JSON Syntax Rules

JSON syntax is a subset of the JavaScript object notation syntax. It is much stricter than standard JavaScript objects, and failure to follow even one small rule (like a missing comma or a single quote) will result in a parsing error.

Interactive Syntax Validator

Try writing some JSON below. Click "Validate" to check if it follows the strict rules:

1. Name/Value Pairs

JSON data is written as name/value pairs. A name/value pair consists of a field name (in double quotes), followed by a colon, followed by a value.

"firstName": "John"

2. Separation by Commas

Every name/value pair in an object must be separated by a comma (,). However, **do not** place a comma after the last pair.

{
  "city": "New York",
  "zip": 10001
}

3. Objects vs. Arrays

Valid Data Types

A JSON value can be:

• A string (must use double quotes)
• A number (no quotes)
• An object
• An array
• A boolean (true/false)
• null

Invalid Data Types

You cannot use the following in standard JSON:

• Functions
• Dates (Must be stored as strings)
• Undefined

JSON Files & MIME Type

• The file extension for JSON files is .json
• The MIME type for JSON text is application/json

Key Points to Remember

• Curly braces hold objects.
• Square brackets hold arrays.
• Double quotes are required for names and strings.
• Colons : separate names from values.
• Commas , separate items.
• JSON is case-sensitive.