12 Free Tools for Testing, Design and Development of API

API testing

Before we start, let us have an understanding of the term, ‘API’.

Commonly referred to as an Application Programming Interface, an API system, in computer programming is basically a super set of program instructions packaged as a unit that perform a specific task, a set of communication rules computers use to communicate with each other and a certain set of tools that are used to build software and applications.

Whether be a web-based system, an operating system or a database system, an API eases to develop applications for a particular system using a given programming language.

It comes in the form of libraries, SOAP or REST services. Whatever be its format, its duty is to help applications and software to access databases and computer hardware, ease the work of programming the GUI components and assist distinct applications to share data.

So, we can clearly see, an API is basically the foundation to any well functioning software or application and must be precisely designed, developed and thoroughly tested. For this, a variety of tools are available in the market. But, not all solve the purpose.

API testing

Here is a list of most deliberately sorted 12 free tools for testing, designing and development of API.


Solely designed for testing purposes, it is indeed the market’s most easy to learn tool which covers all elements or aspects of functional testing. Not only is it an easy to go tool, but also meets your business requirements and time frames all under one roof.

Major features include-

  • Putting dynamic and realistic data to your API tests to give you an environment to better comprehend the ways how your consumers interact with your API in the real world.
  • Checking complex APIs by creating test plots to simplify advanced functionality.
  • Automating the testing procedure by using the API Discovery feature which not only finds you a suitable API, but also generates test structures for them.

SoapUI NG gives you a free trial fro 14 days and then you upgrade your plan to SoapUI NG PRO. You may choose the monthly or yearly plan as per your need.


Looking for speed and reliability? Known for its lesser downtime and faster resolution time, Runscope also informs you when your APIs go down before your customers do with the help of its already inculcated various webhook notification tools. It also tests and monitors both public as well as private APIs to quickly catch and debug errors with its on-spot agents thus ensuring optimum performance of your API at all times.

Its main features are-

  • Verifying that your APIs return the right data.
  • Logging crucial API transaction failures when they happen.
  • Compartmentalizing the testing by automatically running API tests and notifying the right team, the moment an error occurs.


Mainly renowned as a designing tool, Apiary not only designs, but also prototypes, documents and tests your APIs. Famous among team developers, this tool with its GitHub sync helps you to build great APIs with an effective collaboration from developers, testers, architects, product managers, clients, and partners from both inside and outside your organisation or team.

Its main features are-

  • Presence of a management dashboard for API blue-prints and a dedicated , web based team to cater to your queries.
  • Gives access control over APIs on a role basis.
  • Helps to easily add or remove members from your API design projects.
  • Customised settings for provisioning of a new team member and API blueprint visibility.


If your forte is in REST APIs, then vREST is just the tool for you. It excels is simplification and automation of REST API testing. Famous as a multi-platform tool, it is best suited for any type of web applications, mobile applications as well as desktop applications. Additionally, it has a chrome plug-in that helps to quickly create test cases for recording interactions with and responses from your API.

Its major features include

  • Recording all your test cases to tweak them with custom validators and variables and then replaying them again for better accuracy.
  • Separating the frontend from the backend to help them work parallel and hence boost up your web development procedure.
  • Eye-friendly reporting of expected vs actual results.


Sounds a bit deliverish, but yeah, this tool is the best for developing your APIs quickly, especially when you are in a time frame. It’s major advantages are-

  • Quickly construct requests and hence build workflows using its Collections.
  • Customize your own API test cases to response data and response time and much more.
  • The Run button allows you to test public APIs at just a one-button click.


As their tagline says- “The most complete platform for API developers”, Restlet indeed helps you to create, test and run your own API in 3 simple steps.

  • Helps you to design your API contract, automatically create implementation skeletons and fully test your API after completion. On an average, it provides you with a complete package of tools to quickly and easily design as well as build your API.
  • Starting from providing SDKs for various platforms to calling poorly documented APIs with improper contracts, this comprehensive and integrated tool helps you to discover, test and consume your API.
  • Irrespective of your location, this tool provides access rights, analyzes usage and manages users to provide them with client SDKs, discovery features and API documentation.


If you need to test the performance of your API, you are looking at the right tool. It lets you run open source based performance tests for your API and thus validates your APIs performance at every software delivery stage.  Benefits include-

  • Helps you to run realistic mobile tests on real devices, and also record and create your tests.
  • Helps to shape your load profile to show connections like 3g,LTE, WiFi in the real world, and also allows you to set your own custom latency and bandwidth properties.


Did you just get caught with a broken API? You may not be using the right tool. Thanks to API-metrics that helps you to track each and every aspect of your API. With its API and cloud service monitoring, this tool specialises in giving you detailed statistics and immediate alerts to help you control your API in a more user-friendly as well as interactive way.

The pros of this tool are-

  • Helps to create complex API calls and position it anywhere on your map.
  • Has a variety of custom dashboards that allow you to create your own customizable performance reports.
  • Facilitates building of mixed Workflows which comprises of REST and SOAP APIs.


Inspection of any HTTP API call with complete request and response data is the main forte of the Ping-API. Java Script and Coffee Script are the programming languages supported in this tool.  Even if you don’t have any clue about these programming languages, this tool’s generator gives you your test script upon setting your API parameter. Its virtues are-

  • Notifies you when your web application is down or is unresponsive.
  • Allows you to validate your login info even after you deploy your web application.

API Garage

Time for teamwork and business ? Well, it’s time for API Garage. This tool helps to collaborately create designs for your API. It is also helpful to create business cases for your API applications. Even if API building is not your forte, this tool helps you focus on your business while its developers build your API. It also has a 3-day API certification to help the amateurs implement an API for their business. This tool further helps you to integrate the proper tools for designing, developing, delivering, testing and monitoring your API. Moreover, its rating system helps you to understand where your API stands in the global market and thus helps you to improve your API.

API Transformer

Website designing requires expertise. With a cute logo that reminds us of the “Transformers”, and a very “to the point” website, this web-based tool allows anyone to convert their API files across different formats. We all know, working with different clients and having to learn RAML, APIBlueprint and IODocs is quite a headache. So, no more excuses not to design or model your APIs just because of slient-format issues. With this simple yet crucial tool, you can now transform API descriptions from/to various formats e.g.,Swagger, API Blueprint,RAML, WADL, Google Discovery, I/O Docs.


Nothing is more embarrassing than to have a public-facing API that breaks down the minute it goes online because you didn’t test how well it held up under heavy load. Loader.io is what comes to your rescue. You can now set up a target host’s endpoint via Loader.io’s API, and test the results via a browser page in real time.

Out of thousands of API tools, these were some that will help skilled as well as amateur programmers to test, design as well as develop their API as per their requirements.

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