HTTP Fundamentals: The Backbone of Web Communication

September 6, 20255 min read
HTTP (HyperText Transfer Protocol) is the foundation of data communication on the web. It's a request-response protocol between clients and servers.

Basic Flow

HTTP Request Structure

Example Request:

GET /products?category=books HTTP/1.1
Host: api.store.com
User-Agent: Mozilla/5.0
Accept: application/json
Authorization: Bearer token123

HTTP Response Structure

Example Response:

HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: 52
Set-Cookie: sessionId=abc123

{"id": 1, "name": "JavaScript Book", "price": 29.99}

Common HTTP Methods

Real Examples:

  • GET /users/123 - Fetch user with ID 123
  • POST /users - Create new user
  • PUT /users/123 - Replace user 123 entirely
  • PATCH /users/123 - Update user's email only
  • DELETE /users/123 - Delete user 123

Status Codes

HTTP Headers Categories

Connection Lifecycle

HTTP vs HTTPS

Key Differences:

  • HTTP: Port 80, unencrypted, vulnerable to MITM attacks
  • HTTPS: Port 443, TLS/SSL encrypted, secure communication

Request-Response Example Flow

Caching Mechanism

Common Headers Explained

Request Headers:

  • Host: example.com - Target server
  • User-Agent: Browser/client identification
  • Accept: text/html,application/json - Preferred response formats
  • Authorization: Bearer token123 - Authentication
  • Cookie: sessionId=abc - Client state

Response Headers:

  • Content-Type: application/json - Response format
  • Set-Cookie: sessionId=xyz - State to store
  • Cache-Control: max-age=3600 - Caching rules
  • Location: /new-path - Redirect destination

HTTP/2 vs HTTP/1.1

HTTP/2 Advantages:

  • Multiplexing (parallel requests)
  • Server push
  • Header compression
  • Binary protocol

REST API Example

Error Handling Flow

Key Concepts Summary

  1. Stateless Protocol: Each request is independent
  2. Text-based: Human-readable format (HTTP/1.1)
  3. Request-Response: Client initiates, server responds
  4. Methods: Define action type (GET, POST, etc.)
  5. Status Codes: Indicate result (200, 404, 500, etc.)
  6. Headers: Metadata about request/response
  7. Body: Actual data being transferred
  8. Caching: Reduce server load and latency
  9. Security: HTTPS adds encryption layer
  10. Versions: HTTP/1.1 → HTTP/2 → HTTP/3 (QUIC)