One of the biggest features promised for Microsoft's new Edge browser was support for extensions written in HTML and JavaScript. Google developed an API for such extensions for Chrome, and it is being substantially adopted by Firefox. Microsoft said that it, too, would adopt this API for Edge, but extensions didn't make the cut in the November Update.
Since the November Update, Microsoft has released a series of Insider Preview builds that so far didn't actually change a great deal that was visible. But the latest build, version 14291, changes all that, as it includes the first preview of the extension support in Edge.?Microsoft has three extensions thus far: two it developed itself (one to perform automatic translation of foreign language pages, another to enable mouse gestures), and a ported version of the popular Reddit Enhancement Suite (RES).
Right now, installing extensions is rather clunky—when this feature is released to end users, extensions will be included in the Windows Store and subject to some amount of vetting and oversight, but that's not plumbed in yet. Once installed, however, the extensions just seem to... work.
I use RES in Chrome, and from an initial poke around, RES in Edge does all the same things for me in the same way—because it's the same extension. Never-ending Reddit mode, inline expansion of images and videos, tagged users, all working in a Microsoft browser.
Early indications are that, at least for simple extensions, little needs to be done to convert a Chrome extension into one compatible with Edge (or Firefox).
Extension support is a big step forward in making Edge usable on a day-to-day basis. Another couple of changes in the new build further improve this. First is support for pinned tabs—tabs that shrink to a small icon in the tab bar and get recreated whenever the browser is reopened. Second, the address bar now has a "paste and go" option for navigating to URLs on the clipboard.