Top 10 REST API Testing Tools for Testing

Many free REST API testing tools can help streamline the process and ensure high-quality end products. In this article, we will introduce you to the top 5 free tools for REST API testing that can help you accelerate your API testing workflow, reduce bugs, and achieve better application performance.

Ahmed Waheed

Ahmed Waheed

16 May 2025

Top 10 REST API Testing Tools for Testing

Robustly testing REST APIs is critical for identifying defects and validating functionality before release. Many REST APIs for testing tools like Postman, SoapUI, and Apidog exist to support REST API testing needs like performance monitoring, automated validations, and test reports.

This guide provides an overview of leading free and commercial solutions, including the Apidog online API tester. It compares key features, integrations, and pricing models to consider when selecting a free REST API testing platform.

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What is REST API Testing Tool?

REST APIs enable communication between applications using HTTP requests. Testing tools like Postman and SoapUI validate that REST APIs function as expected. Key features include building requests, validating responses, reusable test cases, mocking, and performance testing.

API testing verifies endpoints handle inputs correctly, return expected status codes and data structures, conform to specifications, and perform well under load. Automated API testing catches issues early and ensures changes don't break integrations.

Best 10 REST API Testing Tools

The market is flooded with numerous API testing tools, making it difficult to decide which fits your needs. Let's briefly compare some popular REST API testing tools: Postman, Swagger, JMeter, Rest-Assured, etc. Amidst these well-established contenders, a new player, Apidog, has emerged.

Apidog

Apidog is a comprehensive solution that caters to various roles in a development team, including API designers, back-end developers, front-end developers, and QA engineers. This API testing tool like Postman enables collaboration, automates mocking, simplifies debugging, and generates beautiful API documentation.

With its user-friendly interface and rich feature set, Apidog is the perfect tool to streamline your API testing process. Check this video in detail.

The Key Features of Apidog:

How to Create and Test a REST API in Apidog?

This guide will delve deeper into integrating a REST API in Apidog using the JSONPlaceholder API, a free online REST API that returns JSON-encoded data for testing and prototyping. The JSONPlaceholder API provides several endpoints for manipulating data, such as posts, comments, albums, photos, todos, and users.

Step 1. Sign Up for Apidog

Step 2. Add Your REST API Request

Once your project is created, add the REST API endpoints. In our example, we'll add the endpoint for fetching all posts from the JSONPlaceholder API.

Define the API Request Parameters (Optional)

If your API requires query parameters, headers, or other request data, you can define them in the 'Request' tab.

Apidog's Params
Header
Request Body

Step 4. Define the API Response

Once you've added the endpoint, it's time to define the expected response.

Add Schema

[ { "userId": 1, "id": 1, "title": "sample title", "body": "sample body" }]

Step 5. Test the REST API

Now that the API is defined, you can test it to ensure it works as expected.

Test Result

Step 6. Share and Collaborate with team members

Apidog allows you to share your project with team members or other stakeholders. You can also generate documentation to make it easier for others to understand and use your integrated REST API.

Postman

Postman is a widely used REST API testing tool known for its user-friendly interface and robust functionality. It allows users to easily create, test, and document APIs through features such as automated testing, test suites, and API documentation. With Postman, developers and testers can easily organize and manage their APIs, test their functionality against various scenarios, and share them with their teams.

Postman

The Key Features of Postman:

Swagger UI

Swagger UI is an open-source tool used for testing REST APIs and documenting them in a standardized format. It provides an interactive user interface that enables developers and testers to create requests and receive responses from the API. Its integrated documentation feature allows users to keep track of their API's endpoints, parameters, and responses.

Swagger UI

The Key Features of Swagger UI:

Apache JMeter

JMeter is a popular open-source API tester for load and performance testing that can also be used for REST API testing. JMeter's user-friendly interface and extensive functionality make it an excellent choice for testing large, complex systems or applications with a variety of configurations. With Apache JMeter, users can easily create, configure, and execute API tests to measure performance and identify potential issues that may arise under different scenarios.

JMeter

The Key Features of Apache JMeter:

Apigee

Apigee is a comprehensive API management platform developed by Google Cloud. It provides a robust set of tools and services for designing, deploying, securing, and monitoring APIs. Apigee enables organizations to create, publish, and manage APIs across their systems and applications.

Key Features of Apigee:

SoapUI

SoapUI is a popular open-source software tool primarily used for testing SOAP and REST-based web services. It provides a comprehensive set of features for functional testing, load testing, and mock service creation. SoapUI is widely adopted by developers and testers due to its user-friendly interface and extensive functionality.

SoapUI

Key Features of SoapUI:

Katalon Studio

Katalon Studio is a comprehensive test automation solution that supports testing for web, mobile, and API applications. It offers a user-friendly interface and a wide range of features for test creation, execution, and management. Katalon Studio is particularly useful for testing REST APIs and integrates well with popular CI/CD tools.

Katalon

Key Features of Katalon Studio:

Rest Assured

REST-assured is an open-source Java library used for testing REST APIs. It allows users to write tests using Java, giving them access to a wide range of libraries and tools. REST-assured provides a simple and intuitive way to test APIs using features such as error validation, authentication, and parameterization. With REST-assured, developers and testers can easily set up and run API tests using industry-standard testing frameworks such as JUnit and TestNG.

The key Features of REST-assured:

Insomnia

Insomnia offers a simple way to send requests and view responses as a popular API tester. It is completely free with support for cookies, OAuth2 authentication, environments, test scripting, and more. Insomnia's clean and elegant interface makes it great for API developers to quickly test.

Insomnia

Key Features of Insomnia

Runscope

Runscope is a cloud tool for testing and monitoring APIs globally. Its features include auto-generating tests, testing webhooks, debugging APIs, and integrating with services like Slack and PagerDuty.

Runscope

Key Features of Runscope

Conclusion

In conclusion, REST API testing is a crucial part of software development, ensuring the quality, performance, and functionality of APIs. The five free REST API testing tools discussed in this blog - Apidog, Postman, Swagger UI, and REST-assured - provide a robust range of capabilities and features that can help developers and testers streamline their API testing workflows and improve their end-products.

Whether you're new to API testing or an experienced professional, these tools can help you in your testing endeavors, saving time, reducing bugs, and ultimately leading to a better user experience.

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