What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data format used to store and exchange structured data. It is the universal language of web APIs — when your app talks to a server, the response almost always comes back as JSON.

JSON Syntax Rules

JSON has a simple, strict syntax with only a handful of rules:

• Data is written as key/value pairs — "key": "value"
• Keys must be double-quoted strings — single quotes are not valid
• Values can be string, number, boolean, null, object, or array
• Objects are wrapped in {}, arrays in []
• Items are separated by commas — no trailing comma after the last item
• No comments allowed (use JSONC if you need comments)

JSON Data Types

JSON Examples

A basic JSON object

{
  "name": "Alice Johnson",
  "age": 30,
  "isActive": true,
  "score": 98.5,
  "address": null,
  "tags": ["developer", "designer"],
  "contact": {
    "email": "alice@example.com",
    "phone": "+1-555-0100"
  }
}

A JSON array of objects

[
  { "id": 1, "product": "Laptop", "price": 999.99 },
  { "id": 2, "product": "Mouse",  "price": 29.99  },
  { "id": 3, "product": "Keyboard","price": 79.99 }
]

Deeply nested JSON

{
  "order": {
    "id": "ORD-2026-001",
    "customer": {
      "name": "Bob Smith",
      "tier": "premium"
    },
    "items": [
      { "sku": "LAP-001", "qty": 1, "price": 999.99 },
      { "sku": "MSE-042", "qty": 2, "price": 29.99 }
    ],
    "total": 1059.97,
    "shipped": false
  }
}

Common JSON Mistakes

{ 'name': 'Alice' }

{ "name": "Alice" }

{ name: "Alice" }

{ "name": "Alice" }

{ "tags": ["a", "b", ] }

{ "tags": ["a", "b"] }

{ "active": True }

{ "active": true }

// comment
{ "x": 1 }

{ "x": 1 }

{ "val": undefined }

{ "val": null }

Frequently Asked Questions

Work with JSON