API testing is a critical piece of the development cycle, offering a pathway for validating and improving code at scale. What is arguably as important as the cycle itself is the tooling used within the cycle — a good suite of tools can result in incredible progress and quality, while poor tools can reduce efficiency and turn your testing process into a barrier in and of itself.

Today, we’re going to take a fresh look at the state of API testing tools in 2025. These ten tools are considered top of the class, offering powerful implementations for testing a variety of codebases, implementations, and systems. While this list is certainly not exhaustive, it represents some of the best options currently on the market. Let’s dive in!

1. Postman

Postman has become a staple in the API world for good reason. Its UI makes API testing approachable, and its ecosystem supports everything from quick manual requests to automated test runs. It’s great for teams looking to collaborate through shared workspaces and collections, though power users will be boxed in when test logic gets complex. It’s not the most scalable tool for deeply programmatic testing, but it nails the basics and then some.

Benefits

• Postman offers an intuitive GUI for rapid API testing, opening up testing to more teams and diverse contributor types.
• Additionally, it offers extensive support for REST, GraphQL, and gRPC, allowing for a wide inclusion of codebases and implementations.
• Its large community and ecosystem of plugins and integrations expand this support significantly.
• The collections and workspaces feature rounds off this extensible presence with support for collaborative development.

Drawbacks

• While it handles basic testing pretty well, complex workflows can become cluttered and hard to maintain.
• Postman also has relatively limited support for performance testing.
• These issues make it not ideal for deep assertions or multi-step test logic compared to native integrated systems.

2. Katalon Studio

Katalon Studio is a surprisingly robust solution that wraps together API, UI, and mobile testing into a single low-code platform. It’s accessible for testers with limited scripting experience, but still powerful enough for DevOps pipelines. The tooling is pretty good from day one, with reporting, analytics, and CI integrations right out of the box. That said, the more advanced your use case, the more likely you’ll bump into the constraints of the platform’s abstractions.

Benefits

• Katalon can test REST, SOAP, and GraphQL APIs, offering comprehensive support.
• Its low-code environment enables quick onboarding and opens up contribution to marketing, sales, and other teams.
• It offers built-in analytics, reporting, and test orchestration, as well as strong integration in CI/CD and cloud platforms.

Drawbacks

• While Katalon is a more inclusive solution, this simplicity means that things feel a bit more locked down and less customizable than other options.
• Even though it’s more streamlined, it can still feel heavy for simple testing needs, creating a very specific niche where it fits.
• Licensing costs for advanced features can mean that teams looking for a simple solution can be hit with a significant bill just for basic testing.

3. SoapUI/Ready API

SoapUI is one of the original solutions for API testing. It’s a bit old-school in terms of the interface and scripting style, but it’s incredibly feature-rich, especially when paired with its enterprise-targeted ReadyAPI solution, which bundles SoapUI with some additional proprietary and open source tools. You’ll get functional, security, and load testing in one place, though be ready to roll up your sleeves and write some Groovy if you want to do anything dynamic.

Benefits

• This tool is relatively mature, and as such, offers comprehensive support for API paradigms, including REST and SOAP, as well as other complex systems.
• Strong scripting capabilities are provided with the Groovy language, unlocking control and automation.
• ReadyAPI, the paid version of this tool, includes advanced features for large teams needing more comprehensive systems.

Drawbacks

• This tool has what many would consider to be an outdated UI. Even ignoring that, it has quite a steep learning curve, which can make effective utilization difficult.
• Large testing suites can have performance and stability concerns.
• The SoapUI implementation is a limited open-source version compared to the enterprise-ready implementation in ReadyAPI.

4. Apache JMeter

Apache JMeter is a workhorse for performance testing, with protocol support that goes beyond just HTTP. It’s dependable, scriptable, and extensible with a rich plugin ecosystem, offering a good deal of flexibility. It’s also pretty clunky for specific flows — while it can handle functional testing, that’s not really where it shines, and teams might find it wanting for day-to-day validation.

Benefits

• JMeter is pretty robust, offering great support for load and performance testing.
• This tool is open-source and widely adopted, and has solid and extensive plugin support and CI/CD integration.
• JMeter supports a variety of protocols beyond HTTP, allowing for more flexible testing.

Drawbacks

• JMeter’s GUI is not beginner-friendly, creating some steep learning curves for first-time users
• It can be challenging to manage and debug complex test flows, creating a barrier for teams.

5. Rest Assured

Rest Assured is a Java developer’s dream: clean, expressive, and great for asserting REST API behavior right in your test suite. You won’t get a GUI or fancy reports, but that’s not the point — it’s built for precision, not presentation. If your stack is Java-centric and you want unit-test-grade control over your API contracts, this is a solid fit.

Benefits

• Rest Assured has a fluent Java DSL for expressive test syntax, and more generally has native support for JSON/XML validation.
• It also offers easy integration with JUnit, TestNG, and CI pipelines, making it a great fit for developers already using Java.

Drawbacks

• Rest Assured is Java-only, making it unsuitable for teams using other languages.
• It also lacks meaningful native GUI systems or test analytics features, requiring third-party solutions if teams need that feature.

6. Karate DSL

Karate DSL combines API testing, performance testing, and mocking into one sleek package. It’s got an opinionated feel, but that’s part of its charm — tests are concise, readable, and easy to parallelize. You get a lot out of the box without bolting on external tools, which is why it’s pretty attractive for smaller teams that need generalized testing. Debugging can be a bit opaque at times, but for cross-functional teams embracing Gherkin, Karate feels like a great middle ground.

Benefits

• Karate DSL presents a unified framework for API, UI, and performance testing.
• The use of Gherkin for its syntax lowers the entry barrier significantly, making a lower learning curve.
• Karate DLS supports parallel execution out of the box, and has built-in mocking and data-driven testing, allowing for rapid and easy-to-launch testing programs.

Drawbacks

• Debugging is difficult for non-developers due to some idiosyncrasies in the implementation.
• DSL may be less flexible for edge-case logic.
• Karate DSL has a smaller community than Postman or Rest Assured, which can be a limiting factor for continued growth and iteration.

7. Sauce Labs

One of the most popular testing frameworks of yesteryear — API Fortress — has now fully merged with Sauce Labs. Sauce Labs is more than just a testing tool — it’s a governance layer, a monitoring engine, a security system, and a CI/CD automation platform. While Sauce Labs was always a good offering for performance metrics and insights generation, the union of it and API Fortress makes for a solid offering with a wide range of solutions.

Benefits

• This tool is an enterprise-grade platform with governance in mind, making it a good fit for larger teams with enterprise goals.
• It supports visual and code-based test creation, opening the testing process to more teams.
• Additionally, it has pretty deep monitoring and alerting features, which can be helpful for teams building from the ground floor.

Drawbacks

• Sauce Labs is a premium product with premium pricing, which may deter small teams.
• The merger of Sauce Labs and API Fortress has introduced some complexity. For those who knew either tool in isolation, you now need to relearn how to use the unified tool, which can add complexity.

8. Tricentis Tosca

Tricentis Tosca is a leading enterprise platform for companies that need a comprehensive test suite solution. It’s built around model-based automation, so it doesn’t rely on testers implementing their own code — instead, it offers comprehensive testing through a variety of ready-to-deploy test suites. Tosca is best when scaled across complex organizations that need traceability, risk-based testing, and deep integration into their toolchains, but this is its main drawback — it’s big, it’s expensive, and not for everyone.

Benefits

• Tosca’s model-based test automation reduces scripting burden, allowing for quicker iteration and deployment.
• This tool scales well for complex enterprise environments, allowing teams to be pretty flexible with how and what they deploy.
• Comprehensive reporting and traceability make for better visibility and monitoring across the board.

Drawbacks

• While it’s a powerful tool, that power comes with a high cost and a lot of proprietary tooling
• Tosca has a pretty steep learning curve, and that can ultimately generate significant vendor lock-in.
• This solution can be overkill for lightweight or startup-scale projects.

9. Assertible

Assertible is refreshingly simple, designed for post-deployment API checks and uptime monitoring. That being said, it’s not a solution for heavyweight test orchestration or more complex testing suites. If you want quick wins with little overhead — for instance, triggering tests after every GitHub push and getting Slack alerts when things break — it’s a fantastic solution. Beyond that, it offers little in the way of replacing your more comprehensive testing solutions.

Benefits

• Assertible has a relatively simple setup process, allowing teams to get going quicker with less overhead.
• It also has decently easy integration processes for GitHub, Slack, and CI/CD pipelines, allowing this setup to be pervasive throughout your dev stack.
• Assertible has a quick import feature from Postman, allowing teams to pivot quickly.

Drawbacks

• While it’s relatively easy to get started, more complex test logic has relatively limited support.
• There’s no real deep performance or security testing on offer here, which means you’re limited to a very specific type and function of testing.
• The lack of significant scripting or broad protocol support further narrows this focus.

10. ACCELQ

ACCELQ is a compelling testing solution based around AI, and while the inclusion of AI is a dime a dozen in 2025, the way ACCELQ uses it is unique. In essence, AI is used at scale to offer a multimodal and multi-channel automated system. Instead of just plugging in a singular solution or framework, you can use ACCELQ as a unified agentic platform to handle your testing, iteration, and quality management, all within a no-code environment built for the enterprise.

Benefits

• Highly modular and multimodal, making it an excellent fit for a variety of use cases and code types.
• Zero code makes it a strong solution for teams needing highly flexible and collaborative tooling.

Drawbacks

• ACCELQ is a relative newcomer, and it comes with a bit of a learning curve to really use the tools to their full extent. This is a case of being exceptionally easy to get started while being difficult to fully leverage.

API Testing Will Continue to Evolve

These ten tools represent the top of the current market, but this list is absolutely subject to change. This transitory nature reveals a bit about the industry as a whole: testing, just like APIs, is a constantly evolving area, and what might be your best bet today might change tomorrow, next week, or next year.

The reality is that the codebases of yesteryear with their monolithic structures aren’t as common in 2025, and the rise of agentic development could make the code of today obsolete. This means that test service providers need to be quick — and notably, those who adopt new solutions are likely to stay at the top of the game while those who don’t are likely to be knocked down by newcomers who are more agile, more adaptive, and more aligned with modern development.

Accordingly, consider this list a good starting guide, but evaluate your solutions based on your codebase, your development direction, and your overall needs.