Best Software for API Testing in 2025

In 2025, software systems are increasingly reliant on APIs to connect services, applications, and platforms. Whether you’re building a SaaS product, a mobile backend, or a microservices-based architecture, API testing has become a critical part of the development lifecycle.

Choosing the right API testing tool is essential for ensuring stability, performance, and security. In this guide, we explore the best software for API testing, highlighting tools that help developers, testers, and DevOps teams automate and optimize their API validation workflows.

Why API Testing Matters

APIs are the glue that connects modern applications—but they’re also a common point of failure. Without proper testing, issues like incorrect data, broken endpoints, and security vulnerabilities can go unnoticed.

Key benefits of API testing:

• Detect issues before they reach production

• Validate business logic independently of the frontend

• Ensure consistent performance under load

• Simplify CI/CD pipeline integration

• Test authentication, data flows, and error handling

Best Software for API Testing in 2025

1. Postman

Postman is the most popular tool for API development and testing. It offers a comprehensive suite for sending requests, scripting tests, and managing environments, making it ideal for developers and QA engineers alike.

Key Features:

• User-friendly interface for building and sending API requests

• Support for REST, SOAP, and GraphQL

• Automated test scripts using JavaScript

• Collection runner for automated test workflows

• Collaboration features for teams and shared environments

2. Insomnia

Insomnia is a lightweight, open-source API client focused on fast workflows and performance. It’s designed with developers in mind, especially those who work with REST and GraphQL APIs.

Key Features:

• Clean UI with fast request building

• Support for REST, GraphQL, and gRPC

• Environment variable support for dynamic testing

• Request chaining and test assertions

• Open-source with plugin support

3. SoapUI

SoapUI by SmartBear is a dedicated API testing tool that supports both REST and SOAP services. It’s favored in enterprise environments for its robust automation capabilities.

Key Features:

• Drag-and-drop test creation for complex scenarios

• Supports data-driven testing

• Scripting with Groovy for advanced test logic

• Integration with CI tools like Jenkins

• Commercial and open-source versions available

4. Katalon Studio

Katalon Studio is a low-code automation testing platform that supports web, mobile, and API testing. It’s ideal for teams looking for an all-in-one solution.

Key Features:

• Unified test automation for UI and APIs

• Supports REST, SOAP, and GraphQL

• Data-driven testing and assertions

• Built-in test reports and analytics

• CI/CD integration with Jenkins, GitLab, etc.

5. Hoppscotch

Hoppscotch is an open-source alternative to Postman built for speed and simplicity. It’s fully browser-based and focused on fast API testing and debugging.

Key Features:

• Web-based interface, no installation needed

• Real-time API request/response testing

• Support for WebSockets, SSE, and GraphQL

• Environment and request history support

• Completely open-source and community-driven

6. ReadyAPI

ReadyAPI is the commercial counterpart of SoapUI and offers advanced testing features geared toward performance, security, and automation.

Key Features:

• End-to-end API functional, load, and security testing

• Comprehensive reporting and data visualization

• Smart assertions and test coverage insights

• Advanced CI/CD support

• Designed for enterprise-level automation

7. REST Assured

REST Assured is a Java-based library used for testing REST APIs. It’s powerful for backend developers writing unit and integration tests in Java.

Key Features:

• Seamless integration with Java and JUnit/TestNG

• Supports JSON and XML validation

• Authentication and parameter testing support

• Simple syntax for request chaining

• Best suited for code-centric workflows

8. JMeter

Apache JMeter is primarily known for performance testing, but it also supports functional API testing. It’s ideal for load testing APIs under stress.

Key Features:

• Load and performance testing for REST and SOAP

• CLI support for integration into CI/CD pipelines

• CSV data-driven testing

• Scripting via Groovy and Beanshell

• Detailed test reports and graphs

9. Karate DSL

Karate is an open-source tool that combines API test automation with BDD (Behavior-Driven Development). It allows for readable test scripts using simple syntax.

Key Features:

• BDD-style syntax for writing tests

• Built-in support for JSON and XML assertions

• Supports parallel test execution

• API, UI, and performance testing in one framework

• No Java code needed to start testing

10. Cypress (for API Testing)

While Cypress is mainly known for frontend testing, it also offers powerful support for API testing, especially in end-to-end test scenarios.

Key Features:

• Integrated with frontend and backend workflows

• Native JavaScript support

• Test APIs before and after UI interactions

• Works well in CI/CD pipelines

• Detailed error tracking and debugging tools

Comparison Table

How to Choose the Right API Testing Software

Different teams have different needs. Here’s how to narrow it down:

• Developers and quick testers: Postman, Insomnia, Hoppscotch

• QA professionals: SoapUI, Katalon, ReadyAPI

• Code-centric teams: REST Assured, Karate, JMeter

• Teams needing full automation: Katalon, ReadyAPI, Cypress

• Budget-conscious or open-source focused: Hoppscotch, Karate, JMeter, Godot

Also consider:

• Your programming language preference (e.g., Java for REST Assured)

• Team size and collaboration needs (Postman, Katalon)

• Type of APIs (REST, SOAP, GraphQL, gRPC)

• Desired test depth (functional, performance, security)

Conclusion

The importance of robust API testing in modern development workflows cannot be overstated. Whether you’re building an internal microservice or a global SaaS platform, having the right toolset ensures reliability, scalability, and user trust.

From intuitive GUIs like Postman and Insomnia to full-scale automation platforms like Katalon and ReadyAPI, this list of the best software for API testing gives you the foundation to select the right tool for your technical stack and workflow needs.