As illustrated in All You Need To Know About UI Testing, Selenium is the best way to go for automated UI testing. A great learning curve helps you run the Selenium tests quickly and easily. To have hassle-free testing, you can use an online cross-browser testing platform that integrates with Selenium and can provide many features through drag and drop functionality.
There are a few good tools available online as well:
LambdaTest: Offers a cross-browser testing cloud, to help you test your website across 2000+ real browsers for both desktop & mobile. You can even automate browser testing using its online Selenium Grid and have a developer-friendly browser that is designed to fasten your responsive testing.
Katalon Studio: Selenium requires extensive coding knowledge and testing expertise. To shorten that learning curve, you can try Katalon Studio for codeless automation. Katalon allows teams at any level to transform into automation testing quickly and easily.