Effective Strategies 7 min read

Top 5 REST API Testing Tools for Testing ( Free)

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. Comparing the Top 5 REST API Testi

Top 5 REST API Test Tools: Streamline Your Testing Process

REST API has become the preferred method for building web applications due to its flexibility, and scalability. However, testing these APIs can be a daunting task as they involve complex data and multiple APIs.

Fortunately, there are numerous free REST API testing tools that 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.

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.

Comparing the Top 5 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, and Rest-Assured. Amidst these well-established contenders, a new player, Apidog, has emerged.


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. Apidog 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.

The Key Features of Apidog:

  • An intuitive user interface for easy navigation and learning
  • Powerful automation and CI/CD pipeline integration
  • Real-time collaboration features for team projects
  • Seamless integration with popular tools like GitHub and Jenkins
  • Cloud-based platform for easy access and maintenance
  • Advanced reporting for in-depth performance analysis and optimization


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.

The Key Features of Postman:

  • Widely used with an intuitive interface and extensive features
  • Strong collaboration features through shared workspaces
  • Collection Runner for limited test automation
  • Integrations with CI/CD pipelines require additional setup and configuration
  • Offers a desktop application and a web-based version
What is Postman (A Tutorial for Beginners)
What is Postman? This article will provide a comprehensive introduction to Postman, so let’s get started.

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.

The Key Features of Swagger UI:

  • Mainly focused on API design, documentation, and development
  • Provides a visual interface for designing and documenting APIs
  • Offers basic API testing features but not as extensive as dedicated testing tools
  • Integrates with various API development tools and frameworks
  • Lacks advanced testing features like automation and performance analysis
Mastering Swagger UI: A Step-by-Step Tutorial for Developers
Swagger UI is an open-source tool for visualizing and interacting with RESTful APIs. In this tutorial, we’ll show you Swagger’s basic introduction and how to use Swagger UI to Document and Test an API.


JMeter is a popular open-source tool 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 JMeter, users can easily create, configure, and execute API tests to measure performance and identify potential issues that may arise under different scenarios.

The Key Features of JMeter:

  • It is primarily a load and performance testing tool but can also be used for functional API testing.
  • Requires the user to understand its components and create test plans manually
  • Supports multiple protocols, including HTTP, FTP, and WebSockets
  • Highly extensible through custom plugins and scripting
  • Lacks a user-friendly interface and collaboration features


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:

  • Open-source Java library for REST API testing
  • Requires knowledge of Java programming and testing frameworks (like TestNG or JUnit)
  • Offers powerful and flexible testing capabilities
  • Integrates easily with CI/CD pipelines and build tools like Maven and Gradle
  • It lacks a graphical user interface and can be less accessible to non-developers

A Step-by-Step Guide to Integrate 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

  • Visit the Apidog website.
  • Select the 'Sign Up' button in the web page's upper right section.
  • Fill out the registration form with your email, username, and password. Alternatively, you can sign up using your Google or GitHub account.
  • Once you've signed up and logged in, you'll be directed to the Apidog dashboard.
Apidog Website

Step 2. Create a New Project

  • Click the 'Create Project' button on the Apidog dashboard.
Create a New Project
  • In the 'Create Project' dialog, write the project name as Project Name: JSONPlaceholder API.
Project Name
  • Click 'Confirm' to proceed.

Step 3. Add Your API

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.

  • Click the '+ Add API' button.
Add Your API
Request URL
  • Click 'Save.'
Save 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.

  • To add a query parameter, click the '+ Add' button in the 'Query Params' section, and enter the parameter name and value.
Apidog's Params
  • To add a header, click the '+ Add' button in the 'Headers' section, and enter the header name and value.
  • To add a request body, select the appropriate content type (e.g., JSON, XML, or form data) and enter the request body data.
Request Body

Step 4. Define the API Response

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

  • Click 'Add Response' and enter the following information in the 'Add Response' dialog:
  • Status Code: 200
  • Description: OK
  • Under 'Response Body,' click the 'Add Schema' button.
Add Schema
  • Define the response schema using the JSONPlaceholder API documentation as a reference. For the 'Get All Posts' endpoint, the response schema should look like this:

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

  • Click 'Save.'

Step 5. Test the API

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

  • Click the 'Send' button in the 'Request' tab.
  • Verify that the response data matches the defined schema and that the status code is 200. The 'Status' and 'Time' fields in the 'Response' tab will show the request results.
Test Result

Step 6. Share and Collaborate

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.

  • Click the 'Share' button in the top right corner of your project dashboard.
  • Click '+ New Share.'
  • Configure the sharing settings as desired, such as allowing others to edit or view only, and select the appropriate environment for your API documentation.
New Share
  • Copy and distribute the share link to your team members or stakeholders.
Got All Post


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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