API automation testing tools (2026 list)
A practical list of API automation testing tools, from code-free test generation to code-first frameworks. Each entry covers what the tool does, who it suits, and where it falls short, so you can pick the right one for your stack.
Quick comparison
| Tool | Type | Open source | Best for |
|---|---|---|---|
| Keploy | Traffic-based test and mock generation | Yes | Auto-generating API tests without writing code |
| Postman | API client with test scripts | No | Manual exploration plus scripted checks |
| Rest Assured | Java library | Yes | Java teams writing tests in code |
| Karate | DSL-based framework | Yes | Readable API tests without heavy coding |
| Playwright | Browser and API testing framework | Yes | Teams already using Playwright for UI tests |
| SoapUI / ReadyAPI | Functional API testing suite | SoapUI yes, ReadyAPI no | SOAP and enterprise REST testing |
| Schemathesis | Property-based testing from OpenAPI | Yes | Finding edge-case bugs from a spec |
1. Keploy
Website: https://keploy.io
GitHub: https://github.com/keploy/keploy
Keploy is an open-source API testing platform that records real API traffic and turns it into test cases and data mocks automatically. It uses eBPF to capture calls at the network layer, so it works without code changes or an SDK in your application.
Why teams use it
- Generates tests from real traffic instead of hand-written scripts
- Mocks databases and downstream services, so tests run without live dependencies
- Test cases are stored as YAML files you can commit to Git and run in CI
Getting started
curl --silent -O -L https://keploy.io/install.sh && source install.sh
keploy record -c "go run main.go"
keploy test -c "go run main.go" --delay 10
Limitations: runs natively on Linux; macOS and Windows need Docker or WSL.
2. Postman
Website: https://www.postman.com
Postman is a widely used API client that supports test scripts in JavaScript, collections, and runs in CI through Newman or the Postman CLI. It is strong for manual exploration and team collaboration.
Limitations: tests are written and maintained by hand, and many collaboration features need a cloud account. See a detailed comparison here: Keploy vs Postman.
3. Rest Assured
Website: https://rest-assured.io
Rest Assured is a Java library for testing REST APIs with a fluent, readable syntax. It plugs into JUnit or TestNG and fits naturally into Maven or Gradle builds.
Limitations: Java only, and every test is written in code.
4. Karate
Website: https://www.karatelabs.io
Karate lets you write API tests in a Gherkin-style syntax without step definitions. It also covers mocks, performance testing through Gatling, and UI automation.
Limitations: the DSL has a learning curve, and complex logic can get awkward compared to plain code.
5. Playwright
Website: https://playwright.dev
Playwright is best known for browser testing, but its request API makes it a good fit for API tests too, especially when you want UI and API checks in one suite.
Limitations: API testing is a secondary feature, so there is less tooling around it than in dedicated API tools.
6. SoapUI and ReadyAPI
Website: https://www.soapui.org
SoapUI is an open-source tool for functional testing of SOAP and REST APIs. ReadyAPI is the commercial version with data-driven testing, virtualization, and reporting.
Limitations: the interface feels dated, and advanced features are paid.
7. Schemathesis
Website: https://schemathesis.io
Schemathesis reads your OpenAPI or GraphQL schema and generates many test inputs automatically to find crashes and spec violations.
Limitations: it depends on an accurate schema and checks spec conformance rather than business logic.
How to choose an API automation testing tool
- Want tests without writing them: Keploy
- Java codebase: Rest Assured
- Readable tests for mixed-skill teams: Karate
- Already using Playwright for UI: Playwright
- Spec-driven edge-case testing: Schemathesis
FAQ
What is API automation testing?
It is the practice of running API tests automatically, usually in CI, to check that endpoints return the right responses, status codes, and data after every change.
Which API automation testing tool is best for beginners?
Keploy is easy to start with because it creates tests from real traffic, so you do not need to write test scripts first. Postman is also beginner-friendly for manual testing.
Can I automate API tests without writing code?
Yes. Keploy records API calls while you use your app and replays them as tests, with dependencies mocked automatically.
Are there free open-source API testing tools?
Yes. Keploy, Rest Assured, Karate, Playwright, SoapUI, and Schemathesis are all open source.
Get started
Try automated API test generation: Keploy API testing