There are several reasons to use Selenium over other test automation tools out there:
It is the right tool for the right job
It is free of cost
It is open source
It is highly flexible
Selenium is a great tool for testing web applications and interacting with the application like a real user would. It uses a real browser to click, type, and fill out forms. It is as close to a human user as you can get. It's the perfect tool for testing the flow of the web application from start to finish.
Nothing can beat the free price tag! While there are other commercial products that have more advanced features available for purchase, they tend to run into tens of thousands of dollars per license. Selenium is so cheap that you will be able to finish this book and build a whole test suite without spending another dollar.
Tip
As old anti-proverb states: there is no free lunch, but there is always more cheese in the mousetrap. A free tool does not mean that the tests will write themselves for free; there will always be expenditure on someone's time. By following good practices, we will not be able to eliminate this cost but will try to reduce it as much as possible in the long run.
Selenium is Open source software (OSS), but this means more than "it is free". As with other OSS, with Selenium, you don't just get the product but you get a whole community; you become part of the family. The majority of Selenium developers cannot wait to help someone who is in need, or to share some really great workaround for a difficult problem they ran into. This sure beats paying for expensive and underwhelming technical support you get with a commercial product.
Selenium is incredibly flexible; because it is Java-based, you can run it on most operating systems or browsers. You can even use it to test iOS and Android browsers. On top of that, you can run it in "headless mode" with an emulation browser, or set up a grid to increase your capacity, but we will cover more on these topics later in the book.