Appium and Selenium share the same WebDriver protocol but serve different purposes. Selenium automates web browsers, while Appium automates mobile applications (both native and hybrid). Appium’s advantage lies in its cross-platform compatibility, allowing the same test scripts to run on Android and iOS. In contrast, Selenium focuses solely on web automation. Appium also supports a no-recompilation policy, meaning apps don’t need modification for testing. However, Selenium is lighter and easier for beginners. Testers in New York often use both — Selenium for web and Appium for mobile — to achieve a complete automation strategy across digital products.