What is the Best API Automation Testing Tool?

Best API testing tools

10+ Best API testing tools

This post will summarize the best API testing tools comprising commercial and open-source solutions. API is an acronym for Application Programming Interface. API is a set of tools, protocols, and routines for building software applications. APIs define how software solutions should interact with other software.  API testing is application testing that concentrates on testing APIs directly. It also entails integration to verify if the API meets exceptions concerning the application’s reliability, security, performance, and functionality. The main focus of API testing will be on the software architecture’s business logic layer. 

Google Trends reports that the interest in API testing has been increasing steadily. Having the proper process tool and solution for API automation tests is becoming more vital than ever. API tests are a critical component of a successful CI/CD deployment with the shift-justify trend. 

Table of contents:

  1. API definition
  2. What is API testing?
  3. Why use an API testing tool?
  4. The best test automation tools
  5. Frequently asked questions(faq)

API Definition

API Definition

Application programming interfaces (APIs) allow applications to communicate and interact with each other by establishing precise determinations and rules. Specifically, they are accountable for stipulating the type of request that software can make to another and defining the following three aspects: what practices the user must follow, how to make API requests, and what data format. Thanks to APIs, software connected to the internet can send the request (with data) to a server, and, in turn, the server will retrieve the request and interpret it. When the necessary actions are executed, it responds to the software’s user interface with information. 

What is API Testing?

API testing comprises software that tests how the APIs were established. It analyzes if the APIs correctly fulfill their purpose to ensure the application’s performance, security, reliability, and functionality are not compromised. Additionally, API testing mainly consists of testing SOAP web services or REST APIs and deploying JSON or XML message payloads sent via JMS, MQ, HTTP, and HTTPS. 

API testing tools enable testers to verify many aspects, including:

  • The time it takes to deliver a response
  • If it responds securely to possible security attacks
  • If it reacts adequately to edge cases (such as unexpected inputs and failures)
  • If an API is returning the expected response and in the right format

Why use an API Testing Tool?

Since all the software application components are mostly loosely coupled, it is crucial to test the APIs. APIs reside in the business layer, which is likely to change many times. Through automated API testing tools, you can detect any format changes in request/response, or if there are any changes to the API itself, early in the testing phase. This simplifies the regression and integration testing phases, contributing to a shorter software testing life cycle.

API testing tools perform load testing, rest API testing, functional testing, security testing, reusability, and load testing. Which API automation tool should you choose? Keep reading to see our favorite picks!   

The Best Test Automation Tools

SoapUI Logo


SoapUI is a functional testing tool fully dedicated to API testing that allows executing tests on SOAP APIs and web services REST, considering that it is headless. It is usually one of the preferred tools by developers and testers since it enables them to create sophisticated scenarios and further supports asynchronous testing. Besides, it also stands out for its significant data-driven testing and ease of use. One of the critical features of SoapUI is the reusability of scripts- load tests, and security scans can be reused for functional test cases in just a few steps.Additionally users can drag-and-drop elements to build out their tests.

SoapUI provides two packages, one free and the other paid (the pro package). The free software is fairly easy to use, and testers can reuse scripts. The pro package can also extract data (from files, excels, and databases), create custom codes, and support CI/CD integrations.

Pricing: Using the free package of SOAPUI, users can get the full source code and build their preferred features.  

Apigee Logo


Apigee is an interesting cross-cloud API testing tool powered by JavaScript that enables developers and testers to access its features through different editors.

This API testing tool is compatible with APIs that comprise significant amounts of data, being ideal for robust and sophisticated digital businesses. Besides, it can quickly identify problems compromising performance by analyzing the API traffic, potential error rates, and response times. In addition, Apigee also allows the creation of proxies from Open API Specifications. Afterward, businesses and testers must select the most suitable package to continue deploying. The existing packages are evaluation, enterprise plus, and standard enterprise.

Tricentis Tosca Logo

Tricentis Tosca

Tricentis Tosca is a robust web services testing tool. Key API testing features of Tricentis Tosca are:-

  • It integrates into DevOps Cycle and Agile.
  • This web services test tool supports various protocols, including NET TCP, IBM MQ, REST, SOAP, TIBCO EMS, and RabbitMQ. AMQP, HTTP (s) JMS.
  • Allows end-to-end testing as API tests can be utilized across mobile, packaged apps and cross-browser, etc.
  • Tricentis Toscas is one of the most popular API automation tools which utilizes model-based test automation that makes script maintenance simple.
  • Interactive testing offers test managers the ability to execute manual testing and gather results without having to configure Tosca environments.  

Hippie Swagger Logo

Hippie Swagger

Hippie-swagger is an automation tool for testing APIS. It is one of the top API testing tools which supports a clear assertion syntax for extending test behavior. It also enables clean printing reports.

Key features of Hippie Swagger

  • Validated parameters, pats, response, request, etc
  • Readable and accurate assertion messages
  • It will fail the test whenever swagger documentation is either missing or erroneous

ReadyAPI Logo


ReadyAPI pricing: The pricing options accessible with ReadyAPI are SoapUI (which begins at $659 annually), ServiceV Pro (which starts at $1199 annually), and LoadUI Pro (which starts at $5999 per year), and ReadyAPI (Custom pricing). Users can try the Ready API for fourteen for free.  SmartBear offers the ReadyAPI platform for the security, functional, and load testing of GraphQL, SOAP, RESTful SOAP, and other web services.

In one intuitive platform, users can get four powerful fools., API performance testing, API functional testing, API and web virtualization, and API security testing. This platform will assist you in ensuring end-to-end for all web services.  It offers flexible automation options for integrating API testing into your CI/CD pipeline during each build. You will be able to create extensive and data-driven functional API tests. 

Key features for ReadyAPI

  • It also supports Command-line for automated testing
  • It provides native support for Azure, Jenkins, Docker, and Git
  • It has a Smart Assertion functionality that can create bulk assertions against numerous endpoints rapidly
  • ReadyAPI can be integrated into any environment
  • ReadyAPI also offers features for removing dependencies during development and testing
  • It also provides functionalities and features for reusing the functional tests and generating realistic load scenarios
  • It supports job queuing and parallel execution of functional tests

ReadyAPI works best for DevOps and Agile Teams. It is the best automation tool for the security, functional, and load testing of RESTful, GraphQL, SOAP, and other web services. 

Rest-assured Logo


REST-assured is regarded as one of the best tools for testing APIs in Java. It is an open-source platform with a Java Domain-specific language. The Rest-assured API was developed so that you do not need to be an expert in HTTP to test web APIs.

Pros of Rest-assured

  • It supports the syntax of Behavior Driven Development (BDD) testing- Given, When, Then.
  • You do not have to code things from scratch as it comes with some inbuilt functions.
  • You do not have to be an HTTP expert.
  • Enables testing Rest services more simply
  • Rest assured integrates seamlessly with the Serenity automation framework so that users can combine the REST and UI tests all in one testing framework that generates awesome reports.

Cons of Rest-assured

  • Rest-assured does not support APIs explicitly
  • It supports only the Java language

Karate DSL Logo

Karate DSL

Karate DSL is a unified tool for API automation testing, load testing, performance testing, and mocks. Test scenarios for API-based BDD tests have never been simple to develop. 

On the other hand, Karate has all the step definitions written for developers, so we do not have to be concerned about writing them. Developed by Intuit, this automation tool is specifically developed for automated API testing. The karate platform is based on the cucumber library. With this automation tool, a tester can test web services by writing tests in a domain-specific language. Business users do not need to possess programming skills to use this tool. 

However, having some basic knowledge of XPath, JSON, HTTP, and JSONPath is an asset.

Top features highlights  

  • Programming skills are not needed to use this tool
  • Business users can reuse payload data and user-defined functions across tests with this automation tool
  • Generating and testing reports are supported in the same way as other Java projects
  • There is support for configuration switching and parallel multithreading execution
  • Provides powerful assertion capabilities
  • API tests can be written in almost any language that deals with XML, JSON, or HTTP

Airborne Logo


Airborne is an open-source API testing automation framework. It is a Ruby-based RSpec-driven framework. This tool does not have a UI. It just provides the text file to write the code.

Key features highlight

  • It can work with Rack applications.
  • Airborne can work with APIs which are written in Rails.
  • To deploy this tool, you must know Ruby and RSpec fundamentals.

Postman Logo


Even though it was built as a plugin for Google Chrome, Postman can also be deployed with Mac and Windows and is an excellent tool for testing API services, including running http requests, debugging, monitorization, etc.

Postman does not require testers and developers to learn a new language and further supports various formats (like RAML and Swagger). Additionally, it also provides built-in tools, collections, and workspaces. Contrary to CURL, Postman is not a software tool based on the command line; developers and testers do not need to paste the text into the command line window.  Postman is a free API testing tool. Users who wish to benefit from additional features cost $12 per month per user. 

Assertible Logo


Testers and developers widely perceive Assertible as one of the best API automation testing tools with a high focus on reliability, considering it supports API tests at every step that goes from continuous integration to the delivery pipeline. Besides, Assertible offers users very beneficial features. It supports integration with Slack, Zapier, and GitHub. Moreover, Assertible also validates HTTP responses with turnkey assertions.

This API testing tool provides three different packages. The standard version costs $ 25 per month; the startup tier is $50 monthly; the business tier is the most costly package (and the one that provides more features), which costs $100 per month. Additionally, a free personal plan is ideal for executing more manageable API tests and understanding how Assertible works. 

Ping API Logo

Ping API

Ping API is an API testing tool that allows users to write test scripts in JavaScript and CoffeeScript to test their APIs. Ping API is one of the best API testing tools which enables inspecting HTTP API calls with complete request and response data. The user gets a notification via Hipchat, Slack, or email for any failures.

Features of Ping API

  • Ping-API is one of the top API tools that validate CRUD flow and log in to Ping API.
  • Support writing scripts to set request headers, URL, and body parameters. It supports writing scripts to validate response headers and body.
  • Ping-API to schedule tests every minute or hour

Katalon Studio Logo

Katalon Studio

Katalon Studio tool brings a hassle-free API testing platform for testers with or without programming experience. 

Top key features highlights

  • Support set up API test data deploying UI testing
  • Support automated and exploratory testing
  • Users can create fluent assertions in BDD style with AssertJ support
  • Built off of data-driven testing methods, better API test coverage
  • Easily import tests from WADL, WSDL, Postman, and Swagger
  • Supports all kinds of SOAP, REST requests, SSL client certificate
  • Support AssertJ, one of the best assertion libraries, to develop fluent assertion with BDD style
  • All-in-one shop fr WebUI, desktop App, API, mobile applications, and the combined capabilities.

TestGrid Logo


You can think of TestGrid API testing as a lightweight, web-based API development suite with a minimalistic UI design, which is 70-percent faster than the traditional API automation process to assist you in testing faster and releasing better. You engage your software testing teams to build and execute test cases without prerequisites of programming knowledge. 

Top features

  • Integrates with your favorite CI/CD tool for continuous testing
  • Scriptless testing for faster automation
  • Transaction monitoring
  • API integration automated testing
  • Performance testing to assist you in optimizing and improving your API
  • Fetch a detailed report of the number of Source Type, Response Size, Request Size, Speed, Duration, Response Data, and Request Data 
  • Deeper Assertions- can write test cases that validate against API calls and supports MITM
  • Simple to use API automation for SOAP and REST calls

RedwoodHQ Logo


RedwoodHQ is an open-source tool that assists in testing API SOAP/REST and supports multiple languages such asJava/Groovy, Python, and C #. This automation tool supports multi-threaded execution and also enables the user to compare the results from each of the runs.

Eggplant Logo


Eggplant is the leading test automation industry that offers true end-to-end API testing. 

Top features:

  • Easily build API tests with pre-configured snippets, Sense Talk scripts, and parameters
  • Combine API automation testing with validation of the UI to understand real-world performance and behavior
  • Auto-generate test automation assets by analyzing and collecting metadata by hooking into APIs
  • Discover and point out anomalous behavior before your users encounter it
  • Easily add additional guidelines and steps beyond simple API call and response
  • Understand how the API behaves with both invalid and valid values

Parasoft SOAtest

Parasoft SOAtest

Establish a foundation of automated tests that can be executed as part of your DevOps pipelines and continuous integration. Parasoft SOAtest automates the continuous testing of sophisticated systems by creating codeless API test scenarios from manual recordings. SOA test efficiently transforms your test artifacts into performance tests and security tests, reducing redundancy and increasing reusability. 


  • Seamlessly integrated with load testing and service virtualization
  • Keep test assets in sync with evolving systems through automation
  • Leverage artificial intelligence to create powerful test cases in less time than other tools
  • Automatically generate codeless API tests that are reusable, robust, and easily shareable



ACCELQ is a unique test automation platform offering that concentrates on the design and maintenance aspects of the test automation life cycle. You will be pleasantly surprised by its intuitiveness and comprehensiveness when you use it.  It is a cloud-based continuous testing platform that provides a codeless approach to test automation. It provides test management and test automation capabilities for both functional testing and API testing. 

Feature highlights

  • Ensure seamless integration between corresponding APIs and business processes
  • ACCELQ automatically generates test cases deploying artificial intelligence (AI)
  • To guarantee reliable test execution, this tool adapts intelligently to unexpected changes in the application software
  • ACCELQ automates API testing without requiring users to write a single line of code

JMeter Logo


JMeter is an open-source tool. It is developed to do load testing, but it is widely deployed for functional API testing. 

  • JMeter can be used for both static and dynamic resources performance testing
  • It can be integrated with users, and Jenkins can include the API tests in CI pipelines
  • It enables the team to create unique data for API tests via CSV files rapidly
  • It allows the users to replay the test results
  • It has plugins based architecture and can generate test data
  • It will enable you to deploy various programming languages

JMeter has been packed with multiple features and enhancements, improved user experience, and many bug fixes, like new protocol, HTTP Samplers, StringtoFile, JDBC improvements, and JMESPath extractor.

API Fortress Logo

API Fortress

What do you check in an API automation tool from an API testing perspective? It should let you know if the API is up and running, and the second is one of the response times. Generally, API fortress satisfies both requirements and proves to be a good API testing tool. This enables full API testing, including regression tests and like all other tools, comes with functionalities such as reporting, notification, alerts, and SLA monitoring.

HttpMaster Logo

HttpMaster automation tool

HttpMaster platform is a web development tool to automate web applications testing, including service testing, API testing, and website testing. It is one of the top web API testing tools, mainly deployed as a web API test tool to automate the testing of web API calls. 

  • HttpMaster is the best choice for API testing as it has got
  • Various validation types and advanced validation expressions
  • Dynamic parameters of several data types to make batches of different API requests
  • Various HTTP methods (GET, DELETE, POST, etc.)

Frequently Asked Questions(FAQ)

What is an API test?

Application program interface or API is a collection of procedures and functions through which other software applications can be executed or accessed.

Which are the top API testing tools?

In a nutshell, here are the best API testing tools:

Name of tool Platform Best for Price About tool
Katalon studio Linux, macOS, Windows Automated testing It comes with a free license with paid support services An extensive API, Mobile testing tool, and Web Desktop for beginners and experts
ReadyAPI Linux, Mac, Windows Security, functional tests, and load testing of API and web services It begins at $659/year It is the platform for the security, functional, and load testing of RESTful, GraphQL, SOAP, and other web services.
Postman Chrome browser-plugin, chrome, Linux, Mac, and Linux API testing Postman is an API development environment. Pricing: free plan

Postman Pro: $8 for every user per month

Postman Enterprise: $18 for every user per month

ACCELQ Cloud-based continuous testing Automated API testing with automated test design, complete test management, codeless automation logic, 360 trackings, and API regression planning. Codeless API test automation, seamlessly integrated with UI testing A free trial is available.

Pricing begins at $150.00 per month, including DB, UI, API, and Mainframe automation.

What are the advantages of API?

The important advantages of API are:

  1. Content can be embedded from any site or application, or site
  2. Companies can customize the service with ease
  3. It helps you to personalize user experience
  4. Businesses can update the workflow to become more productive

What are the basic general features of API testing tools

The basic features of API testing tools are:

  • It has a simple to use UI
  • Allows you to write tests even for non-programmers
  • Support advanced validation expressions and various validation types
  • Exhaustive features to rapidly validate your REST APIs

What are the different types of software tests?

Functional tests

Functional testing checks a website, application, or system to ensure it is doing exactly what it is supposed to be doing. 

Unit testing

It concentrates on the smallest unit of software design. We test an individual unit or group of interrelated units in this type of testing. The programmer usually does it by deploying sample input and observing its corresponding outputs.

End to end testing

End to end testing is an approach that tests the application’s workflow from beginning to end to ensure everything functions as anticipated.

Regression testing

Every time a new module is included leads to changes in the program. This kind of testing makes sure that the whole element works appropriately even after adding elements to the complete program. 

Acceptance testing

Acceptance tests ensure that the end-user (customers) can attain the goals set in the business requirements, which determines if the software is acceptable for delivery. Acceptance testing is also called user acceptance testing (UAT). 

Integration tests

The aim is to take unit-tested elements and build a program structure that has been dictated by design. Integration testing is testing in which a group of elements is combined to produce the output:

Integration testing is of four types: Big-Bang, Sandwich, Bottom-up, and Top-down.

Load tests

This non-functional software testing process determines how the software application behaves while being accessed by many users simultaneously. 

Security testing

Security testing unveils the system’s vulnerabilities to make sure that the software system and application software are free from any risks or threats. These API tests aim to find any possible flaws and weaknesses in the software system that can lead to a business’s loss of data, reputation, or revenue per employee or outside.

System testing

This software solution is tested to work well for the different operating systems. It is covered under the black box testing approach. In this approach, we focus on the required output and input without concentrating on internal working.  We have performance testing, stress testing, recovery testing, and security testing in system testing.

Is API automation testing in demand? 

APIs are vital to providing customers with an effective and connected experience, and as a result, companies are starting to see their value. API automation testing has become increasingly essential because of the growing complexity of the IT sector and advances in software development technologies. 

Does API automation testing require coding?

Automated testing is highly commended for API testing, especially for DevOps, continuous delivery, and agile development. Automated testing utilizes testing tools that need no coding, but manual testing requires coding to test the API. Generally, automated API testing is preferred for faster and better results than manual API testing.

What is the best API automation testing tool?: Final thoughts

When selecting an API testing tool, it is vital to consider how every different option available in the market might be more suitable for various purposes. Sometimes testing teams and developers may even opt to use more than one tool, considering that it can be sophisticated to find the ideal tool. Thus, development teams should prioritize the “must-have” features they seek.  Thus, even if all the mentioned solutions in this post hold a high-quality reputation, the best API testing tool is the one that better fulfills your business needs. 

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