12 Best API Testing Tools to Power Your QA in 2025
APIs are the backbone of modern software — from cloud services and microservices to mobile apps and third-party integrations. Choosing the right testing tools helps teams keep APIs secure, performant, and reliable as architecture complexity grows.
Why API testing matters in 2025
API testing verifies contract, performance, security, and compatibility across environments. With adoption of GraphQL, gRPC, and event-driven systems, teams need versatile tooling that integrates into CI/CD, supports collaboration, and scales with test suites.
1. Postman — the universal workhorse
Overview: Postman is widely adopted for exploratory testing, collaboration, and automated test runs. It supports REST, SOAP, and GraphQL and is backed by a large ecosystem.
Key features:
- Workspaces and team collaboration
- Automated test scripts via Newman
- Mock servers, monitoring, and reporting
- CI/CD integrations
Strengths: Beginner-friendly UI, strong community, extensive docs. Drawbacks: Can be resource-heavy at scale, and advanced features are often behind paid tiers.
2. SoapUI — mature and feature-rich
Overview: SoapUI (and its ReadyAPI commercial suite) is built for thorough testing of REST and SOAP APIs, including security and load scenarios.
Key features:
- Functional, security, and performance testing
- Drag-and-drop test creation and data-driven tests
- CI/CD support
Strengths: Robust for complex flows and enterprise needs. Drawbacks: Steeper learning curve and paid enterprise features.
3. Katalon Studio — hybrid code/no-code automation
Overview: Katalon combines script and codeless approaches across API, web, mobile, and desktop testing and fits well into CI/CD pipelines.
Key features:
- IDE with autocompletion and dual script/manual modes
- BDD/Gherkin support and built-in integrations
Strengths: Scalable for automation teams with both free and paid plans. Drawbacks: Some stability issues on Linux and limited integrations with certain PM tools.
4. Insomnia — clean client with GraphQL focus
Overview: Insomnia is an open-source API client praised for a sleek UI, strong GraphQL support, and environment management.
Key features:
- Authentication and environment variable management
- Plugin extensibility and response validation
Strengths: Excellent for request management and GraphQL. Drawbacks: Collaboration and load testing features are limited to paid versions.
5. Rest-Assured — fluent Java testing library
Overview: Rest-Assured is a Java library ideal for automating REST validations inside Java projects and CI/CD pipelines.
Key features:
- JSON and XML support with fluent assertion syntax
- Easy integration with Java test frameworks
Strengths: Free, extensible, perfect for Java teams. Drawbacks: Requires Java knowledge and lacks a visual UI.
6. Karate DSL — readable, declarative tests
Overview: Karate combines API testing, UI automation, and performance tests using a readable DSL that lowers coding overhead.
Key features:
- Data-driven testing and built-in auth support
- Multipart uploads and CI/CD friendliness
Strengths: Minimal coding required and active community. Drawbacks: Java-based and fewer advanced reporting UI features.
7. ACCELQ — codeless end-to-end coverage
Overview: ACCELQ focuses on codeless API and UI test automation with features aimed at business process validation.
Key features:
- API chaining and regression automation
- Integrated CI workflows and dynamic reporting
Strengths: Streamlines business-process testing and offers cloud-based security. Drawbacks: Limited flexibility outside the ACCELQ ecosystem.
8. JMeter — the performance and load standard
Overview: JMeter is an open-source staple for load and performance testing across many protocols, including HTTP and SOAP.
Key features:
- GUI and CLI modes, large plugin ecosystem
- Functional and performance testing capabilities
Strengths: Free, scalable, versatile. Drawbacks: Learning curve and primarily performance-focused rather than functional-test centric.
9. BlazeMeter — cloud-scale load testing
Overview: BlazeMeter provides cloud-based load testing with real-world scale, analytics, and CI/CD integrations.
Key features:
- Real-time analytics and global endpoint monitoring
- Support for JMeter scripts and data-driven tests
Strengths: Enterprise-grade scaling and collaboration. Drawbacks: Pricing can be steep for smaller teams.
10. Apigee — enterprise API lifecycle management
Overview: Apigee, from Google, covers API design, analytics, security, and testing across the API lifecycle.
Key features:
- Contract testing, performance analytics, and a developer portal
- Built-in monitoring and management
Strengths: Robust for enterprise needs. Drawbacks: Complexity and enterprise pricing may not suit small projects.
11. Testsigma — AI-assisted codeless testing
Overview: Testsigma emphasizes AI and codeless automation across web, mobile, and API testing with quick onboarding.
Key features:
- Real-time validation, data-driven tests, and CI/CD integration
- Chained API testing
Strengths: Accessible to non-developers and feature-rich. Drawbacks: Advanced capabilities require subscription.
12. mabl — AI-driven low-code testing
Overview: mabl offers AI-powered test generation and unified API/UI testing with features like Postman import.
Key features:
- Unlimited parallel runs, data-driven tests, and unified reporting
Strengths: Enables non-technical users to build robust tests quickly. Drawbacks: Focused on web and cloud environments.
Key trends shaping API testing
- Codeless automation and AI-assisted test generation reduce the barrier for non-developers.
- Tight CI/CD integrations are standard, enabling faster feedback loops.
- Collaboration-first workflows let large teams share test assets and environments.
- Growing support for GraphQL, gRPC, and WebSockets as API architectures diversify.
Evaluate tools based on protocol support, team skill set, CI/CD integration, scalability, and cost. A mix of open-source libraries for developers and codeless/AI platforms for broader teams often provides the best balance for future-proof API QA.