Introduction and easy porting
If there are features you're hoping to see that aren't yet in Microsoft's new Edge browser, be prepared to wait until this autumn. The most important of those incoming features is extension support, which may also be how Microsoft addresses the question of Tracking Protection Lists and ad blocking – and it won't be in Edge at RTM.
Autumn is also when we'll get more of the Cortana features we saw demoed in January, along with Object RTC (the upcoming version of WebRTC, which will make it easier for developers to build web apps for making voice and video calls) and pointer lock. The latter lets you lock the mouse pointer into your browser if you're playing a game, so you don't accidentally click somewhere else and lose the game.
This strategy is part of what Microsoft means by calling Edge an evergreen browser – especially because it's what web apps in the Windows Store are based on – although the update schedule isn't yet set. So far, Edge has been getting new features about twice a month as part of the Insider program, and the Windows Insider program will continue after launch, but even users who aren't Insiders will get frequent updates.
"Being locked to the next version of Windows and rolling releases are now the same thing," Sean Lyndersay of the browser team said at Build. "Windows 10 itself will be doing rolling releases and users will be brought along. The entire app platform on Windows 10 is going to be kept evergreen across the entire consumer base and Edge will move along with that. We haven't worked out the exact cadence of whether it's 45 days or 90 days or 73 days or whatever, though."
The team is also looking at using release numbers to make it clearer for developers which features the Edge browser has in different flights.
The demos the Edge team gave of extensions running in the browser at the recent Build conference used a version of the browser that isn't yet released, and used extensions that the Edge team adapted after getting the extension code from the original developers, like the Reddit and Pinterest extensions (the latter is pictured above). In both cases, he said, "we were able to bring it over to Microsoft Edge almost unchanged, we were able to bring it up with very few changes to the extension itself."
"We want to make it very easy for developers to bring extensions to Edge," he said, but also noted that "we would like to have extensions do unique things with features we have in the browser." The Skype team has written an extension that picks up phone numbers on the page and the Bing Translate team has written an extension that switches Edge into reading view and translates the site from another language at the same time (because if you can't read the language of a site, the links and navigation on the page aren't that useful).
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.
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.
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).
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.