What is API? What is Web Service? REST API & RESTful Web Services 🚀

By Bhau Automation • API Testing & Web Services Tutorial

🎯 What You Will Learn

What is API?
What is Web Service?
Difference between API and Web Service
REST API Introduction
RESTful Web Services
API Automation Testing Basics
REST API Interview Questions

💡 API Testing and REST API concepts are among the most frequently asked topics in Software Testing, Selenium, REST Assured and Automation Testing interviews.

📌 What is an API?

API (Application Programming Interface) is a communication bridge that allows two software applications to exchange information and interact with each other.

Real-world API examples:

Google Maps API
Paytm Payment API
Facebook Login API
Weather API
Instagram API

🌐 What is a Web Service?

A Web Service is a type of API that uses web protocols like HTTP and HTTPS to communicate over the internet.

Important Rule:

All Web Services are APIs
Not all APIs are Web Services

⚡ Difference Between API and Web Service

Feature	API	Web Service
Communication	Direct or Network	Network Based
Protocol	Any Protocol	HTTP/HTTPS
Internet Required	Not Always	Yes

🚀 What is REST API?

REST API (Representational State Transfer) is a lightweight architecture used for communication between client and server applications.

REST APIs commonly use:

GET
POST
PUT
DELETE
PATCH

REST API Example

GET /users

POST /users

PUT /users/101

DELETE /users/101

📦 What is RESTful Web Service?

A RESTful Web Service follows REST architecture principles and uses HTTP methods to perform operations on resources.

Stateless Communication
Client-Server Architecture
Resource-Based URLs
JSON Data Exchange

💻 Sample REST API Response

{
   "id":101,
   "name":"Bhau Automation",
   "role":"Tester"
}

🎯 API Automation Testing

API Automation Testing validates:

Status Codes
Response Time
Response Body
Headers
Authentication
Business Logic

🔥 Why REST APIs Are Popular?

Fast Performance
Lightweight JSON Format
Easy Integration
Scalable Architecture
Cloud Friendly

🌍 Real-World Applications

E-Commerce Websites
Mobile Applications
Banking Systems
Payment Gateways
Social Media Platforms
Automation Testing Frameworks

❓ Frequently Asked Interview Questions

Q: What is API?

A: API is a mechanism that allows applications to communicate with each other.

Q: What is REST API?

A: REST API is an architectural style that uses HTTP methods for communication.

Q: What is the difference between API and Web Service?

A: All Web Services are APIs, but not all APIs are Web Services.

🎥 Watch Complete Video Tutorial

👉 Watch REST API & Web Services Tutorial

🎓 Key Takeaways

API enables software communication
Web Service is a type of API
REST APIs are lightweight and fast
RESTful Web Services use HTTP methods
Important topic for API Testing interviews

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What is API and Web Service? REST API Introduction & RESTful Web Services Complete Guide