Here's a closer look at the new Office Online extension for Microsoft Edge

[Windows Central]

Throughout the development of the Windows 10 Anniversary Update, we have seen some extensions coming to Microsoft Edge, and now as we get closer to the final release of the next major update of Windows 10, Microsoft is officially adding Office Online to the list of extension for the browser.
Microsoft is officially releasing the new extension alongside Windows 10 build 14366 for PC, and it's a requirement that you're running this or a later pre-release version of the operating system.
Office Online is a simple extension that plugs into Microsoft Edge to provides users the ability to quickly create and edit Word, Excel PowerPoint, OneNote, and Sway documents on the web without the need of having to install the apps locally on your computer.

Full story from the WindowsCentral blog...