HTTP Fundamentals

What is HTTP?

HTTP (HyperText Transfer Protocol) is the foundation of data communication on the World Wide Web. Every time you load a webpage, submit a form, or call an API, you are using HTTP.

HTTP Request Structure

Every HTTP request has three parts:

• Request Line — Method, URL, and HTTP version (e.g., GET /api/users HTTP/1.1)
• Headers — Key-value metadata like Content-Type, Authorization, Accept
• Body — Optional data payload (only in POST, PUT, PATCH)

HTTP Methods

• GET — Retrieve data. Should never modify anything.
• POST — Create a new resource.
• PUT — Fully replace a resource.
• PATCH — Partially update a resource.
• DELETE — Remove a resource.

bash
# GET request — fetch all users
curl -X GET https://api.example.com/users

# POST request — create a new user
curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name": "Shark", "email": "shark@javashark.in"}'

HTTP Status Codes

Status codes tell you what happened on the server:

• 2xx — Success → 200 OK, 201 Created, 204 No Content
• 3xx — Redirection → 301 Moved Permanently, 302 Found
• 4xx — Client Error → 400 Bad Request, 401 Unauthorized, 404 Not Found
• 5xx — Server Error → 500 Internal Server Error, 503 Service Unavailable

Summary

HTTP is the backbone of the web. As a backend developer, you will design and consume HTTP APIs every single day. Mastering HTTP methods, status codes, headers, and request/response cycles is non-negotiable.