Microsoft has informed administrators of its Microsoft 365 platform that the Internet Explorer (IE) mode in Edge will remain supported until the end of 2029. This notice, identified as MC1473151, is aimed at companies still using legacy software that relies on this feature. Internet Explorer 11 (IE11), the last version of Microsoft’s older browser, was officially removed from personal computers in 2022. However, its underlying rendering engine, called Trident, still operates in the background within Edge, allowing certain legacy web applications to function without modification. The Internet Explorer mode in Edge does not actually launch the old browser itself. Instead, it temporarily switches Edge—normally based on the Chromium open-source project—to use the Trident engine, also known as MSHTML. This allows specific websites, selected by an administrator from a list called the Enterprise Mode Site List, to be displayed using the older engine. Trident, currently at version 7.0, supports outdated technologies like WebGL applets and the now-obsolete SPDY protocol. This means that older intranet applications, such as those created using Microsoft FrontPage, can continue to run without requiring code changes. Microsoft’s message, published recently, reaffirms a commitment made in 2021 to support the IE mode at least until the end of 2029 across various environments, including Worldwide, GCC, GCC High, and DoD. The company promises to provide at least one year’s notice before any removal date. For companies not using this feature, no action is required. However, for those that are, a gradual migration plan is needed. This involves identifying which websites and applications still rely on IE mode and deciding whether to update, replace, or rebuild them using modern web technologies. Microsoft also offers the App Assure program, a free service that helps customers address compatibility issues with Edge or the IE mode. While the continued support of IE mode provides a temporary solution for legacy systems, it also carries security risks. Unlike modern browsers from Google and Mozilla, which use AI-driven security tools and release hundreds of patches every 15 days, the Trident engine used by IE mode remains vulnerable. Earlier this year, Microsoft had to revise the activation shortcuts for IE mode after discovering that hackers were exploiting them to gain access to computers. With at least two more years of support ahead, companies are encouraged to plan for a transition to more secure and up-to-date technologies.