The blue light emitted from the backlit LED screen of your computer, smartphone, tablet, or TV at night is not only hard to look at, it can also interfere with your sleep-wake cycles. Dimming your screen can help, but it’s the blue wavelength in particular that has been shown to suppress the natural evening rise in melatonin (a hormone that promotes sleepiness).
A number of tech companies are starting to address the issue by incorporating built-in blue light filters that can change the color temperature of your screen in the evening. Apple’s iOS 9.3 will have Night Shift, Google has added Night light to Google Play books, and Amazon Fire has Blue Shade.
The app F.lux is available for Windows, Mac, Linux and jailbroken iPhones and iPads. There are five standard settings, from most blue light to least: daylight, fluorescent, halogen, tungsten, and candle. The latter three settings will seem dim at first, but people do adjust after a few days.
There are similar apps for Androids called Twilight and Night Filter, Redshift is an option for Linux, and for other smartphones, there are blue-light-filtering screen protectors such as the Tech Armor Retina shield.