Spartan is Microsoft’s next generation modern browser. It can be thought of as an evolution of the universal app metro IE browser that shipped with windows 8, alongside the desktop IE. It is/was stripped down, simpler, did not support plugins etc. It includes many user friendly capabilities such as inking, annotations and integrated Cortana personal assistant. Spartan is a code name and will likely not be the final name for the browser.
Spartan, at this point according to Microsoft, is for Windows 10 (and later) only. There are no announced plans for Windows 7 or alternative OSes. However given the company’s extended focus beyond Windows, and the intent to bring Cortana to IOS and Android, it is certainly very possible that it will make its way onto those platforms. Windows 7 however, is less likely as a target as Microsoft would rather the installed base upgrade to Windows 10. This means that for most enterprises, Spartan is not a major issue until they migrate to Windows 10, which for most, is a 2017, or later effort.
Spartan is being positioned as a consumer offering, and enterprises will be able to use IE11 (it may be called just IE) with “Enterprise mode” for backward compatibility. This backward compatibility will also exist in Spartan. Spartan is likely to be somewhat compatible via enterprise mode, but for enterprise legacy backward compatibility, IE will be recommended.
There are several motivations for a new browser, or at least a new name and brand. First, market perception of IE is not great so a change is beneficial from a naming perspective. Antitrust implications deriving from the company’s insistence of making the browser part of the OS are also likely playing a role. And, related to that, the restriction that does not allow for multiple versions of IE to be installed on the same Windows system has led those who need a modern browser and a legacy browser to seek alternatives as their modern one as part of a two-pronged browser strategy.
My Gartner Research Note from last year (subscription required) https://www.gartner.com/doc/2678415/twopronged-approach-browser-strategies-allows describes the two-pronged browser strategy used, one way or another, by many enterprises today. In many ways, Spartan can be thought of as Microsoft’s own use of a multipronged browser strategy. IE becomes legacy and Spartan is the modern/current one.
Spartan is best thought of as part of Microsoft’s own two pronged browser strategy and it is the future. Not just for consumers.