What Is The Best Tool For API Testing?

Leading API Testing Tools

Leading API Testing Tools on the Market

Application Programming Interface testing (API testing) has become increasingly important as many cloud applications, and related platforms have grown. The bulk of the services we use daily are made up of numerous interconnected APIs, and if one of them fails, the entire service can be jeopardized. Fortunately, application programming interface testing tools on the market may assist us in ensuring that everything runs properly.

Table of content:

  1. What is an API?
  2. What is API Testing?
  3. The 10 API Testing Tools 
  4. How to Pick an API Testing Tool?

What is an API?

APIs (Application Programming Interface) set exact rules and determinations that allow apps to interact and communicate with one another. They are in charge of defining the types of requests that an application can make to another and the three aspects of how to make those requests: how to make them, in what data format, and what practices the user must follow. APIs allow an internet-connected application to send a request (complete with data) to a server, then retrieve and interpret the request. When the required activities are completed, the application’s user interface receives a response containing information.

What is API Testing?

API Testing

API testing is software testing that examines how APIs were created. It examines whether the APIs are performing as intended to guarantee that the application’s functionality, dependability, security, and performance are not jeopardized. Furthermore, API testing primarily comprises putting JSON or XML message payloads across HTTPS, HTTP, MQ, and JMS to test SOAP web services or REST APIs.

API testing tools enable testers to check a variety of factors, including:

  • if an API returns the intended response in the expected format; if it responds appropriately to edge circumstances (such as failures and unexpected inputs);
  • whether it responds to potential security threats securely;
  • The time it takes for a response to be delivered.

The 10 API Testing Tools 

API Testing Tools 

The Best API Testing Tools

Software companies must determine whether the final product meets their expectations. On the other hand, API testing focuses on ensuring that applications meet functionality, performance, reliability, and security requirements. On the other hand, API automation tests are key components of successful testing. Automation solutions are a critical component for increasing your development team’s efficiency (Integrated development environment). Manual testing is a time-consuming and error-prone process that can be avoided using the API test automation tool(s).

Furthermore, an automated API test tool can often be integrated with your continuous integration workflow. This integration is an excellent way to improve the quality of your code by catching defects early in the software development process.  API testing functionality requires the use of the appropriate techniques and tools. The following are ten of the top API testing tools:

  1. Postman
  2. Soap UI
  3. Apigee
  4. Assertible
  5. Karate DSL
  6. Rest Assured
  7.  JMeter
  8. API Fortress
  9. Hoppscotch
  10. Testim

Postman logo


Postman was first released as a Google Chrome extension. Its primary goal was to evaluate API services. Postman’s services are now available for Windows, Mac, Linux, and Chrome browser-plugin. It’s a terrific choice whether you’re searching for exploratory testing or manual testing. Let’s take a look at why. 

Features of Postman

You can use Postman to monitor the API business model, develop automated tests, debug, and run requests. 

 The following are the characteristics of Postman:

  • Its user interface allows users to extract data from web APIs.
  • Postman is a command-line application that allows you to write Boolean tests.
  • Built-in tools, collections, and workspaces are all included.
  • It can read and write in various formats, including RAML and Swagger.

Pricing: Postman is an API testing tool that is available for free. On the other hand, additional features cost $12 per month per user.

Soap UI logo

Soap UI

Soap UI allows you to test REST (REST tests) and SOAP APIs for web services. It’s a headless functional testing tool of two types: free and fixed.

Features of Soap UI

The free package gives users complete access to the source code, whereas the Fixed package allows you to proceed with application programming interface testing. So, let’s compare and contrast the characteristics of the two programs.

SoapUI Free Package

The SoapUI free bundle is the way to go if you’re just getting started with automation or have a limited budget. Its main characteristics are as follows:

  • Due to reusable scripts, it is possible to reuse security scans and load tests for functional test cases.
  • Simple and rapid test creation with point-and-click and drag-and-drop features

SoapUI Fixed Package

Although the Fixed package has a price tag, the following benefits are well worth the money:

  • REST, GraphQL, SOAP, JMS, and JDBC testing
  • Support for asynchronous testing
  • Data-driven testing
  • Synthetic data generation
  • Integrated API security testing

Consequently, an increasing number of digital businesses are choosing the fixed package.

 Pricing: There are no fees included in the free package. The “Fixed” version, on the other hand, starts at €640 a year for users who want to take advantage of its features.

Apigee logo


Apigee is a cross – browser API testing tool. Different editors, such as Swagger, can access the functionalities. API performance can be measured and tested.

Features of Apigee

Apigee is a JavaScript-based multistep utility that includes the following features:

  • Tracks error rates, API traffic, and response times to identify performance concerns.
  • Creates API proxies using the Open API Specification and deploys them in the cloud. 
  • Compatible with APIs that include a lot of data.
  • Apigee is a cross-cloud API testing tool.

Pricing: Apigee provides a free trial for users to test its compatibility with their individual needs. These are the four packages available.

  1. Evaluation
  2. Standard
  3. Enterprise
  4. Enterprise Plus 
Evaluation  Users can test features in their sandbox with evaluation.
Standard  Standard facilitates the execution of an API program.
Enterprise Users can create and scale API apps across the organization with Enterprise.
Enterprise Plus  Enterprise Plus makes running a digital company platform easier, fostering a developer and partner ecosystem.

To inquire about the price of each package, one should contact sales, i.e, a sales team.

Assertible logo


The fundamental objective of Assertible is reliability. It’s a popular choice among new developers, and it has a lot of essential features.

Prominent Features of Assertible

From continuous integration to the delivery pipeline, Assertible facilitates the automation of functional API tests at every step. It also possesses the following advanced features:

  • After an API has been deployed, it is possible to perform tests.
  • Turnkey assertions provide HTTP replies and their validation, i.e., advanced validation expressions. Slack, GitHub, and Zapier are among the tools that can be integrated.

Pricing: The standard plan is $25 per month, the starting plan is $50 per month, and the business plan is $100 per month. If you want to try Assertible for yourself, a free personal plan is available.

Karate DSL logo

Karate DSL

It’s never been easier to create test scenarios for API-based BDD tests. Users can achieve this with Karate DSL without writing down step definitions. It has also built such definitions, allowing customers to start testing APIs as soon as feasible. 

Prominent Features of Karate DSL

WebSocket async capability-based support is included in Karate DSL version 0.9.6. Karate UI has support for multithreaded parallel execution and configuration staging/switching, as well as easy-to-write tests for individuals who aren’t familiar with core programming. Furthermore, because the tool is built on top of the Cucumber-JVM, you may test cases just like any other Java project. Instead of Java, you’ll need to develop scripts in a programming language/ scripting language that makes working with JSON or XML easier.

Pricing: The pricing for Karate DSL is open-source. This implies that the program will be provided free of charge. However, the costs of the solutions will be determined by the requirements.

Rest Assured logo

Rest Assured

Rest Assured is a popular API testing tool that makes testing REST services (services from REST) simple. It’s an open-source Java domain-specific language and open-source tool that makes REST testing easier. Furthermore, issues with OSGi support have been resolved in the newest version. When it comes to employing Apache Johnzon, it also provides additional help. 

Prominent Features of Rest Assured

Rest Assured requires Java 8 or above, starting with version 4.2.0.

The following are the qualities of Rest Assured:

  • Users don’t have to start coding from the beginning because of baked-in functionality.
  • Users don’t need to be familiar with HTTP to use it.
  • REST testing and UI can be combined in a single testing framework.
  • The Serenity automation framework allows for seamless integration.
  • Several authentication schemes are available.

Pricing: Rest Assured’s price is open-source. This suggests that the software is free, but the solutions are not.

JMeter logo


JMeter 5.4, which included bug fixes and core updates, was released in December 2020. JMeter was originally designed for load testing; however, it is now widely used for functional API testing. In addition, the user experience is superior to prior versions. Let’s have a look at JMeter’s preferred features.

Key Features of JMeter

Thanks to the JMeter and Jenkins integration, users can integrate API tests in CI workflows. For performance testing/ performance tests, JMeter works with both static and dynamic resources. JMeter also works with CSV files, allowing testing teams to build custom parameter values for tests.

Pricing: Open-source API testing tool pricing is available for JMeter. The services are paid, but the software is available for free.

API Fortress logo

API Fortress

API Fortress makes performance and functional testing easier to create, execute, and automate. As a result, it’s the most powerful SOAP and REST monitoring tool available. The tool is also well-known for its simplicity. Let’s have a look at some of the other features now.

Prominent Features of API Fortress

API Fortress helps developers avoid redundancies and remove silos from an organization by boosting transparency. Its user interface is ideal for beginners with only little technical knowledge. It also has a one-click test integration feature and is compatible with physical hardware and the cloud.

Pricing: API Fortress costs anything between $1,500 and $5,000 per year. The project’s specific requirements also determine the amount an organization must pay.

Hoppscotch logo


Hoppscotch began as Postwoman, an open-source programming interface testing application that replaces the widely used Postman API tester. After more than a year, the project script has gained over 26.000 stars on GitHub and a new name. The project was built by Liyas Thomas, who first revealed it on Hackernoon.

Prominent Features of Hoppscotch

Hoppscotch bills itself as a simple API testing tool with a clean and rich interface. The API tools come with a comprehensive set of features that make testing a breeze. Here are a few noteworthy features.

  • Over a single TCP connection, establish a full-duplex communication channel.
  • With a SocketIO server, you may send and receive data.
  • An HTTP connection was used to send events from the stream server.
  • MQTT Broker topics can be subscribed to and published.
  • Send GraphQL queries.

 You may access a history of past calls, construct collections for storing API requests, and configure a proxy to access prohibited APIs, just like you do with Postman.

Pricing: Hoppscotch is free to use. However, donations can be made through PayPal or Patreon.

Testim logo


Testim is essentially a full-fledged test automation platform, with API testing as a subset. The unique aspect of Testim is that it employs artificial intelligence to aid in the execution, maintenance, and even generation of test suites. Of course, testing your API functionality is a part of this.

Prominent Features of Testim

The key feature is a framework that learns as each test suite is executed and maintained. You can also construct API actions and validation types for common testing tasks. However, you may isolate your UI testing by collecting data from your API and exercising the user interface efficiently. It’s a great approach to test both the customizable interface and the API simultaneously.

Pricing: Testim operates on a freemium approach, making it simple to get started without spending any money. You can then tailor the pricing to your team’s requirements.

How to Pick an API Testing Tool?

How to choose an API Testing Tool

Many API automation testing tools are available. But how can you choose the ideal tool for your needs? Here are a few things to keep in mind.

  1. The tool’s ability to work with a continuous integration pipeline (CI Pipeline)
  2. Asynchronous tests can be done to reduce test execution time.
  3. The ability to group API requests or organize them into collections, as well as an easy-to-use interface
  4. For teams, quick sharing or synchronization options are available.
  5. API documentation can be generated straight from the Application Programming Interface testing tool.

Relevant Information on the Best Tool for API Testing

More Information on the Best Tool for API Testing

  • DevOps and Agile Teams (agile development teams) benefit from ReadyAPI. It’s the perfect tool for RESTful requests, SOAP, GraphQL, and other web services’ functional, security, and load testing.API functional testing, API performance testing, API security testing, and API & Web virtualization are all available in a single platform.
  • JMeter is a powerful tool for web application load and performance testing.
  • Tricentis Tosca is a model-based API automation testing solution that enables Application Programming Interface testing from Tricentis. 
  • Tricentis is one of the best options for incorporating Agile and DevOps cycles into their workflow. It uses model-based test automation, which makes script maintenance easier and allows for quick regression testing, i.e., regression tests. One of the primary benefits is that it supports various protocols, including REST, SOAP, HTTP(s), MQ, JMS, NET TCP, IBM MQ, etc.
  • WebInject is a tool that creates test cases using an XML API and produces an HTML and XML report with pass/fail status, errors, and response times.
  • Poster (Firefox Extension)- This Add-on allows users to customize their HTTP requests by interacting with online services, and it generates test results that the user can verify.
  • Without writing a single line of code, ACCELQ is the first cloud-based continuous testing tool that effortlessly automates API and web testing.
  • Parasoft, an API Testing tool, assists in creating automated test cases that can be reused and readily maintained, reducing the amount of time spent on regression tests. It offers a very user-friendly UI and supports end-to-end testing.
  • CI/CD integration is supported by katalon studio.
  • Apigee’s API Business model includes IP whitelisting, Java & Python-Based REST API testing platform callouts, and distributed traffic management.
  • Soap UI offers two packages, one of which is free and the other of which is charged (the pro package). The free solution is simple to use, and testers can reuse scripts. It can also write custom code, extract data (from databases, files, and excels), and support native CI/CD integrations with the pro package.
  • Ping API: Ping API is an API monitoring and testing solution that is fully automated. It is very simple to use. It allows the user to write a data-driven test case using JavaScript or Coffee Script, execute tests, and schedule tests, i.e., powerful data-driven testing. Any errors are communicated to the user via email, Slack, and Hipchat.
  • SOAP Sonar is a service and API testing tool developed by Crosscheck Network, a significant API tool developer.
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