Selenium is a portable software-testing framework for web applications. Selenium provides a record/playback tool for authoring tests without the need to learn a test scripting language (Selenium IDE). Developed by SeleniumHQ
License: Open Source
Selenium is a powerful, versatile tool that supports multiple browsers and programming languages, making it suitable for complex testing scenarios. In contrast, CasperJS is lightweight and JavaScript-based, making it easier for developers to use for simpler tasks but lacking the extensive features and browser support of Selenium.