Top 17 Best API Testing Tools for Developers [For More Accurate Testing]

APIs or Application Programming Interface(s) are automated means to integrate with applications’ or website’s backend to carry out more features and extra functionality to the software. Their emergence has changed the programming long-form myths from head-to-toe, as they are tiny packets of actionable code which can be integrated following their easy documentation. Hence, reduce the need for heavy coding.

For all types of API, testing is a must to check out their functionality, authenticity, responsiveness, and reliability before integrating it for final impact.

So, if you haven’t tried API testing tools or know how many types of API testing tools there are, don’t dig further. We’re taking you to in-depth learning of the API analysis route, the available top API testing tools, their compatibility, features, and market trends, so you can better make your online performance only of its kind.

After reading this article, you’re all set to buy the perfect API testing tool for eliminating each doubt from the developmental end. SO, let’s get straight into the details.

What Is Api Testing?

API testing can also be stated as software testing in which APIs integrated go through a series of functional examinations, where each segment of API is analyzed. During the testing process, APIs can be directly observed (overall) or can be examined as a part of software, to let developers understand whether this API performs its specified job accurately or not.

In a business website or application, there are three layers (data, service, presentation), in which the middle layer holds API and allows testing procedures to negotiate this layer using appropriate tools. Since API enables one application to get connected with others, it makes an application’s service or function through elaborating the business goal to achieve. For instance, APIs specific for finance applications, enable users to get financial data, and further lead them to successfully meet decision-making processes.

In short, if services are not attractive or features supporting this layer are not defined even by integrating API, the testing team will have extra negotiation required to access expected results.

Why Do You Need an API Testing Tool?

API testing in applications is as important as qualifying a student to become a teacher in the future. Without testing the eligible student’s skills, abilities, passion, and concerns of becoming a dedicated teacher, he/she will never be approved or allowed to hold the main responsibility. Similarly, letting applications perform their tasks in the market where users approach it to resolve their problems will cause bouncing outcomes because the integrated APIs have not yet been analyzed.

To overcome the constant decline in standing business reputation, website performance must be without any resistance. APIs are responsible for catalyzing basic services of businesses, e.g., shipping, payment, security, etc. Therefore, accuracy in their performance can only be achieved through API testing mechanisms.

Best API Testing Tools For Developers

Based on the importance of API integration and its testing for transmitting reliable user experience or UX to customers, there’s a diversity of API testing tools present online. They are enough to let you take an X-ray examination of API performance. If these tests deliver expected outcomes, the API is approved to synergistically operate with the user’s intentions.

Out of the bulk of free/paid API testing tools available online, we’ve listed below the 17 most accurate tools to make your time super-quick in working with these fantastic analysis ninjas!

1. Katalon Studio

Katalon Studio is a comprehensive and precise toolset for website and mobile application automation analysis. It appears to hold a fine collection of compelling features, such as pop-up, iFrame, wait-time, and so on, to reduce basic complications in Web UI examination automation.

Key Features:

  • Well-organized and straightforward deployment, which directly lands testers to operate with the tool.
  • It assists testers to initiate trials, right after installation, with pre-built testing script templates.
  • Quick in progression and drive outcomes with details.
  • Manageable for non-technical testers.
  • Easy to operate and provide IDE configuration.


  • Not Open-source, but provides free usage.
  • However, for enterprise-level, the license is required with subscription fees of $76.

2. Karate DSL

Katalon Studio is a three-in-one API automation testing tool that examines precisely the measurements such as UI, mocks, and performance of the interface. It supports all protocols, including HTTP, JSON, GraphQL, and XML, and makes it suitable for all kinds of APIs. Also, for non-Java programmers, Karate DSL provides a separate platform to test those scripts written in languages other than Java.


  • Local assistance for both JSON and XML.
  • Robust payload statements including "deep-equals."
  • Data-driven examination.
  • Supposing even for non-technical members.
  • Combine JavaScript generators.
  • Test-doubles or HTTP mocking infrastructure.
  • Support retesting scripts as production inspections.
  • Context switching.


  • It has an open-source green flag of free usage.

3. Rest Assured

REST Assured maintains POST, GET, PUT, DELETE, OPTIONS, PATCH, and HEAD calls and can be applied to confirm and test the answer of these calls. REST Assured is used in Groovy and utili\es the constructor design to develop calls, organize headers, analyze the answers, and compare them with supposed output.


  • Highly supportive and easily manageable
  • Automate boilerplate code writing and make it HTTP connected.
  • Reduce the frustration of robotic outcomes.
  • Use Get, Given, When, Then, like notations to make outcomes human-readable.
  • Provide fewer efforts and more efficiency.
  • It supports DSL (Domain Specific Language) and makes tests behavior-driven.


  • It’s free to use and has no license-based entrance obligations.


SOAPUI permits analyzers to carry out automated API duties, regression, agreement, and pressure investigations on varied Web APIs. This tool assists all the quality protocols (HTTPS and XML) and technologies to examine all types of APIs. SOAPUI interface is uncomplicated that allows both programmers and non-programmers to work smoothly.


  • Enriched with Pro-functionality tests, including login, complex cases analysis, and more.
  • Provides data-driven testing techniques.
  • Support mocking and elaborate auto mock creation
  • Highly strict in analyzing security properties of APIs.
  • Lead performance validation testing by providing pre-build load strategies and click-and-run tests.


  • It’s open-source and provides free access.

5. Ping API

Ping API comes along with the comprehensive structure to initiate, progress, and terminate testing tasks in only three steps among the super-fast and super-easy API inspectors. After reaching the portal, users will simply have to introduce their API, test protocol, and key parameters; the tool will automatically write the script according to which initial report following the robotic report of faults list comes out.


  • Deeply inspect HTTP calls from request to response data.
  • Allow scriptwriting in Java and CoffeeScript format.
  • For non-technical members, it provides script generators.
  • Supports more than one script language and header key principles.
  • Easy to use and light to cooperate.


  • It’s free for 30 days and the premium plan comes with 20 projects testing per $50/month.

6. API Fortress

API Fortress is a codeless testing tool for thoroughly examining all types of APIs and has been introduced as a simple interface for both technical and non-technical developers.


  • Functional API investigation. Speed up or develop your consistent API analysis.
  • It supports tracking features while testing.
  • Authorizes the uptime, production, and functionality of active APIs.
  • Supports load testing and encourages testers to go through all freezy locations where storage crosses the red zone.
  • Implements critical testing protocols and lead mocking.


  • Free for a month only.

7. Paw (API tool for Mac users)

Paw is a full-featured HTTP tool that helps you examine and explain the APIs you develop or buy. It possesses an appealing native macOS interface to make calls, test server answers, produce client passes, and transport API introductions.


  • Deliver all types of HTTPS calls to analyze Mac centering functionality of API.
  • Use JSON Schema and thoroughly highlight the type of API tester using and explain it in-depth.
  • It never compromises teamwork ability from the user side and enables connection buttons.
  • Users can identify leggings in API, and through Paw, they can combine (by existing in a network) to impose changes.


  • The lifetime license subscription fee is $49.99.

8. Tricentis Tosca

Tosca’s API inspection permits developmental and non-developmental experts to efficiently develop, handle, and launch automated API analysis with a straightforward, no-code solution that ultimately anyone can practice and acquire.


  • Pre-built APIs can be examined.
  • Easy to tackle all improvement points.
  • Provide no-code solutions for better productivity.
  • Reduce maintenance time and fastly make analysis.
  • Support more than 200 APIs’ tests per minute.


  • It’s open-source, hence freely available.

9. RoboHydra Server

Robohydra is a web server-based API testing portal that helps users measure HTTP and HTTPS protocols for requests and responses. It allows mock interpretation and dynamic testing patterns for critical testing of APIs.


  • It reproduces a test script for perfectly fixing bugs.
  • Reserves proxy requests for analyzing special situations.
  • Users can make custom mocks to maintain code accuracy precisely.
  • Allows exploratory testing, which permits thinking beyond expected results.


  • It’s web-server testing tool that is available publicly for free.

10. HTTP Toolkit

HTTP Toolkit is an engaging and open-source (free) testing tool for debugging, critical interpretation, and operating with HTTP(S) on different devices, e.g, Windows, Linux & Mac. It contains certification for deeply describing all HTTPS protocols.


  • Fixed-term (monthly/annually subscription) logistic licensing.
  • Private or individual assistance.
  • Self-hosted frame.
  • Coaching & consultancy.
  • Multiple discounts on different features.


  • There are no charges required for beginners. Intermediates have $14/month, and Team-level subscribers have $22/month subscription fees.

11. Parasoft SOAtest

Parasoft is not ordinary or mediocre in performance, It’s a robust enough API testing tool, which is the latest category of interface examination means. It has the backbone of Artificial Intelligence and Machine Learning, which eliminates no manual efforts from users and lands them on spots where consideration is immediately required.


  • It transmits constant quality and updates based on in-depth observations.
  • Heterogeneous behavior for testing an API.
  • Supports Mobile and UI integration testing.
  • Load, performance, and data management testing.
  • Encourage security interpretation from start to finish.


  • It provides free entrance to its diverse case-study of specific tools testing.

12. Test Mace

For pro-developers who can’t compromise on API transparency and fast functionality with optimum quality, Test Mace is the best tool for them. It offers strict analysis rules to start investigation using variables, authentication, and syntax highlighting. For non-technicals, it also is amazing and provides graphical explanations.


  • Take complex tests and inquire by going into code adjustments.
  • Allow synergistic teamwork handling of APIs.
  • Autocomplete scripts and limit manual efforts.
  • Show javascript testing.
  • Support undo and redo changes for better negotiation.


  • It provides pocket-friendly monthly subscriptions from $4 to $8.

13. APIPray Inspector

Apiary permits tracking the API throughout the development duration by taking both call and reaction data. It enables the tester to compose API drafts and lets them survey Apiary director or


  • Character-based charge/handle over API reports.
  • It enables attaching and eliminating crew members from API perspective plans.
  • API Blueprint control dashboard.


  • It’s open-source and freely available.

14. ReadyAPI

ReadyAPI holds a detailed catalog of supportive possibilities based on analyzing REST, GraphQL, SOAP, JMS, and JDBC settings. With native combinations for the well-known tooling throughout the DevOps environment, you can control ReadyAPI's robust characteristic pool right into your CI/CD tunnel.


  • Promoting end-to-end API investigation to line up all the bugs to eliminate.
  • One-click advanced security scan.
  • Extract data from the server and modify it into synthetic data using ReadyAPI Data Generator.
  • Support API recording dashboard to align all the requests for testing.
  • Doesn’t involve script writing or script testing.


  • It doesn’t support open-source access.
  • The starting subscription fee is $749/year.

15. Postman

From debugging, exploratory analyzing, accelerating app development, and testing API automation, Postman provides an all-in-one and one-stop solution for all app development-related concerns. It’s considered the most professional testing tool, supporting more than a dozen types of testing tools inwardly.


  • It connects technical, non-technical, and analysts for accessing the same outcomes considering an API performance.
  • Supports all types of API request protocols including REST, SOAP, GraphQL, OpenAPI, RAML, Swagger, JSON, cURL, and WADL.
  • It tests changes, expectations, reliability, and functionality using different tools.
  • Immediately crawl the script and give an immediate solution for bug fixing and complications.


  • The subscription at individual level is $0.
  • From team to enterprise-level, the monthly license varies from $12 to $69.

16. Insomnia

Insomnia is an expert tool supporting the overall framework of API development and its configuration through testing. It turns down QA weight by re-employing test cases to develop an automated testing CI/CD tunnel for your APIs so you can examine whenever it's live.


  • Cross-platform connectivity and throughout the assistance.
  • Potential to test REST, SOAP, GraphQL, and GRPC API calls.
  • Capacity to collect, maintain, and accomplish REST API calls.
  • Aptness to put in order API calls in workspaces and sections.
  • Assistance for inquiry wire param deviser.


  • It’s free for catch-up work.
  • Subscription fees starters from $50/year.

17. vREST

Another extreme expert in its procedures, vREST carries out smooth testing procedures for API probed analysis. The API mocks can be performed in vREST, including the sustenance of Mock Server Functionality. Testers can immediately commence promoting the frontend utilizing mock HTTP calls.


  • It gives an all-inclusive tool to verify your REST APIs instantly
  • This rest API inspection tool presents zero-defect web applications with less resolution in API examination
  • No expertise devices are needed to verify your web app, and it can create documentation for your API terms.


  • Free for community use and drive $10/month enterprise subscription.

What Are The Benefits Of Api?

API comes where an application or website gets its professional interface to make higher reliability, UI, UX, and customer= retention. It's an acronym of Application Programming Interface that enables an application to communicate with other websites' servers or datasets. It develops long networking among multiple applications that make specific application functions, e.g., weather updates, temperature highlights, humidity records, etc.

For developers, APIs reduce their workload by providing shortcode commands that employ essential functions. If written manually, it can take a considerable time and money of both developer and hirer.

With API, the innovation factor appears to convey businesses to online communities differently but in attractive ways. Including each type of API, developer's communities are developed within business structures that are responsible for up-scaling the interface in such a way that truly makes sense for today's agile consumers.

How to Pick an API Testing Tool?

Based on the type of API built and the protocol for requests it uses, you can circle the best-matched API testing tool. Check out the features mainly supported by the tool and the subscription terms (whether the tool is free or paid), and if it’s paid, further check out similar tools (supporting same features), and compare the prices for annual or monthly plans. The best testing tool you can consider for all types of API testing is Postman. It offers annual subscriptions on feasible charges and is recognized worldwide for API’s most accurate analysis.

How Can I Test an Api?

For testing an API’s proper functioning or not, only a set of three steps require which mandates:

  • Send the request containing the information required to stimulate an action.
  • Collect the response and also data-driven through it.
  • Compare the collected information with expected results to measure how much the API is lagging to conceive an expected position of authenticity.

On this testing principle, all the testing tools work and deliver functionality and performance rate of API.

Why Is Api Testing Required?

API testing is required to determine whether an API is eligible to perform with the applications’ interface. API holds the position in apps to gather information from outer sources and then deliver it to users when required. In this way, APIs directly interact with customer intents and prescribe the reliability concentration for applications.

If an API is lacking basic code authenticity, it must not be integrated to get live. Testing tools come in this place to trace and eliminate all the faults linked with API’s performance and make your application 100% functional to cooperate with users exceptionally.


Over the last five decades, the rise of API has been recorded flooding, and the number of API Developers estimated under the software development domain increased approximately up to 19.1 million. It shows that the need for API this-party assistance for programmers expanded its worth by reducing their workload and presenting less-code commands with ultimate response-rate to add versatility in any platform.

But where the importance of adding APIs dominates other components in making applications fast, API testing in software development has also appeared as an essential factor alongside API development.