Selenium - Selenium automates browsers. That's it! What you do with that power is entirely up to you. Primarily, it is for automating web applications for testing purposes, but is certainly not limited to just that.
BrowserStack - BrowserStack is a software testing platform for developers to comprehensively test websites and mobile applications for quality.
UI.Vision - Modern open-source task and test automation tool and Selenium IDE.
LambdaTest - Perform Web Testing on 2000+ Browsers & OS
TestComplete - TestComplete Desktop, Web, and Mobile helps you create repeatable and accurate automated tests across multiple devices, platforms, and environments easily and quickly.
CodePen - A front end web development playground.