When Windows 10 ships this summer, it will include a new default web browser: Microsoft Edge. The new browser replaces its predecessor, Internet Explorer, with a completely revamped user interface and rendering engine. The Edge browser (still labeled with its codename, Project Spartan, and still far from finished) is available today in preview releases of Windows 10, as shown in Figure A.
That doesn’t look much like Internet Explorer, does it? Nor does it work much like Internet Explorer.
In Windows 10, Internet Explorer 11 will still be available, primarily for business customers who need its feature set for compatibility with old line-of-business apps. But it won’t be the default.
The Edge browser is likely to be significantly faster than its predecessor, and it is designed to work better with the modern web. If you’re planning a Windows 10 migration for your enterprise network, though, you’ll probably go out of your way to change the default browser back to Internet Explorer 11.
To understand why, we have to look at the part of the browser you can’t see.
Trident vs. EdgeHTML
The biggest difference between the old browser and the new is the underlying rendering engine, the code that retrieves web pages from the internet and translates HTML, XML, and other markup into the text, pictures, and layout the designer intended.
For nearly 20 years, Internet Explorer has used the Trident rendering engine (Mshtml.dll), which sets it apart from its competitors (Firefox with Gecko, Safari with Webkit, and Chrome with Blink, a forked version of Webkit).
Through the years, Microsoft has developed Trident with the goal of maintaining compatibility with old web pages. That has resulted in an unbelievably complex document model. Web designers can add code to page headers to help Internet Explorer handle the different modes. You can test those document modes using the F12 tools in Internet Explorer, as shown in Figure B.
In theory, that’s an elegant way to solve the problem of old web pages designed for a bygone era. In practice, it’s just a mess, and it’s a major reason why Microsoft has struggled to keep Internet Explorer relevant.
The most important goal of EdgeHTML is interoperability, starting with support for modern web standards. The idea is to design the rendering engine so that it works with the pages people are likely to see today, in the process helping web-page designers avoid cross-browser inconsistencies.
In Windows 10, Microsoft Edge will use only the new rendering engine. Internet Explorer 11 and the Trident engine will still be available, primarily for business customers who need its feature set for compatibility with old line-of-business apps. But it won’t be the default. And although Trident will still receive security fixes, it won’t be updated to include support for new web standards.
If you’re planning a Windows 10 migration for your enterprise network, you’ll probably go out of your way to change the default browser back to Internet Explorer 11. When you do that, you’ll be able to deploy a single browser across all your supported Windows versions, including Windows 7, Windows 8.1, and Windows 10.
On your enterprise network, you’ll have a single tool you can use to manage internal and external web pages that have compatibility issues. Use Group Policy to turn on Enterprise Mode, and you’ll be able to instruct Internet Explorer 11 to render a site using Internet Explorer 8 or Internet Explorer 7 settings. For details, see the Microsoft blog post Announcing improvements to Enterprise Mode and Enterprise Site Discovery.
The even better news is that you can start implementing those changes today, on the Windows versions you currently have deployed, using Internet Explorer 11. When you roll out Windows 10, months or even years from now, you can use deployment tools to set Internet Explorer 11 as the default browser, and all the work you did will carry over.