ZDNet's Mary Jo Foley reports that this new browser is a departure from Internet Explorer, the Microsoft browser whose relevance has waned in recent years. According to Foley, it will be a "lightweight" browser that looks and feels more like the Google Chrome and Mozilla Firefox browsers. But her sources also indicate that Spartan will be offered alongside IE when Windows 10 debuts next year.

With Mozilla Firefox and Google Chrome grabbing so much of the desktop market—and Apple Safari, Google Chrome, and Google's Android browser dominating the mobile market—Internet Explorer is no longer the force it once was. There was a time when it handled about over 90 percent of all web traffic on desktop and laptop machines, but according to research outfit Net Applications, its share has now dropped to 58 percent. On mobile, its share is about 2 percent.

Spartan attempts to address both these markets, according to Foley. Windows 10 is designed to run across a wide range of devices, and according to Foley, the new browser will be available on phones and tablets as well as laptops and desktops. It's unclear whether Spartan will run on Android, Apple's iOS, and other operating systems that compete with Windows, but Foley says there's a chance it will.