I have been dealing with API development and testing for quite some time now. I have played around with lots of different tools, as there are dozens of them these days. Some of them are quite good, powerful and beautiful indeed. Switching from one tool to another, I faced various problems and disadvantages, most of which I was able to solve.

Here are some top four API client and testing tools that are very best for use especially when creating and testing your API:

1. Postman


Postman helps you to be more efficient while working with APIs. You can build, test, and document your APIs faster, and share your work with other developers. It is much more handy and easier to use than Fiddler and SoapUI.

Postman makes API development faster, easier, and better. The app is used by more than 3.5 million developers and 30,000 companies worldwide. Postman is designed with the developer in mind, and packed with features and options that allows for testing and seamless development.


  1. Amazing and easy to use user interface.
  2. Allows for automated testing
  3. Easy request building.
  4. Auto generation of some sample code
  5. Supports collaboration and sharing.
  6. Supports chaining of requests  


  1. Very heavy and uses a lot of system resources

Learn more on postman and how to use it here

2. cURL


Curl (or cURL), on the other hand, is a small but powerful tool for transferring files and data over URLs. On a smaller scale, it’s great for testing REST APIs. And, though most web developers might opt to use other tools such as Google’s Postman, cURL is done in the command line and can leave you feeling like a true computer hack.

CURL stands for “client” and “URL”, since it is a program run on the client side that makes HTTP requests to URL’s. Since it’s open source, you can download it here. Or if you have Gitbash already installed on your machine, it’s automatically included.

Download Curl here

3. Insomnia


Insomnia is a free cross-platform desktop application that takes the pain out of interacting with HTTP-based APIs. Insomnia combines an easy-to-use interface with advanced functionality like authentication helpers, code generation, and environment variables. There is also the option to subscribe to a paid plan to gain access to encrypted data sync and team collaboration.


  • Easy for switch between environments with separated variables
  • Ability to reference response values of other requests
  • Generate code snippets to almost any language your want
  • Unlimited installations with Free plan
  • Available for Mac/Windows/Linux App and Google Chrome extension
  • Open source!


Download Insomnia here

4. TestMace


TestMace is pretty much new into this list since it’s currently into its alpha test stage. Anyway, after trying it for some time, I can pretty much say it a good one since it offers pretty much what a beginner would need while testing his/her APIs and its super light.


  1. Variables mechanism, that allows to define both global and node scoped variables. Variables help to store and reuse any data in any part of the app in the same way.
  2. Syntax highlighting and autocompletion



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