Switching to HTML5 extensions in Edge improves security in more ways than just removing ActiveX. "We're 64-bit by default now," he pointed out, "that's something we've tried to do for the longest time but we've been held back because most extensions are 32-bit."
The Edge browser has multiple sandboxes and multiple processes. The interface that you see when you use it, with the tabs and toolbar and other controls, is a Windows 10 app running in a very restricted app container, a Microsoft spokesperson explained to TechRadar. The browser interface runs in its own process, and each tab runs in its own process as well, so they don't interfere with each other, and there are other processes that broker communication between them.
And the pages are rendered by the Edge rendering engine, with JavaScript run by the Chakra engine. Those are part of the Windows OS and there are two versions of both the rendering and JavaScript engine – one for Edge and one for IE (so the IE version of the JavaScript engine has support for VBScript, but the Edge JavaScript engine doesn't).
For extensions, the script of the extension runs in the context of a tab, and the script host is a separate process, which you can think of as a separate hidden tab; again, that isolates things for security. So the parent process that's the browser frame can do things like opening the camera, but a child process wouldn't get access to that. That tab isolation is why you can see multiple tabs as thumbnails on the taskbar.
And this also improves performance, we were told, because a JavaScript extension running in the background doesn't interfere with other tasks (which should avoid the problems some Chrome users see with extensions slowing down the browser).
Extensions on phones?
The Edge team is talking to the developers behind all the popular extensions, including the ad blockers. It's possible that those will replace functionality that's in IE, like Tracking Protection Lists. Those are built by third parties but distributed by Microsoft through the Internet Explorer Gallery site. Extensions will be distributed through the Windows Store, like apps, which means there is already a system for developers to submit and update them.
That also means there's a mechanism for businesses to curate a list of extensions they want to make available to users through the company version of the Windows Store (or potentially even block extensions for certain users).
Edge on Windows 10 for Phones handsets and tablets is the same engine as Edge on the PC (and on Xbox and HoloLens), and the interface adapts to your screen resolution.
That doesn't mean that extensions will definitely be available on phones though – the team is still looking at the impact that would have on performance and battery life, especially on smaller handsets with less memory and less powerful processors (where smaller screens might make it awkward to use extensions inside a page). They plan to use telemetry that will show whether the performance on different phones is good enough for extensions like ad blocking that do make sense on smaller screens.
