Windows 10 helped to bring about the current trend of offering a dark mode within apps and websites. Whether you use dark mode to help rest your eyes, or purely as an aesthetic choice, the option of turning out the digital lights is something Windows 10's provided since the start.
Windows 10 defaults to a light desktop theme which renders most surfaces in a bright and clean white. To activate dark mode, oppen the Settings app (Win+I keyboard shortcut) and click Personalization > Colors. Under "Choose your colour," click the "Dark" option.
Alternatively, you can select the "Custom" option which allows you to distinguish between the Windows UI and your apps. The "default Windows mode" option applies to Windows interface elements, such as the taskbar and Start menu. The "default app mode" choice will apply to apps from the Microsoft Store.
The Windows interface and most Microsoft Store apps, Settings included, will immediately switch to a deep black look. Windows 10 uses much more black than most app and website dark themes, which tend to favour a dark tinted grey.
Windows 10 now does a good job of applying dark mode across the entire operating system. You'll see it picked up in File Explorer, the operating system's interface surfaces and almost all Microsoft Store apps and controls. However, it's not able to impact desktop apps and the vast majority of websites.
We've got individual guides on setting up some of the most popular apps to use their own dark modes. Microsoft Office is a particularly significant desktop suite which includes comprehensive dark theme support independently of Windows' global settings. Many other third-party apps, such as Chrome, Firefox, Adobe software and leading text editors, have the option of a dark theme either included or available from an extension store.
When it comes to websites, your options are determined by the site's publisher. Many leading web apps, such as Microsoft's Outlook.com, and some blogs and news sites now offer a dark theme. The location of the setting can vary significantly by site and will need to be applied on a per-site basis.
An emerging web standard enables websites to determine whether you have selected a light or dark theme within your operating system. The site can then adjust its own theme accordingly. We're using it here on OnMSFT, so you should observe the site switching between a light and dark look as you toggle the "default app mode" in Windows 10's Settings. You can expect to see more sites adding support for this functionality over the next year, gradually turning the Settings app into the single place to enable dark mode.