# What is HTTP

Quick Reference: TCP vs UDP | WebSockets

# Quick Reference

# Clear Definition

HTTP (HyperText Transfer Protocol) is the foundation of data communication on the web. It's a request-response protocol that enables clients to fetch resources from servers.

💡 Key Insight: HTTP is stateless, meaning each request is independent. State is maintained through cookies, sessions, or tokens.

# Core Concepts

# HTTP Methods

• GET: Retrieve data (idempotent, safe)
• POST: Create data (not idempotent)
• PUT: Update/replace data (idempotent)
• PATCH: Partial update (not idempotent)
• DELETE: Delete data (idempotent)

# HTTP Status Codes

• 2xx Success: 200 OK, 201 Created, 204 No Content
• 3xx Redirection: 301 Moved, 304 Not Modified
• 4xx Client Error: 400 Bad Request, 401 Unauthorized, 404 Not Found
• 5xx Server Error: 500 Internal Error, 503 Service Unavailable

# HTTP/2 Features

• Multiplexing: Multiple requests over single connection
• Header Compression: HPACK compression
• Server Push: Server can push resources proactively
• Binary Protocol: More efficient than text-based HTTP/1.1

# HTTP/3 Features

• QUIC Protocol: Built on UDP instead of TCP
• Faster Connection: Reduced handshake time
• Better Multiplexing: Improved over HTTP/2
• Connection Migration: Handles network changes better

# Best Practices

1. Use Appropriate Methods: GET for reads, POST for creates
2. Proper Status Codes: Return correct status codes
3. Idempotency: Make operations idempotent when possible
4. Caching: Use appropriate cache headers

# Quick Reference Summary

HTTP: Request-response protocol for web communication. Stateless, uses TCP.

HTTP/2: Multiplexing, header compression, server push. Better performance.

HTTP/3: Built on QUIC (UDP), faster connections, better performance.

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