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Web Services and an Application Programming Interface(API) provide web communication functionality. Though they provide similar functionalities they are not the same. Many channels sometimes use the Webservice and API interchangeably but they are different. They exist to solve different challenges. In Short, API allows the application to communicate while web service allows the system to communicate with each other. The difference between web services vs API can help to understand each of them clearly.



<div id="toc_container" class="no_bullets">Table Of Contents<ul class="toc_list"><li><a href="#Web_Service_vs_API_Overview">1 Web Service vs API – Overview</a><ul><li><a href="#What_is_an_API">1.1 What is an API?</a></li><li><a href="#What_is_a_Web_Service">1.2 What is a Web Service?</a></li></ul></li><li><a href="#Web_Service_vs_API_Examples">2 Web Service vs API – Examples</a></li><li><a href="#Differences_Between_Web_Services_and_API">3 Differences Between Web Services and API</a></li><li><a href="#Web_Service_vs_API_Whats_Right_for_Me">4 Web Service vs API – What’s Right for Me?</a></li><li><a href="#How_to_Do_API_Test_Automation_with_Testsigma">5 How to Do API Test Automation with Testsigma?</a></li><li><a href="#Summary">6 Summary</a></li><li><a href="#Frequently_Asked_Questions">7 Frequently Asked Questions</a><ul><li><a href="#Is_web_service_and_REST_API_the_same">7.1 Is web service and REST API the same?</a></li><li><a href="#What_is_an_example_of_a_web_service_and_API">7.2 What is an example of a web service and API?</a></li></ul></li></ul></div>
<h2 id="web-service-vs-api-overview">Web Service vs API – Overview</h2>



<h3 id="h-what-is-an-api">What is an API?</h3>



An application programming interface (API) is a set of rules that define how applications can communicate with each other. There are different <a href="https://testsigma.com/blog/different-types-of-apis-and-protocols-2022-updated/" target="_blank" rel="noreferrer noopener">types of APIs</a> like GraphQL, REST, WebSocket APIs, RPC APIs, etc. All APIs have their own set of protocols and definitions. So each API type operates differently. 



API is simple to implement and will have a lightweight architecture. It is often assumed that APIs are web APIs, that is information is exchanged over the internet. However, APIs can also be exposed using local files such as JAR without the internet. Web APIs are the most common and widely used.



Components of API



APIs are very lightweight, it involves three main components.



<ul><li>Client: A client can be any external or internal application that makes the request.</li><li>Server: A server executes the program and sends the response.</li><li>API contracts: Request response formats are also known as API contracts.</li></ul>



Read here &#8211; <a href="https://testsigma.com/blog/api-examples/" target="_blank" rel="noreferrer noopener">API Examples</a>



<h3 id="h-what-is-a-web-service">What is a Web Service?</h3>



Web service is a software system designed to support interoperable machine-to-machine communication over the Internet. Web services are designed to provide a specific set of services. Developers can utilize multiple web services to build a single functionality which helps in code reusability and reduces the time and cost of development.



Webservices require a network to interact and network communication is generally achieved using Simple Object Access Protocol (SOAP). SOAP uses XML format for encoding data. The XML format is used for storing and transferring information using HTTP protocol. 



An application sends the requests to a service in XML format. Services then see and process the request and reply to the application as response using the same XML format. Web services can follow <a href="https://testsigma.com/blog/api-rest-vs-soap/" target="_blank" rel="noreferrer noopener">SOAP or REST</a> principles for implementation. However, SOAP is the most widely used.



Types of Webservices



Web Services can be broadly classified into two different types as given below



<ul><li>SOAP Web Service: SOAP is a legacy protocol. Designed before REST.  SOAP became popular as it provides an efficient and secure way to exchange data independent of the software platform.</li><li>REST Web Services: REST is more helpful when your application requires manipulation or exchange of media files, objects, or objects on a hardware device. The service needs to fully adhere to <a href="https://www.knowledgehut.com/blog/programming/rest-api">REST principles</a> to claim the service as a RESTful service. The HTTP verbs such as GET, POST, PUT, and DELETE are used as commands for information exchange.</li></ul>





<h2 id="web-service-vs-api-examples">Web Service vs API – Examples</h2>



APIs are often used to integrate data and functionality from one software application into another. 



For example, a weather app might use the OpenWeatherMap API to retrieve weather data, or a social media app might use the X (Twitter) API to allow users to post tweets.



Web services often provide complete user interfaces for interacting with data and functionality. 



For example, Google Maps is a web service that provides users with a map interface for searching for locations and directions.



It is important to note that some web services also provide APIs. For example, the Google Maps web service also provides an API that developers can use to integrate Google Maps functionality into their applications.



Here are some examples we use in our day-to-day life.



Examples of APIs



<ul><li>Google Search API: This API allows you to blend Google Search functionality into their applications.</li><li>X(Twitter) API: This API allows access and interaction with X(Twitter) data.</li><li>Facebook API: This API allows access to and interact with Facebook data.</li><li>PayPal API: This API allows the integration of PayPal payment processing into their applications.</li><li>OpenWeatherMap API: This API allows you to access weather data from all over the world.</li></ul>



Examples of Web Services



<ul><li>Google Maps: This web service allows users to view and interact with maps of the world.</li><li>Amazon Web Services: This web service provides a wide range of cloud computing services, including storage, computing, and networking.</li><li>PayPal: This web service allows users to send and receive money online.</li><li>Netflix: This web service lets users stream movies and TV shows online.</li><li>Spotify: This web service allows users to stream music online.</li></ul>



<h2 id="differences-between-web-services-and-api">Differences Between Web Services and API</h2>



This is a detailed table that will give you the differences:



<figure class="wp-block-table"><table><tbody><tr><td>Feature</td><td>Web Service</td><td>API</td></tr><tr><td>Type</td><td>A specialized type of API</td><td>A broader interface for communication</td></tr><tr><td>Network Access</td><td>Must be accessed through the network</td><td>May or may not be accessed through the network</td></tr><tr><td>Communication Protocol</td><td>REST, SOAP, XML-RPC</td><td>Various protocols (e.g., HTTP, REST, SOAP, gRPC)</td></tr><tr><td>Data Exchange Format</td><td>XML</td><td>XML, JSON, or custom formats</td></tr><tr><td>HTTP Protocol</td><td>Supports HTTP</td><td>Supports HTTP and HTTPS with headers</td></tr><tr><td>Communication</td><td>Allows machines to communicate</td><td>Allows applications to communicate</td></tr><tr><td>Implementation Approach</td><td>Complicated and legacy</td><td>Simple and modern</td></tr><tr><td>Features</td><td>Document exchange, synchronous/asynchronous operations, RPC, loose coupling, modular design.</td><td>Simple, flexible, secure, language-independent.</td></tr><tr><td>Advantages</td><td>Easy to use, high code reusability, communication and data exchange, speed, agile compatibility, flexibility, security, platform independence.</td><td>Improved connectivity, CRUD operations, HTTP verb support, data exposure, GUI integration, customization, authentication/authorization, multiple formats.</td></tr><tr><td>Disadvantages</td><td>Cannot be accessed directly from browser, requires skilled resources, limited to legacy technologies, security depends on implementation, unreliable HTTP protocol.</td><td>Requires programming expertise, high maintenance cost, fixed scale, infrastructure cost for scalability.</td></tr></tbody></table></figure>



<h2 id="web-service-vs-api-what-s-right-for-me">Web Service vs API – What’s Right for Me?</h2>



Web services are typically accessed through a web browser and often provide a complete user interface for data interaction. Web services are often used to build web applications and mobile apps. Know more &#8211; <a href="https://testsigma.com/automated-web-application-testing" target="_blank" rel="noreferrer noopener">Automated Web application Testing</a>



APIs are accessed through code, providing a programmatic interface for data interaction. APIs are often used to integrate data with other software applications.



Here is a table that recaps web service vs API key differences:



<figure class="wp-block-table"><table><tbody><tr><td>Feature</td><td>Web service</td><td>API</td></tr><tr><td>Access method</td><td>Web browser or client application</td><td>Code</td></tr><tr><td>User interface</td><td>Yes</td><td>No</td></tr><tr><td>Use cases</td><td>Building web applications, mobile apps, and other user interfaces</td><td>Integrating data with other software applications</td></tr></tbody></table></figure>



Which one is right for you?



A web service is an excellent option to access and use data through a user interface. An API is a good option if you need to access and use data through code.



Here are some specific scenarios where you might choose a web service or API:



<ul><li>Web service: </li></ul>



<ol><li>You are building a web application that needs to display data from a remote server.</li></ol>



<ul><li>API: </li></ul>



<ol><li>You are building a mobile app that needs to access data from a remote server.</li><li> You are building a software application that needs to integrate with a third-party service.</li></ol>



Both web services and APIs are helpful tools for accessing and using data. The best choice for you will depend on your specific needs. Consulting with a software engineer or IT professional is always a good idea if you are still deciding which one to choose.



<h2 id="how-to-do-api-test-automation-with-testsigma">How to Do API Test Automation with Testsigma?</h2>



As many organizations are following API-driven development, it is important to test the API. API testing is not as easy as we think. <a href="https://testsigma.com/guides/api-testing/">API testing</a> requires some level of technical expertise as you need to pass the request body, headers, authorization token, etc. Testsigma makes its simpler using the No Code method. Know more &#8211; <a href="https://testsigma.com/automated-api-testing" target="_blank" rel="noreferrer noopener">API Test Automation</a>



Steps to Create API Tests in Test Sigma



Step 1: Log in to TestSigma



Step 2: Click Create Test Case  and Enter the required Details



Step 3: Add RESTFUL API 



<figure class="wp-block-image"></figure>



Step 4: In the REST API window, enter the required details and Click on Create



<figure class="wp-block-image"></figure>



If you are using any tool other than Testsigma, you need to construct the whole request details using the programming languages which includes headers, URL, request body, etc. However in <a href="https://testsigma.com/guides/api-testing/">TestSigma</a> its just a few clicks.









What to Test in API Testing?



API Testing is most critical as it is the middle layer. APIs usually communicate with UI and Database. You can test a lot more in API testing. However, at the minimum, you need to test below key areas.



<ul><li>Response Code</li><li>Response Payload</li><li>Response headers</li><li>API Contracts</li></ul>



Remember, While doing API testing you need to focus on both happy flows, sad/error flows, and edge case scenarios.



It is recommended to perform API testing as much as possible. Compared to UI tests API test are more stable and takes less time to execute. The data and major chunk of application functionality can be tested using <a href="https://testsigma.com/guides/api-testing/">API testing</a>. The web service and APIs are not the same, they exist to solve different problems. The modern web application architecture emphasizes API-driven development. So web APIs are most commonly used across the industry. API also simplifies complex application development and helps in code re-usability and security. API can be implemented in different ways based on needs and other organization-related factors. As the development is aligning with web API the need for API testing is more. Most organizations follow API testing as integration testing as major data-related functionality can be tested within a few minutes. Most of the automation tools support API testing however, setting up an API testing framework takes more time. Importantly, the requirement for skilled resources is a major challenge. Tools like Testsigma make API testing easier and faster. It also comes with DevOps (CI/CD) integration thus it makes developer/tester friendly.



<h2 id="summary">Summary</h2>



In conclusion, web services are a specialized subset of APIs that adhere to specific standards, while APIs offer a more flexible and versatile approach to application integration. Though all web services are APIs, not all APIs are web services: APIs can use any number of protocols and be local or remote.



<h2 id="frequently-asked-questions">Frequently Asked Questions</h2>



<h3 id="is-web-service-and-rest-api-the-same">Is web service and REST API the same?</h3>



Though many of us use the web service and API interchangeably it is not the same. Webservice is the legacy approach used for exchanging data between systems or applications. The REST API is used to interact between two applications.



<h3 id="what-is-an-example-of-a-web-service-and-api">What is an example of a web service and API?</h3>



A payment gateway is an example of a web service. You might have seen login with Google/Facebook etc. while you sign up when you choose Internally it uses the respective organization APIs for authentication.

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