Web API Interview Questions & Answers

Web API Interview Questions: Web API (Application Programming Interface) is a popular framework for building web-based applications that enable different software systems to communicate with each other. Web APIs use HTTP protocols to enable applications to interact with web servers and retrieve data in JSON, XML, or other formats. As web API development has become an essential skill in modern software engineering, candidates must understand the underlying concepts and principles.

Web API interview questions can vary depending on the position and level of the candidate. The interviewer may ask basic questions about HTTP methods, status codes, headers, or more advanced topics like RESTful web services, authentication, security, API design, and performance optimization.

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Interview Questions On Web API

Some common web API interview questions include:

  • What is a RESTful web service, and how does it differ from other web services?
  • What are the advantages of using JSON over other data formats like XML?
  • What is the difference between PUT and POST HTTP methods?
  • What is Cross-Origin Resource Sharing (CORS), and how does it work?
  • How do you secure a Web API?
  • What is an API Gateway, and what is its role in a microservices architecture?
  • How do you handle errors and exceptions in a Web API?
  • What are the best practices for designing a Web API?
  • What is the difference between SOAP and RESTful web services?
  • How do you optimize the performance of a Web API?
  • What is API testing, and how does API testing differ from other types of testing, such as UI testing?
  • What are the key components of an API that need to be tested?
  • What are the different types of testing that fall under the umbrella of API testing?
  • Can you explain the steps involved in testing an API comprehensively?
  • What are the most commonly used HTTP methods in API testing, and what are their purposes?
  • Explain the difference between GET and POST methods in API testing, including when to use each one.
  • How would you test an API that uses the PUT method to update resource data? What considerations are important?
  • Discuss the DELETE method in API testing. How do you ensure that resources are properly deleted without errors?
  • What is the significance of query parameters in API testing, and how do they affect the API request and response?
  • Can you explain the concept of request payload in API testing, and how would you send a JSON payload in a POST request?
  • How do you validate the structure and data types of JSON responses during API testing?
  • In API automation testing, how do you manage test data and environment configurations to ensure consistent testing outcomes?
  • What is the purpose of using assertions in API testing?
  • How do you handle authentication and authorization in API testing?
  • When handling authentication tokens in API requests, what methods or headers would you use to include them in your requests?
  • What is the significance of status codes in API responses? Can you provide examples of the most commonly used HTTP status codes?
  • How do you handle dynamic data in API responses during testing?
  • What is the role of mock servers in API testing, and why are they useful?
  • How do you validate JSON responses in API testing?
  • How do you ensure the security of APIs during testing?
  • Can you discuss the differences between REST and SOAP APIs?

Web API Interview Questions And Answers

What is an API?

The full form of API is Application Programming Interface. We are using APIs as an interface that can help communicate and exchange data between two systems. The APIs are nothing but a collection of functions that are executable by other software application functions. And it also takes the request from a user, processes that request and sends back the response without exposing the internal application details.

What is API testing?

During the API testing, we validate the API meets its expectations in terms of functionality, reliability, performance, and security of the application. We can perform API testing in any software system where we have used multiple APIs. In those APIs, we should focus more on the Business logic layer of the software architecture.

What are the various API Testing Types?

This is a combination of various testing types like:

  • Unit testing
  • Functional testing
  • Load testing
  • Runtime/ Error Detection
  • Security testing
  • UI testing
  • Interoperability and WS Compliance testing
  • Penetration testing
  • Fuzz testing

What are the common tests performed on API?

You can do the following tests on API’s

  • Check is the API is return the expected data or not return anything.
  • Check you are getting the expected data based on your inputted condition data
  • Check is the API is updating any data structure.
  • Check is the API triggers any events or calls of another API.

What are the common Protocols are used in API testing?

There are different protocols are available but in API testing we are mainly used the below protocols:

  • HTTP
  • REST
  • SOAP
  • JMS
  • UDDI

What tools are used for API testing?

Currently, in the market there are somany different API testing tools are available on the internet. Out of all those API testing tools, there are a few which are mostly used and those are Katalon studio, Postman, SoapUi, Parasoft SOAtest, Apigee, JMeter, Apigee, API fortress, JUnit, etc.

What is an API environment?

The API environment is an application programming interface that allows developers to connect the application with the server and database as per the requirement of the software application.

In API testing there is no involvement of the GUI. For this reason, once the installation process is completed we are triggering so many API calls to the original environment and checking the results.

What is an API framework?

The APIs are allowing you to interact with another operating system or application. Based on your request the APIs are tries to pull some of the source code from the framework, which will work with other sources of code or applications of the code. In this manner, the completed information pulled communicated through the API.

Why do we need web APIs?

Web APIs can be used to create RESTful web services using the .NET Framework. They help developers create HTTP services that can be accessed by browsers, devices, or tablets. ASP.NET Web API can be used with MVC to develop any type of application.

What are the advantages of using web APIs?

If you’re looking for a simple, lightweight solution, WEB API is the way to go. It’s fast and can use any text format, including XML. Plus, you can use WEB API to create full-blown REST Services. There’s no need for data contracts or complex configurations like there is with WCF.

What are the different return types in Web API?

The Web API action method can have the following return types.

  • Void – This will return you empty content.
  • Primitive Type/Complex Type – You can write the serialized return value into the response body
  • HttpResponseMessage – This will convert the response to an HttpResponseMessage.
  • IHttpActionResult – this will call internally ExecuteAsync for creating HttpResponseMessage.

Which protocols are supported in Web API?

Web APIs are a way to access different services and data using the HTTP protocol. This makes them easy to use for applications and websites.


Overall, having a solid understanding of web API principles and concepts is a valuable asset for any developer or software engineer. Being well-prepared for web API interview questions can help candidates demonstrate their expertise and succeed in their careers.

If you have any suggestions or questions regarding web API interview questions, feel free to ask them in the comment section below because we value your input and appreciate any feedback you may have. Our goal is to provide accurate and useful information to help you prepare for your upcoming web API interview. So, don’t hesitate to ask questions or share your thoughts; we’ll do our best to provide you with a prompt and helpful response.

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