, and edit by humans
• Disadvantages: Larger file sizes and slower parsing than binary formats

For applications requiring better performance or smaller sizes, binary alternatives include:

• MessagePack – Binary JSON-like format
• Protocol Buffers – Google's binary format
• BSON – Binary JSON used by MongoDB

For binary data within JSON (like images), use Base64 encoding to represent binary as a text string.

JSON Example

Here's a complete, real-world JSON example—a typical API response:

{
  "status": "success",
  "data": {
    "user": {
      "id": 12345,
      "username": "johndoe",
      "email": "[email protected]",
      "isVerified": true,
      "createdAt": "2025-01-15T10:30:00Z",
      "profile": {
        "firstName": "John",
        "lastName": "Doe",
        "avatar": "https://example.com/avatar.jpg",
        "bio": null
      },
      "roles": ["user", "moderator"],
      "settings": {
        "notifications": true,
        "theme": "dark",
        "language": "en"
      }
    }
  },
  "meta": {
    "requestId": "abc-123-xyz",
    "responseTime": 42
  }
}

This example demonstrates objects, arrays, strings, numbers, booleans, null values, and nested structures.

What is JSON Used For?

JSON is used wherever structured data needs to be stored or transmitted. Common use cases include:

• Web APIs (REST) – JSON is the standard format for REST API requests and responses, used by most web services.
• Configuration files – Many applications use JSON for settings (package.json, tsconfig.json, etc.).
• Data storage – NoSQL databases like MongoDB store data in JSON-like format (BSON).
• Data exchange – Sending data between client and server, between microservices, or between different systems.
• Browser storage – LocalStorage and SessionStorage APIs use JSON for persisting data in the browser.
• Logging – Structured logging often uses JSON for machine-parseable log entries.