Microsoft Sets 2029 Deadline to End Internet Explorer Mode

REDMOND, Wash. — Microsoft is preparing to permanently retire Internet Explorer Mode in its Edge browser by the end of 2029, ending support for the 30-year-old MSHTML rendering engine. Enterprise IT departments have been warned to overhaul legacy corporate web applications before the shutdown.

The warning appeared in a Microsoft 365 admin center notification identified by reference code MC1473151. Microsoft said Internet Explorer Mode inside Microsoft Edge will remain supported until at least late 2029 and promised to issue a formal final-retirement notice at least 12 months before the complete shutdown.

Companies that do not use legacy IE-dependent applets or proprietary internal tools will not need to make operational changes after the advisory. Microsoft said organizations running critical infrastructure on legacy code should begin assessing software risks early and remove dependencies before the MSHTML engine is permanently decoupled from Windows.

Internet Explorer Mode was integrated into Microsoft Edge after the browser was rebuilt on Google’s open-source Chromium engine in January 2020. It lets employees open legacy web pages and internal portals within a modern browser interface. When an approved legacy address is accessed, Edge invokes the Windows Trident layout engine, technically maintained as MSHTML.dll, to render content according to Internet Explorer 11 standards.

The dual-engine arrangement maintains support for MSHTML 7.0. It also allows organizations to run legacy WebGL applets, custom ActiveX controls, VBScript, and retired networking protocols such as SPDY without keeping a separate browser installation.

Many customized enterprise resource planning (ERP) platforms, human resources portals, government services, and industrial control interfaces created in the late 1990s and 2000s still depend on MSHTML-specific code. Replacing or rebuilding that line-of-business software can require multi-year planning cycles, software rewrites, vendor procurement, and extensive compatibility testing.

Microsoft is offering technical assistance through its FastTrack App Assure program, which helps enterprise clients resolve custom application compatibility problems on modern Windows 11 and Microsoft Edge deployments. The standalone Internet Explorer 11 desktop application, meanwhile, was officially retired on June 15, 2022, and permanently disabled across modern Windows platforms through a February 14, 2023, software update.

The technology being phased out dates to the early commercial internet. Microsoft released Internet Explorer 1.0 in August 1995 as part of the Internet Jumpstart Kit for Windows 95, using code licensed from Spyglass Mosaic. The company introduced its proprietary Trident engine in October 1997 with Internet Explorer 4.0.

Internet Explorer reached roughly 95 percent of worldwide browser market share by 2002 after the “First Browser War” with Netscape Navigator. Trident-based features and proprietary extensions, including ActiveX controls and Browser Helper Objects (BHOs), consequently became standard building blocks for internal corporate web tools.

Microsoft launched Internet Explorer 11 in October 2013 alongside Windows 8.1 and later introduced a new rendering platform with Microsoft Edge in 2015. Even so, thousands of institutional systems remained tied to MSHTML architecture.