If you’re reading a book late at night on your phone or tablet, being able to set the interface to night mode is essential. Dimming the screen to black and reversing the user interface elements and text out of that background is much easier on the eyes in a darkened room, and easier on relationships, too, if your partner is trying to sleep next to you. I use this all the time in both Kindle and iBooks (the latter, by the way, is my preferred reading app because of the former’s eye-gouging use of justified text — how do people read in that app?!).

But if you’re reading your email, Instapaper, Twitter, your RSS client, or just about anything on your mobile device, there’s no night mode. In fact, outside of these book reader apps, I can’t think of another app that acknowledges the fact that sometimes users open devices in dimly lit environments, and that an interface with a single level of brightness may not apply to every situation.

Dim the House Lights

I’ll go even further and say that I believe it’s not just individual developers who are remiss here, but the operating system vendors themselves. There should be a globally available night mode option embedded into iOS, Android, etc., and that makes this concept a central tenet of mobile app design. Few things strike me as more integrally mobile than software that allows its hardware to respond to its environment, much as GPS chips and accelerometers do. The iPhone clearly has the ability to detect ambient light and adjust its screen automatically, which is helpful, but it does relatively little with this use case.

Apple should offer an API that lets developers specify a night mode interface for their apps, and that mode should be available from a system-wide switch. So instead of turning iBooks or Kindle to night mode individually, one flip of that switch would turn the whole device to night mode. In the beginning, of course, not every app will support this, but if Apple provides dim-light versions of the home screen, Mail, Messages, iTunes, Settings and other essential apps, that in itself would be a huge boon.

To some extent, this functionality exists already. Included among iOS’s accessibility controls is a switch that will allow you to invert the colors of the screen globally, turning everything dark to light and vice versa. It’s not a bad approximation of a true night mode, but it’s somewhat kludgy.

What would be even better is a setting with truer sensitivity to the user’s environment. I thought of this when I saw that the f.lux utility was recently upgraded after a long interregnum. F.lux adjusts the color temperature of your Mac, Windows or Unix desktop to match the ambient light in your environment, adapting to the cooler light of morning and the warmer light of the evening so that the screen you’re looking at feels like what’s around you.

I don’t use it myself, partly because as a designer the idea of messing with color temperature in so variable a way seems anathema to working with color. But it’s also true that since the advent of the iPhone and iPad I have little use for my laptop and desktop in low light situations — I don’t need this functionality in OS X, I need it in iOS. Everyone I know who uses f.lux, is a huge fan of it; I suspect similar functionality on iOS would be even more enthusiastically received.

Correction: folks point out that there are in fact a number of reading apps that have night mode, including Instapaper, Pocket, and at least one Twitter client, Twitterific. Still, I’d like to see more, and see OS-level support for it.