Understanding HTTP, HTTPS, TCP & UDP — The Complete Beginner-Friendly Guide

New developers often get confused by the different network protocols—HTTP, HTTPS, TCP, and UDP. Even experienced engineers sometimes struggle to explain how these protocols work together when you “hit a URL” in the browser.

This guide simplifies everything with clear explanations and diagrams, and helps you understand how the internet really works.

1. Network Layers — The Foundation

The internet follows a layered architecture. You don’t need to memorize the full OSI model; you only need to remember three layers:


APPLICATION LAYER → HTTP, HTTPS, DNS, FTP
SECURITY LAYER    → TLS/SSL
TRANSPORT LAYER   → TCP, UDP
NETWORK LAYER     → IP (Routing)

Each layer has a specific job:

Application Layer: Defines how apps talk (HTTP/HTTPS)
Transport Layer: Moves data (TCP/UDP)
Network Layer: Finds the route (IP)

2. What Are HTTP and HTTPS? (Application Layer)

HTTP (HyperText Transfer Protocol)

Runs at the application layer
Used for web pages, APIs, etc.
Plain text (not encrypted)

HTTPS (HTTP Secure)

HTTP + TLS encryption
Also an application-layer protocol
Secures communication between client and server
Uses certificates & encryption
Protects from hacking, MITM attacks, data sniffing

💡 HTTPS does NOT replace TCP. It rides on top of TCP.

3. What Are TCP and UDP? (Transport Layer)

TCP (Transmission Control Protocol)

Transport-layer protocol
Reliable, ordered delivery
Guarantees delivery
Used by HTTP & HTTPS

UDP (User Datagram Protocol)

Transport-layer protocol
Very fast but not reliable
Packets may be lost or reordered

Transport-Layer Use Cases

Protocol	Used For
TCP	Websites, APIs, banking apps, file downloads
UDP	Video calls, gaming, streaming, DNS

4. How HTTPS and TCP Are Related

Many people get confused here.
So here is the correct relationship:

✔ HTTPS = Application layer

✔ TCP = Transport layer

HTTPS depends on TCP but operates at a higher layer.

🔥 Stack (Top to Bottom)


HTTPS (Application Layer)
TLS/SSL (Security Layer)
TCP (Transport Layer)
IP  (Network Layer)

HTTPS encrypts your data → TCP delivers it reliably → IP routes it → Internet works!

5. Diagram: How the Protocols Work Together


┌──────────────────────────────────────────┐
│        APPLICATION LAYER (HTTP/HTTPS)    │
│    Browser requests, API calls, HTML     │
└──────────────────────▲───────────────────┘
                       │ TLS Encryption
┌──────────────────────┴───────────────────┐
│        TRANSPORT LAYER (TCP / UDP)       │
│  TCP for reliability | UDP for speed     │
└──────────────────────▲───────────────────┘
                       │
┌──────────────────────┴───────────────────┐
│        NETWORK LAYER (IP Routing)        │
└──────────────────────────────────────────┘

6. What Happens When You Hit a URL? (Full Flow)

Example:


https://apple.com/store

Step 1 — DNS Lookup (Usually UDP)

Browser asks DNS server for the IP of apple.com.

Step 2 — TCP Handshake

Browser creates a reliable connection using TCP:


SYN → SYN-ACK → ACK

Step 3 — TLS/SSL Handshake (Only for HTTPS)

Browser verifies server certificates
Server proves identity
Encryption keys are exchanged

Step 4 — Send HTTPS Request

Encrypted HTTP request:


GET /store

Step 5 — Server Responds

Encrypted HTTP response:


200 OK
<html>...</html>

Step 6 — Browser Renders Page

This entire flow happens in milliseconds.

7. Quick Comparison Table

Feature	HTTP	HTTPS	TCP	UDP
Layer	Application	Application	Transport	Transport
Secure	❌	✔ (TLS)	❌	❌
Reliable	Depends on TCP	Depends on TCP	✔	❌
Use Case	Websites, APIs	Secure websites	Web, apps, API	Video, calls, DNS

8. Final Summary

HTTPS is an application-level protocol
TCP is a transport-level protocol
HTTPS uses TLS for encryption and TCP for transport
UDP is faster but unreliable (used for real-time apps)
When you hit a URL, the browser performs DNS → TCP → TLS → HTTPS

9. One-Line Summary


HTTPS = HTTP + TLS encryption (Application Layer)
TCP = Reliable transport (Transport Layer)
HTTPS runs on top of TCP

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