JSON (JavaScript Object Notation)
JSON is a lightweight, text-based data format used to structure and exchange data between applications in a human-readable way.
What is JSON?
JavaScript Object Notation (JSON) is a data interchange format designed to be easy for humans to read and write, and easy for machines to parse and generate. Although inspired by JavaScript syntax, JSON is language-independent and widely supported across platforms. JSON is commonly used to transmit data between clients and servers, especially in web and API-based systems.
Why JSON matters
JSON is important because it:
- Is lightweight and efficient over networks
- Is easy to read, write, and debug
- Is supported by virtually all programming languages
- Fits naturally with web and cloud architectures
- Has become the de facto standard for APIs
Most modern applications rely on JSON for data exchange.
JSON structure
JSON represents data using two primary structures:
Objects are collections of key-value pairs where keys are strings and values can be various data types.
Arrays are ordered lists of values.
Supported value types include strings, numbers, booleans, objects, arrays, and null.
Example:
{
"user": "admin",
"user": "admin",
"active": true,
"roles": ["editor", "admin"]
}
Common JSON use cases
JSON is widely used for:
- REST and GraphQL API responses
- Configuration files
- Data exchange between services
- Web and mobile applications
- Headless CMS content delivery
- Logging and structured events
In many systems, JSON replaces older formats like XML.
JSON vs XML
| Aspect | JSON | XML |
|---|---|---|
| Readability | High | Lower |
| Size | Smaller | Larger |
| Parsing | Faster | Slower |
| Verbosity | Low | High |
| Schema enforcement | Optional | Strong |
JSON favors simplicity and performance over strict structure.
JSON and APIs
In API contexts:
- JSON is the default payload format
- Data is typically transmitted over HTTP/HTTPS
- Content type is
application/json - JSON works seamlessly with REST and GraphQL
Well-structured JSON improves API usability and performance.
JSON validation and schemas
To ensure consistency, JSON can be validated using:
- JSON Schema
- API specifications (OpenAPI)
- Application-level validation
Validation helps prevent malformed data and security issues.
Security considerations
While JSON itself is safe, risks arise from misuse:
- Injection attacks if data is not validated
- Excessive data exposure in API responses
- Insecure deserialization in some environments
- Logging sensitive data in JSON payloads
Input validation and least-privilege data exposure are critical.
Common misconceptions
- "JSON is a programming language"
- "JSON is only used with JavaScript"
- "JSON enforces a strict schema by default"
- "JSON is always secure"