10 Best REST API Clients and Testing Tools for 2025

REST API Clients are tools used to send HTTP requests to interact with RESTful APIs, allowing developers to test, debug, and integrate APIs. They help build and send requests (GET, POST, PUT, DELETE) while handling responses like status codes and body content. These REST clients also support authentication methods and can automate testing. REST API testing tools, like Postman and Insomnia, are essential for ensuring API functionality, performance, and security.

Let’s talk about in detail about REST API Clients and Testing Tools below:

What is REST API?

An Application Programming Interface (API) establishes a connection between computers or between computer programs (applications) by providing readily available codes and information pipelines. It is a type of software interface that acts as a mediator among other pieces of software to streamline the interaction with one another.

How to Choose 10 Best REST API Clients and Testing Tools

Below is a comprehensive list of the 10 Best REST Clients that you can consider for API testing.

1. HTTPie

• HTTPie is a command-line HTTP tool written in Python that you can use to test your REST APIs. The built-in JSON support comes in handy for sending JSON requests. Read about other python REST frameworks in 2025.
  • Some of its key features are:
    • User-friendly.
    • Simple and natural syntax.
    • Built-in JSON support.
    • Syntax Highlighting.
    • Colorized output.

2. Postman REST Client

• Postman is a scalable API testing environment that allows you to test, debug, run requests, create automated tests, document, and monitor API. With Postman REST Client, you can create and send HTTP requests to a Development Server. 
  • Some of its key features are:
    • Seamless automated testing.
    • Collaboration features for effortless sharing and management.
    • Supports Swagger and RAML (RESTful API Modeling Language) formats.
    • Offers powerful visualization compatibility.
    • Supports multiple protocols, manages cookies, and manages certificates.

3. Curl

• Curl is an open-source command-line tool for transferring data to and from a Server.
  • Some of its key features are:
    • Allows you to send an application that is dependent upon HTTP.
    • Build a script with batch requests and execute them.
    • Supports different protocols like HTTP, FTP, IMAP, SMTP, and POP3.

4. Swagger

• Swagger is an open-source tool that will assist you through the entire lifecycle of an API. Swagger provides a standard format to create definitions of REST APIs.
  • Some of its key features are:
    • Supports API design, development, documentation, and testing.
    • Swagger provides many open-source tools for OpenAPI Specification.
    • Supports API mocking and virtualizations along with governance and monitoring.

5. Katalon Studio

• Katalon Studio is an automation tool that helps you automate your web, API, desktop, and mobile testing. Some of its key features are:
  • User-friendly UI for creating and managing your test.
    • Free API testing platform.
    • Requires no prior programming experience.
    • Supports all types of REST and SOAP requests.

6. SoapUI

• SoapUI is an open-source tool built specifically for API testing. With SoapUI you can test REST and SOAP APIs with ease.
  • Some of its key features are:
    • Drag and Drop functionality ensures scriptless functional testing.
    • Supports reusable scripts for load tests and security scans.
    • Supports different types of REST, SOAP, JMS, and IoT requests.
    • Supports seamless integration with 13 API management platforms.

7. REST-assured

• REST-assured is a popular Open-Source REST Client for testing API in Java. For Java developers, it’s a preferred way to test REST services easily and automatically.
  • Some of its key features are:
    • Allows you to write tests in clear and descriptive language.
    • Supports different types of XML and JSON requests.
    • Allows seamless integration with the Serenity Automation Framework.

8. Karate DSL

• Karate is an open-source API testing framework based on the cucumber library. It allows a tester to write meaningful tests in a domain-specific language for testing web services.
  • Some of its key features are:
    • Requires no prior programming experience.
    • It supports multithreaded parallel execution.
    • Allows testing and reports generation just like any standard Java Project.

9. Airborne

• Airborne is an open-source API automation tool used for testing REST APIs. It is a Ruby-based RSpec-driven framework. It doesn’t have a UI and provides the text file to write the code.
  • Some of its key features are:
    • Supports APIs written in Rails.
    • It can work with Rack applications.
    • To use this tool, you just need to know the fundamentals of Ruby and RSpec.

10. Apigee

• Apigee is a cross-cloud API testing platform for measuring and testing API performance.
• Apigee helps organizations create unified digital experiences for both older back-end services and fully serverless stacks.
  • Some of its key features are:
    • Customizable Developer Portal.
    • Supports Node.js.
    • Open API Specification allows easy creation of API proxies.
    • Allows you to design, monitor, analyze, and scale APIs.

Conclusion

API is a bigger umbrella, and REST API is a unique type of API prevalent among cloud applications. REST APIs are all about communication. You have your Web App or Web Page communicate with a Cloud-Based Server via a REST API. But new developers find REST API difficult because it fails to maintain the state within sessions. This article introduced you to REST APIs, their need, and their importance. The article later took you through the 10 Best REST Clients that you can consider for API Testing.

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