Selenium is a purely open-source and portable automation testing tool.
It supports different languages such as C#, PHP, Java, Perl, Python, JS, and Groovy.
It also supports different OS, including Windows, Linux, UNIX, and Mac OS.
It provides powerful methods such as Xpath, DOM, and CSS to locate elements.
Since it is an open-source tool, developers can customize the code. Also, the developer community is supported by Google.