Google Analytics counts IE (Internet Explorer) browsers based on the user-agent string that is sent by the browser to the website. When a user visits a website with Google Analytics tracking code implemented, the tracking code captures the user-agent string, which contains information about the browser and the operating system being used.
For Internet Explorer browsers, the user-agent string typically includes specific information such as "MSIE" followed by the version number. Google Analytics identifies this information and categorizes the visitor as an IE browser user. The version number is used to determine the specific version of IE being used.
Google Analytics then aggregates these browser-specific data to provide insights on the usage patterns, demographics, behavior, and other relevant data for IE users. This information can be used by website owners to optimize their site's performance and user experience.