URLs, HTTP and HTTPS

01

Learning Objectives

Build a strong understanding of how Web resources are addressed and communicated.

🔗

Understand URLs

Identify the major parts of a URL and understand what each part represents.

🌐

Understand HTTP

Learn the purpose of HTTP and its request-response model.

📤

Understand Requests

Study methods, paths, headers and request bodies.

📥

Understand Responses

Learn status codes, response headers and response bodies.

🔐

Understand HTTPS

Understand TLS, certificates, confidentiality, integrity and authentication.

🚀

Compare HTTP Versions

Understand the major differences between HTTP/1.1, HTTP/2 and HTTP/3.

02

What Is a URL?

A URL identifies a resource and provides information about how to locate or access it.

A URL is a Uniform Resource Locator. It is the familiar web address used to access a resource.

A browser can use a URL to identify a web resource such as an HTML page, image, API endpoint, video, document or other network-accessible resource.

💡

Simple idea

A URL tells the client how to access something and where that resource is located.

03

Anatomy of a URL

Let's break a complete URL into its major components.

https://www.codebhavya.com/Web-Technologies/lesson.html?id=3#http

01

Scheme

https identifies the URL scheme used for the resource.

02

Host

www.codebhavya.com identifies the host.

03

Path

/Web-Technologies/lesson.html identifies the resource path.

04

Query

?id=3 supplies query parameters.

05

Fragment

#http identifies a location within the document.

04

URL Component Reference

Quickly review the role of each part.

Component	Example	Purpose
Scheme	https	Identifies the access scheme.
Host	www.example.com	Identifies the destination host.
Port	:443	Identifies a specific service endpoint when specified.
Path	/products/1	Identifies the requested resource path.
Query	?page=2	Carries query parameters.
Fragment	#details	Identifies a document fragment or location.

05

What Is HTTP?

HTTP is the core application-layer protocol used for Web communication.

HTTP stands for Hypertext Transfer Protocol.

It follows a client-server request/response model. A client such as a browser sends a request and the server sends a response.

HTTP is used for much more than HTML pages. It can carry images, scripts, videos, API data, form submissions and many other kinds of resources.

Remember: HTTP defines the communication semantics; HTML, CSS and JavaScript define the content, presentation and behavior of web pages.

06

HTTP Request and Response

Every HTTP exchange revolves around messages.

CLIENT → SERVER

HTTP Request

Method

↓

Target / Path

↓

Headers

↓

Optional Body

The client describes what it wants the server to do or retrieve.

SERVER → CLIENT

HTTP Response

Status Code

↓

Headers

↓

Optional Body

The server reports the result and can return data or a representation of the resource.

07

Anatomy of an HTTP Request

Here is a simplified HTTP/1.1-style representation that helps beginners understand the message.

GET /Web-Technologies/ HTTP/1.1
Host: codebhavya.com
Accept: text/html
User-Agent: Browser
Connection: keep-alive

01

Method

GET indicates the requested operation.

02

Target

The target identifies the resource being requested.

03

Headers

Headers carry additional metadata about the request.

04

Body

Some requests contain a body, such as many POST requests.

08

HTTP Request Methods

Methods communicate the intended operation.

📥

GET

Requests a representation of a resource.

RETRIEVE

📤

POST

Submits data to a resource and can cause server-side state changes.

SUBMIT

🔄

PUT

Replaces the current representation of a target resource with the request content.

REPLACE

🧩

PATCH

Applies a partial modification to a resource.

MODIFY

🗑️

DELETE

Requests deletion of the specified resource.

DELETE

ℹ️

HEAD

Requests headers corresponding to a GET response without the response body.

METADATA

⚙️

OPTIONS

Requests information about communication options available for a target resource.

OPTIONS

🔗

CONNECT

Establishes a tunnel to the server identified by the target resource.

TUNNEL

Placement Tip: Do not memorize HTTP methods without understanding their semantics. Interviewers often ask the difference between GET, POST, PUT, PATCH and DELETE.

09

Safe and Idempotent Methods

These terms describe important properties of HTTP methods.

Method	Safe	Idempotent	Basic Idea
GET	Yes	Yes	Retrieve a representation
HEAD	Yes	Yes	Retrieve headers
PUT	No	Yes	Replace target representation
DELETE	No	Yes	Delete target resource
POST	No	No	Submit/process data
PATCH	No	Depends on implementation	Partial modification

A method is called safe when its defined semantics are read-only from the client's perspective.

An idempotent method means that repeating the same request is intended to have the same effect on the server state as making it once, even though individual responses can differ.

10

Anatomy of an HTTP Response

A response tells the client what happened.

HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 1200
Cache-Control: max-age=3600

<html> ... </html>

01

Protocol Version

Identifies the HTTP version used for the response representation in this HTTP/1.x-style example.

02

Status Code

200 communicates successful completion.

03

Headers

Response headers provide additional metadata and processing instructions.

04

Body

The response body can contain HTML, JSON, text, media or other content.

11

HTTP Status Codes

The first digit tells you the broad class of response.

ℹ️

1xx

Informational responses.

INFORMATION

✅

2xx

Successful responses.

SUCCESS

↪️

3xx

Redirection responses.

REDIRECTION

⚠️

4xx

Client error responses.

CLIENT ERROR

COMMON RESPONSES

Frequently Seen Codes

200 — successful request

201 — resource created

204 — successful with no response content

301 — permanent redirection

302 — temporary redirection

ERROR RESPONSES

Common Error Codes

400 — bad request

401 — authentication required

403 — forbidden

404 — resource not found

500 — internal server error

503 — service unavailable

12

HTTP Headers

Headers carry additional information about requests and responses.

📦

Content-Type

Describes the media type of the content.

REPRESENTATION

📏

Content-Length

Communicates content length when applicable.

SIZE

🗃️

Cache-Control

Communicates caching behavior.

CACHE

🔑

Authorization

Carries credentials or authorization information in supported authentication schemes.

AUTH

Request and response headers are metadata associated with HTTP messages. They help clients and servers negotiate content, describe representations, control caching, communicate authentication details and more.

Important: A header is metadata. It is not the same thing as the main content carried in the message body.

13

Is HTTP Stateless?

HTTP itself does not automatically remember previous requests as application state.

📩

Request 1

Browser sends a request containing the information needed for that request.

GET /login

Request metadata

+

📩

Request 2

A later request needs its own information needed by the application.

GET /dashboard

State mechanisms may be included

💡

Then how do login systems work?

Applications can use mechanisms such as cookies, sessions and authorization tokens to associate multiple requests with application state.

14

HTTP/1.1, HTTP/2 and HTTP/3

HTTP has evolved while preserving the core HTTP semantics.

HTTP/1.1

Traditional Message Syntax

✔ Text-based HTTP message format

✔ Well-established request/response model

✔ Connection management features

HTTP/2

More Efficient Transport

✔ Binary framing

✔ Multiplexed exchanges

✔ Header compression

HTTP/3

HTTP over QUIC

✔ Uses QUIC

✔ Stream multiplexing

✔ Designed for lower-latency connection behavior

Important: HTTP/2 and HTTP/3 improve how HTTP communication is transported and framed; the core request/response semantics remain recognizable across versions.

15

HTTP vs HTTPS

HTTPS adds a protected TLS channel around HTTP communication.

🌐

HTTP

HTTP is the Web application-layer protocol. Without TLS protection, the network path does not provide the same cryptographic protections as HTTPS.

HTTP communication

No TLS protection by itself

Common scheme: http://

VS

🔐

HTTPS

HTTPS uses HTTP over a secure TLS-protected connection.

✔ Confidentiality

✔ Integrity

✔ Server authentication through certificates

Common scheme: https://

16

What Is TLS?

TLS provides the security layer used by HTTPS.

TLS stands for Transport Layer Security.

TLS is designed to provide a secure communication channel between endpoints. Its security goals include authentication, confidentiality and integrity.

01

HTTP Web application-layer communication

↓

02

TLS Secure communication channel

↓

03

Network Transport Underlying transport depends on HTTP version and deployment

17

What Security Does HTTPS Provide?

Understand the three important security goals.

🔒

Confidentiality

Helps prevent network observers from reading protected application data.

PRIVACY

🛡️

Integrity

Helps detect unauthorized modification of protected data.

PROTECTION

✅

Authentication

TLS certificate verification helps the client authenticate the server identity.

IDENTITY

Remember: HTTPS does not mean that a website itself is trustworthy. It protects the communication channel; application security is a separate concern.

18

Digital Certificates

Certificates help clients verify the identity associated with a secure endpoint.

01

Website Identity

The certificate contains identity-related information for the server and is digitally signed by a certificate authority.

02

Certificate Authority

A trusted certificate authority can issue or sign certificates according to the public-key infrastructure.

03

Browser Validation

The browser validates the certificate chain and relevant identity information according to its trust model.

04

Secure Session

After the TLS handshake establishes the required cryptographic parameters, protected application data can be exchanged.

19

Premium Visualizer — HTTPS Connection

Step through a simplified HTTPS connection lifecycle.

🌐

STEP 01

Browser Requests HTTPS

The browser begins a secure connection to the target host.

https://codebhavya.com

What the visualizer teaches

01

HTTPS uses TLS to establish a protected communication channel.

02

Certificates help authenticate the server identity.

03

HTTP application data is exchanged through the protected connection after the security setup succeeds.

20

Premium Simulator — HTTP Request / Response

Select an HTTP method and inspect the corresponding simplified request and response.

SELECT METHOD

REQUEST

GET /api/students/101 HTTP/1.1
Host: codebhavya.com
Accept: application/json

RESPONSE

HTTP/1.1 200 OK
Content-Type: application/json

{
  "studentId": 101
}

21

Caching Basics

HTTP also defines mechanisms that allow responses to be reused efficiently.

A cache can store an earlier response and reuse it for a later equivalent request when the response is permitted to be cached.

HTTP caching can reduce response time and network usage. Headers such as Cache-Control and validators such as ETag are important parts of practical caching.

01

Browser May use cached responses

↓

02

Intermediate Cache May reuse an eligible response

↓

03

Origin Server Generates or returns the representation

22

Real-World Example — Student Result API

See how HTTP concepts combine in an actual application.

Student Result Request

A browser or frontend application wants the result of student ID 101.

It may send:

GET /api/results/101 HTTP/1.1

The application server processes the request and returns a response containing structured data.

👨‍🎓 Student

↓

🌐 Browser

↓

📤 GET /api/results/101

↓

⚙️ Application Server

↓

🗄️ Database

↓

TLS is Transport Layer Security. It establishes a secure communication channel designed to provide properties including authentication, confidentiality and integrity.

Click again to return to the question.

25

Practice Problems

Test yourself without looking back at the lesson.

01

Break the URL https://example.com/products?id=25#reviews into its major components.

02

Explain the difference between GET, POST, PUT, PATCH and DELETE.

03

Explain all five HTTP status-code classes.

04

Explain the difference between an HTTP header and HTTP body.

05

Explain why HTTPS is more than simply putting an "S" at the end of HTTP.

06

Explain what happens when a browser receives an HTTP 404 response.

26

Quick MCQs

Check your understanding.

MCQ 01 EASY

Which part of a URL commonly identifies query parameters?

MCQ 02 EASY

Which HTTP method is defined as requesting a representation of a resource?

MCQ 03 MODERATE

Which status-code class represents client errors?

Digital Certificate

Click to see meaning

DEFINITION

Digital Certificate

A signed digital document used in public-key infrastructure to bind identity information to a public key.

28

Quick Revision

Remember these relationships.

🔗 URL

Resource locator

🌐 HTTP

Web communication

📤 Request

Client message

📥 Response

Server message

🔢 Status Code

Request outcome

🏷️ Header

Message metadata

🔐 HTTPS

HTTP over TLS

🛡️ TLS

Secure channel

🎯

Key Takeaway

URLs identify web resources. HTTP defines how clients and servers exchange requests and responses. Methods describe intended operations, headers carry metadata, and status codes communicate the result.

HTTPS combines HTTP with TLS protection so that the communication channel can provide confidentiality, integrity and server authentication.

These concepts will become the foundation for forms, APIs, AJAX, Fetch, authentication, security and server-side technologies later in this course.