Microsoft Set an End Date for the Last Piece of Internet Explorer
On September 23, 2026, ghacks reported that Microsoft sent a formal notice through the Microsoft 365 admin center confirming that IE Mode in Microsoft Edge will be retired by the end of 2029. That’s the last remaining way to run the Internet Explorer engine on modern Windows. After that date, it’s gone.
If your business uses any internal web apps, vendor portals, or line-of-business tools that only work in Internet Explorer, this deadline is your problem. Not someday, now. Microsoft said explicitly that some modernization projects take several years, which is exactly why they’re sending the reminder three-plus years in advance.
What IE Mode Actually Is
IE Mode is a compatibility feature built into recent versions of Edge. It lets specific pages or apps render using the old Internet Explorer 11 engine, technically called the Trident engine or MSHTML, instead of the modern Chromium engine that Edge normally uses. It was Microsoft’s way of keeping legacy apps alive while pushing organizations off the actual Internet Explorer 11 browser, which was retired years ago.
The message Microsoft sent through the admin center, referenced as MC1473151, isn’t new policy. Microsoft first announced this plan back in 2021. What changed on September 23, 2026 is that they’re restating it and pushing organizations to act. They’ve also committed to publishing a new end-of-support notice at least one year before the actual cutoff date.
Who Actually Needs to Worry About This
If your business doesn’t use any IE-dependent apps, you don’t need to do anything. Microsoft said so directly. But if you’re running anything that requires IE Mode to function, you should start an inventory now. Common culprits include older ERP systems, custom-built internal portals from the mid-2000s through early 2010s, manufacturing or logistics tools, and some government or healthcare vendor portals that were never modernized.
The practical issue is that rewriting or replacing a legacy web app isn’t a weekend project. Depending on what it does and who built it, a migration can take anywhere from a few months to a couple of years. Waiting until 2028 or 2029 puts you in a bad position if something goes wrong.
What to Do Between Now and 2029
Microsoft’s own guidance breaks it into two steps: find out what you have, then fix it. That sounds simple, but the first step trips up a lot of organizations because IE-dependent apps are often undocumented or quietly maintained by someone who’s no longer at the company.
- Audit your internal and vendor apps for any IE Mode dependencies, using Edge’s IE compatibility list or by checking with your IT team or MSP.
- Contact vendors for any third-party tools that require IE Mode and ask directly about their modernization roadmap.
- For custom-built apps, evaluate whether they can be rebuilt in a modern framework or replaced entirely.
- Check whether Microsoft’s App Assure service applies to you. It’s available to eligible customers and can help assess compatibility with newer platforms.
This is also a good time to look at your broader Windows environment. If you’re still running older versions of Windows or haven’t fully moved to Microsoft 365, those issues compound each other. The Windows 10 and Microsoft 365 support changes are already forcing upgrade decisions for a lot of businesses, and IE Mode retirement adds another layer to that planning.
If you’re already thinking about where Windows fits in your infrastructure over the next few years, the Windows 11 24H2 end of support timeline is worth understanding alongside this. These deadlines tend to stack up, and it’s easier to plan them together than react to each one separately.
The concrete takeaway: check your apps now, document what uses IE Mode, and build a realistic migration timeline before 2027. Three years sounds like a lot until a vendor tells you their replacement product won’t be ready until late 2028. If you want help doing that audit or figuring out what a migration actually involves, book an IT assessment and we can work through it with you.
FAQ
When exactly is Microsoft retiring IE Mode in Edge?
Microsoft has confirmed support ends by the end of 2029. They will issue a separate end-of-support notice at least one year before the final date. The retirement was first announced in 2021 and restated through admin center message MC1473151 on September 23, 2026.
Do I need to do anything if my business doesn’t use Internet Explorer?
No. Microsoft stated clearly that organizations with no IE-based apps or applets don’t need to take any action. The retirement only affects businesses that currently use IE Mode in Edge to run legacy applications or websites that won’t work in a modern browser.
What happens to IE Mode apps after 2029?
Microsoft hasn’t confirmed that apps will break immediately, but IE Mode will no longer be supported or maintained. Security vulnerabilities won’t be patched, and compatibility with future Windows updates won’t be guaranteed. Running unsupported browser technology in a business environment is a real security risk.
How long does it take to migrate a legacy IE app?
It varies widely. Simple sites might take weeks. Custom-built internal tools or third-party apps that require vendor cooperation can take one to two years or longer. Microsoft cited this timeline problem directly as the reason for issuing the 2029 reminder now, in 2026.
