No Code API automation – API Monkey

4 Free Tools to Test your Rest API Easily

Application Programming Interface (API) refers to a set of programming instructions for interacting with a web-based software application. API testing is a type of software testing that determines whether the created APIs meet the application’s functionality, performance, reliability, and security requirements.

The majority of API testing is still done manually, despite the fact that test automation is currently mostly used for UI. Manual testing is a time-consuming and error-prone process that can be avoided with the use of test automation software. API automation tests, on the other hand, are key components of successful testing.

So, here is a list of the top four free API testing tools that will help you get your work done faster, more effectively, and for less money.

1. Postman

Postman is an API platform that allows you to create and use APIs. Postman is used by over 15 million developers because it streamlines collaboration and simplifies each phase of the API lifecycle, allowing you to design better APIs faster. Postman is an HTTP client that uses a graphical user interface to test HTTP requests, allowing us to acquire various types of replies that must then be validated.

Postman also allows us to build alternative environments by generating/using variables, such as a URL variable for different test environments (dev-QA), which allows us to run tests in different contexts using existing requests.

Postman is an easy-to-use application that helps us save time when running tests. The collecting feature and the ability to build different testing settings are two of Postman’s advantages.

The latest version of Postman available is Version 8.12.1

The common methods used in Postman are:

  • GET: Obtain information 
  • POST: Add information
  • PUT: Replace information
  • PATCH: Update certain information
  • DELETE: Delete information

The most common response codes in Postman have been classified into 4 series:

  • 100 Series: Temporal responses.
  • 200 Series: Responses where the client accepts the request and the server processes it successfully.
  • 300 Series: Responses related to URL redirection.
  • 400 Series: Client error responses.
  • 500 Series: Server error responses.

For more details on return types and response codes, see REST API Return Types.

2. Insomnia

Insomnia is a free cross-platform desktop application that makes interacting with and building HTTP-based APIs as painless as possible. Insomnia blends a user-friendly interface with complex features such as authentication aids, code creation, and environment variables.

  • You can easily categorize your requests to match your workflow or API data model. 
  • Without switching applications, you can make, organize, share, and execute any REST, SOAP, GraphQL, or GRPC requests directly from Insomnia.
  • For a seamless development/production workflow, you can handle numerous environment variables such as authentication credentials, tokens, or session IDs for re-use worldwide or within a public/private environment.
  • To help you get to market faster, Insomnia generates code snippets in popular languages like Curl, NodeJS, Go, Swift, Python, Java, C, and more.
  • The specification editor built into Insomnia allows you to take a design-first approach to API development.
  • You can preview API designs in real-time, allowing you to make changes without switching applications or views.
  • To centralize API tests, assure valid API functioning, and enhance development productivity through CI/CD pipelines, you can use Insomnia Test Suites to create functional API tests.
  • Build unique CI/CD API pipelines that fit with your existing processes by seamlessly integrating with Git providers like Github, Gitlab, and Bitbucket.

Insomnia allows you to import a variety of file kinds. Insomnia, Postman v2, HAR, OpenAPI, Swagger, WSDL, and Curl have now supported formats. Workspace, environment, request group, and request are the resource categories that can be imported and exported.

Insomnia is most known for showing text content such as JSON and XML, but it can also display rich content such as HTML, pictures, SVG, audio files, PDF, and CSV.


cURL stands for client URL, and it’s a command-line tool that allows developers to send and receive data from a server. cURL is a software project made up of two separate development projects: cURL and libcurl. Because cURL is based on libcurl, it supports the same set of Internet protocols as libcurl.

cURL Command Tutorial with Examples - Boolean World

cURL operates on practically every platform and supports a variety of protocols, including HTTP and HTTPS. As a result, cURL is perfect for testing communication between practically any device, from a local server to the majority of edge devices.

cURL is extremely portable and works with nearly every operating system and connected device. cURL may be rate controlled and offers robust error logging.

cURL is also found in automobiles, television sets, routers, printers, audio equipment, mobile phones, tablets, setup boxes, and media players, as well as serving as the Internet transfer engine for thousands of software applications in over 10 billion installations.

The URL from which we would like to retrieve data is followed by the curl command. For example, curl

The most common HTTP methods used in cURL are GET, POST, PUT and DELETE.

-d ‘{“name”: “saisha”, “job”: “engineer”}’

  • PUT is a command that allows you to create or update a resource. This could be used to update the contents of a file or to create or update a record in a database.

-d ‘{“name”: “john”, “job”: “marketing management”}’

4. SoapUI

The Simple Object Access Protocol (SOAP) stands for Simple Object Access Protocol. Web service inspection, invocation, development, simulation and mocking, functional testing, load, and compliance testing are all covered by its capabilities. 

SoapUI is the first open-source tool built for both developers and testers that spans the complete testing spectrum (functional, security, load, and mocking). With its simple graphical interface, SoapUI is the starting point for API testing, allowing you to quickly check REST and SOAP-based web services.

Testing Your First REST API In SoapUI
  • Scriptless Functional Testing: You can construct and run even the most complex scenarios with drag and drop test generation.
  • Security Testing: Protect your website services against the most prevalent security vulnerabilities with a combination of tests and scans.
  • Load Testing: Create load tests fast and efficiently using existing functional API tests as a foundation.
  • API Mocking: Without having to wait for your Real Web Services to be available or accessible, you can imitate them. The best part is that you won’t have to invest in costly full-scale replicas of your production systems.
  • Protocol Support: SOAP/WSDL, REST, and JMS
  • Vibrant Community Ecosystem: The open source community and partners that surround SoapUI are a significant part of what makes it so fantastic.

ReadyAPI is an API-ready platform that contains a test module for the next generation of SoapUI. ReadyAPI is a next-generation API testing solution that allows development and testing teams to construct, run, and analyze complex validation of REST, SOAP, and GraphQL APIs, as well as JMS, JDBC, and other web services.

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