Among the many fascinating reveals in the opening keynote of the Microsoft Build 2015 developer conference—Android and iOS code running on Windows phones,holograms that can attach themselves to physical robots, and Visual Studio for Mac and Linux—was the Microsoft Edge browser.
Windows 10 Bug ArtInternet Explorer's more modern and fast successor, previously code-named Project Spartan, is now Edge, and one of its most notable new features is extensions. Edge also maintains Spartan innovations like page markup, reading view, and Cortana integration. It's also a Universal Windows app, meaning one application runs on PCs, phones, tablets, and whatever other Windows-running devices emerge.
Perhaps Edge's greatest asset is that it's not Internet Explorer, which, even after lots of improvements in speed and tightened design, was one of the most reviled pieces of software in history. Though Edge's icon still sports an "E," it really isn't IE. Even underneath, it runs a new page-rendering engine called…wait for it—Edge. Yes, that was the name of Project Spartan's engine, and it has now been elevated to the full product name. It tops IE's longtime Trident engine in speed and compatibility with new Web standards such as HTML5.
Windows 10 will still ship with IE11 for legacy compatibility, especially for corporate intranets and other entreprise Web apps, but it won't get new features and Edge will be the default browser. Find out more in the video and our list of upcoming features below.
Edge Browser ExtensionsExtensions are hardly a new capability in Web browsers, and even Internet Explorer had some extensibility, with toolbars, WebSlices, and Accelerators. But Edge brings the promise of full Firefox- and Chrome-style extensions.
In fact, Edge's extension developers will use the same JavaScript and HTML standard code used by those two competing browsers for their extensions. Furthermore, Microsoft's Vice President for PC-Tablet-Phone, Joe Belfiore, stated that extensions programmed for Chrome or Firefox would only require minimal coding to work in Edge. At the keynote, he demoed an extension for Reddit that would let you vote on stories and a Pinterest extension that let you share pages.
An important note about extensions in Edge is that the feature won't ship with Windows 10 RTM (release to manufacturing) this summer, but will come in a later update.
Edge Extension
CortanaWindows 10's voice assistant seems to be popping up everywhere, and Edge is no exception in this regard. When you land on a page for which directions make sense—say you're on a restaurant's webpage—Cortana pops up with her familiar blue circle in the browser toolbar proposing relevant information. You can also right-click on selected text to have Cortana find info about the selection.
Cortana Sidebar in Project Spartan
New-Tab PagePeople hit that bar atop the browser to open a new tab over a billion times a day, and Microsoft wants to make good use of that real estate. IE's new-tab page was actually one of the more useful among the browsers, all of which let you search and see thumbnails of your most-visited sites, but also let you re-open closed tabs and see site suggestions. In Edge, the new-tab page still shows top sites, but also app suggestions, weather, sports scores, and video suggestions. Interestingly, the page doesn't show an address bar, but you can type a URL into its search box.
Microsoft Edge New Tab Page
Reading ModeAnother feature that's been available in other browsers for years (particularly in Apple's Safari) but is making its debut in Microsoft's new browser is Reading Mode. This lets you strip out all the extra junk on a webpage aside from the main text and images —ads, sidebars, and so on—so you can read undistracted. 
Reading Mode in Project Spartan
Page AnnotationsThis one has not appeared on competing browsers from Mozilla, Google, and Apple, though I've seen a similar feature in the lesser-known Maxthon browser. Edge lets you mark up webpages with a highlighter or drawing tool and then share them as an image file in email or social apps.
Edge Markup
New Coding Support
A Build session on the Edge browser highlighted just how many forward-looking features Edge supports, and noted that the browser doesn't appear as IE to sites, so they're more likely to work as they do in Firefox, Chrome, and Safari (mobile and desktop). The browser will support Object RTC, a newer form of WebRTC, the protocol that allows sites access to media communications; think Skype via a Web browser. Here's a slide showing other new features in Edge:
New Edge Browser Features
An Edge Among BrowsersMicrosoft's new browser shows promise, and seems to be moving in all the right directions—faster speed, more standard support, extensions, and even a couple of unique features like page markup and Cortana integration. The fact that it will deliver the same experience on every device size—from Raspberry Pi to HoloLens to Xbox One—is another advantage. To try it out (on a non-critical PC), you can join the Windows Insider program and install Windows 10.