Google Analytics

Google Analytics is the world's leading analytics platform for web and application tracking. With Google Analytics, website and application owners can track user behaviour across their sites or applications, free of charge. Google Analytics provides valuable insight, like how long a visitor stays on page, what country it is from, what type of device it is using, and what links and pages the user it is interacting with. This data can then be used by domain owners and developers to improve content, navigation and structure of site to ultimately provide a better experience for the end user.

Google Analytics provides a free service that is monetized with data.