HTTP/HTTPS - WebDevGuide

What is HTTP?

The foundation of data communication on the web

HTTP (HyperText Transfer Protocol) is the foundation of data communication on the World Wide Web. When you visit a website, your browser sends an HTTP request to a server, which processes it and sends back an HTTP response.

This request-response cycle is the core of how web applications work. Understanding it deeply will help you debug issues, optimize performance, and design better APIs.

Request-Response Cycle

How client and server communicate

HTTP Request-Response Flow

Watch how data flows between client and server

Client (Browser)

Request → ← Response

Server (Web Server)

Ready: Client is ready to make a request

HTTP Request

GET /api/users HTTP/1.1
Host: example.com
Accept: application/json
Authorization: Bearer token123
User-Agent: Mozilla/5.0

HTTP Response

HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: max-age=3600

{"users": [...]}

HTTP Methods

Different types of requests for different operations

CRUD Operations Mapping

Each method serves a specific purpose in RESTful APIs

Click on a method to see details

CRUD to HTTP Methods Mapping

Create

POST

Read

GET

Update

PUT / PATCH

Delete

DELETE

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Why does idempotency matter?

Idempotent methods are safe to retry. If a network error occurs, you can safely resend a GET, PUT, or DELETE request without causing duplicates. POST is not idempotent - retrying might create duplicate records.

Status Codes

Server responses categorized by meaning

1xx

Informational

2xx

Success

3xx

Redirection

4xx

Client Error

5xx

Server Error

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Common Interview Question

"What's the difference between 401 and 403?"
401 means "Who are you?" (authentication missing/invalid).
403 means "I know who you are, but you can't do this" (authorization failed).

Common Headers

Metadata that controls request and response behavior

Request Header

Response Header

Both

TLS/SSL Handshake

How HTTPS establishes a secure connection

The TLS Handshake Process

Before any HTTP data is sent, client and server establish encryption

Client

Client Hello

Server

Client Hello

Client sends supported TLS versions, cipher suites, and a random number

Asymmetric Encryption

Used during handshake. Public key encrypts, private key decrypts. Slower but secure for key exchange.

Symmetric Encryption

Used after handshake. Same key for encrypt/decrypt. Fast, efficient for data transfer.

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Why HTTPS Matters

• Encryption: Data cannot be read by eavesdroppers
• Authentication: Proves you're talking to the real server
• Integrity: Data cannot be modified in transit

Key Terms to Remember

Master these terms for technical interviews