This is the actual Spartan interface.
And this is a mockup of the GUI made by Neowin:
This is what we know about Spartan so far:
- Spartan is just a codename.
- Default browser of Windows 10
- New GUI looks more like Chrome and Firefox.
- Modified Trident engine
- Extension support
- Borderless window
Let me know if I forgot anything on the list in the comments.