As long-time practitioners of the "dark theme" concept—it's still an option here at Ars for those who prefer light text on dark backgrounds—we're excited to see that Microsoft is extending the reach of its dark theme to include Explorer.

Windows 10 has a toggle to switch between the standard regular (dark text/light background) theme and the inverted dark theme.

For those who routinely use their computers in poorly lit rooms, the dark theme offers relief from the more traditional eye-searing white of the standard theme. For the most part, the only applications that follow this are new, modern applications built using the Universal Windows Platform. The latest Insider build, version 17666, extends that to Explorer, one of the most important and widely used traditional Win32 applications.

The new build has some other bits and pieces, too, including greater use of Microsoft's "Fluent" design language, but really, it's the dark Explorer that's exciting.