Selenium is an open-source umbrella project for automating web browsers. Its core, WebDriver, implements the W3C WebDriver specification, so the same instructions run in many browsers. Selenium IDE is a browser extension that records and plays back user actions, and Selenium Grid runs tests in parallel across multiple machines. Language bindings are available for Java, Python, C#, Ruby, JavaScript and Kotlin. Selenium is a set of libraries and tools that teams install and run themselves, in a test environment or CI pipeline, and many other testing tools build on it.
The project is a member of the Software Freedom Conservancy, a US 501(c)(3) non-profit, which avoids the need for a separate legal entity. The source code is on GitHub under the Apache 2.0 licence. Selenium has no hosted service of its own, so test data stays in the environment where you run it. For European organisations, the dependency lies with the community project and its US non-profit home rather than with a commercial supplier, and the licence permits self-hosting, forking and long-term use.