Microsoft says IE 11 support for Teams will end on Nov. 30, 365 apps on Aug. 17, 2021; legacy Edge browser will not receive security updates after March 9, 2021
Microsoft will begin the gradual phase-out of IE11 by ending Teams support for it this fall.
Context & Ripple Effects
This is the second act of a retirement Microsoft has been staging for years: after cutting off IE8, IE9, and IE10 back in January 2016, the company is now putting dates on IE11 itself — Teams first (Nov. 30), then Microsoft 365 apps (Aug. 17, 2021), while legacy Edge loses security updates even sooner, on March 9, 2021. The sequencing matters: by pulling its own flagship collaboration and productivity apps off IE11 first, Microsoft forces enterprise migration before any formal end-of-life announcement.
First-order effects
- Enterprises still standardizing on IE11 for internal web apps must move Teams users to another browser within months or lose access to the app entirely.
- Organizations running legacy Edge lose their security-update safety net on March 9, 2021 — earlier than either IE11 deadline — pushing them onto Chromium-based Edge.
Second-order effects
- IT departments that built line-of-business tools against IE-only technologies face forced remediation budgets, accelerating demand for web-app modernization work ahead of the Aug. 17, 2021 cutoff.
- The staged deadlines give Microsoft leverage to push holdout customers toward Chromium-based Edge, consolidating its browser base around the new engine before the broader exit.
Third-order effects
- The pattern holds through what followed: Microsoft went on to announce IE's full retirement for June 15, 2022 and later disabled the desktop app outright, and the same staged-cutoff playbook reappears in Edge's Manifest V2 extension phase-out and the end of Microsoft 365 app support on Windows 10 — an industry structure where platform owners, not standards bodies, set de facto browser lifecycles.
The trend: Microsoft is executing a staged, app-by-app decommissioning of legacy browsers, using its own product suite as the forcing function to migrate enterprises onto Chromium-based Edge.