What Is SoapUI and What Is It Used For?
SoapUI is an automated testing tool for SOAP and REST APIs, positioned on its own site as "the world's most widely-used" API testing tool. It is used to write, run, integrate, and automate API tests, and it comes in two forms: a free open-source edition (SoapUI Open Source) and a more advanced commercial edition (ReadyAPI). If you need to verify that an API returns correct results, handles load, or stays secure, SoapUI is the entry point for the functional testing fundamentals, while ReadyAPI covers the advanced cases.
What SoapUI actually does
At its core, SoapUI sends requests to an API and checks the responses. That single loop covers a lot of ground:
- Writing tests — you define a request (endpoint, method, headers, body) and the assertions that decide whether the response is correct.
- Running tests — execute a single request or a whole suite, manually or as part of a pipeline.
- Integrating tests — connect API tests into CI/CD so they run automatically on every build.
- Automating tests — use property transfers, custom scripting, and data-driven inputs so tests don't need manual editing each run.
The site frames this as improving "the efficiency of your testing strategy as a whole," which is the practical reason teams adopt it: API-level tests run faster and catch problems earlier than GUI-level tests.
Open source vs. ReadyAPI: what you get
The site presents a direct comparison. The open-source edition is for getting started with the fundamentals; ReadyAPI is for advanced testing. Here is how the two line up on the dimensions the site lists:
| Capability | ReadyAPI | SoapUI Open Source |
|---|---|---|
| Multi-protocol support | REST, SOAP, GraphQL, Apache Kafka, gRPC | REST, SOAP |
| Automation | Basic property transfer, custom scripting, CI/CD integrations, data generation, dynamic data sources, assertion groups | Basic |
| Collaboration | Jira, Slack, GitHub, Bitbucket, GitLab | — |
| Definitions | WSDL, OpenAPI, AsyncAPI, Apache Avro, Swagger, Protobuf | — |
| Testing | Functional, security, performance, service virtualization & mocking | Basic functional testing, basic performance testing |
Read this as a scope decision, not a quality ranking. If your work is REST or SOAP functional testing and you want a no-cost starting point, SoapUI Open Source matches the need. If you need GraphQL, Kafka, or gRPC coverage, security or load testing, service virtualization, or team collaboration hooks into Jira and Git, those appear only on the ReadyAPI side.
Where it fits in an API testing practice
The site groups API testing into several concept areas, and SoapUI is the tool that touches most of them:
- Functional testing — confirming the API "functions as intended, every time."
- Performance testing — load-testing virtual users against the API to see how it holds up.
- Security testing — checking third-party, public, and internal APIs for vulnerabilities.
- API mocking / virtualization — standing in for an API that isn't built or available yet, to save time and resources.
- Data-driven testing — feeding varied inputs to increase coverage without writing each case by hand.
- Test reporting — collecting metrics and statistics to measure whether testing is working.
SoapUI Open Source covers the functional and basic performance layers; the remaining areas are where ReadyAPI is positioned.
How to decide if it's the right tool
Work through these questions in order:
- What protocols do you test? REST and SOAP only → SoapUI Open Source is sufficient. GraphQL, Kafka, or gRPC in the mix → you need ReadyAPI.
- Do you need security, load, or virtualization testing? If yes, those are listed under ReadyAPI, not the open-source edition.
- Does your team need shared collaboration? Integrations with Jira, Slack, GitHub, Bitbucket, and GitLab appear only in the ReadyAPI column.
- Are you just starting out? The site's own framing is to "download SoapUI to get started with the fundamentals" and move to ReadyAPI for advanced testing.
One caveat worth stating plainly: the source material does not list prices for either edition, so treat ReadyAPI as a commercial product to evaluate directly rather than assuming any cost structure. Likewise, the open-source edition is described as open source, but the page does not spell out license terms — check those before adopting it in a commercial setting.
The short answer
SoapUI is a tool for testing APIs by sending requests and validating responses, used to write, run, integrate, and automate tests for SOAP and REST services. Its open-source edition covers functional and basic performance testing; ReadyAPI extends the same family to GraphQL, Kafka, gRPC, security, load, virtualization, and team collaboration. Choose based on your protocols and whether you need the advanced testing types — that single question usually settles it.