What is the MSIE browser?

 MSIE is a common abbreviation for Microsoft Internet Explorer, a retired web browser that was developed and bundled with the Microsoft Windows operating system. It was often referred to simply as IE.

While Internet Explorer is no longer actively supported, its legacy is still present in web development. MSIE is a key component of the browser's "user agent" string, which is a piece of text sent to a website to identify the browser, operating system, and other information. This string often contained the letters "MSIE" to identify the browser. For example, a user agent string might look like this: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1). This string was used by developers to serve specific content tailored to IE's unique rendering engine.

Microsoft has since replaced Internet Explorer with Microsoft Edge, a modern browser with better performance and support for current web standards. Edge includes an "IE mode" feature that allows users to open websites in an Internet Explorer-compatible environment, which is particularly useful for corporate or government websites that were built specifically for the older browser.