Request-Response Cycle, Headers, Payloads, and JSON Basics
Understand what actually travels between client and server in a RESTful API and how requests and responses are structured.
Inside this chapter
- What a Request Contains
- What a Response Contains
- JSON as the Common Data Format
- Important Headers
- Business Example
Series navigation
Study the chapters in order for the clearest path from REST basics to advanced API design, operations, and production readiness. Use the navigation at the bottom to move smoothly across the full tutorial series.
What a Request Contains
An HTTP request typically includes a method, URL, headers, optional query parameters, and sometimes a body. The body usually carries data for create or update operations, while headers provide metadata such as authentication tokens, content type, and caching rules.
What a Response Contains
An HTTP response usually contains a status code, headers, and a body. The body may return JSON data, error details, an empty success response, or sometimes files and binary content.
JSON as the Common Data Format
{
"id": 42,
"name": "Asha",
"email": "asha@example.com"
}JSON is widely used because it is language-neutral, human-readable, and easy for browsers, mobile apps, and backend services to parse.
Important Headers
Content-Typeindicates the body format, such asapplication/jsonAuthorizationcarries auth credentials or bearer tokensAccepttells the server what response format the client expectsCache-Controlinfluences caching behavior
Business Example
A mobile banking app may send a POST request with JSON body data to transfer funds, include an authorization token in the header, and receive a JSON response containing transaction status, timestamps, and reference numbers.