Night Shift is a built in software feature ofiOS andmacOS. It was introduced in 2016–2017 intoiOS iniOS 9.3 and intomacOS inmacOS Sierra 10.12.4.[1] The feature changes thecolor temperature of the display towards the warmer part of thecolor spectrum[2] that reduces some of the blue light from the screen.[3]Apple claims that the feature may help users have a better night's sleep by filtering blue wavelengths from the display, which suppressmelatonin biosynthesis.[4] The feature is similar to the functionalityf.lux provides.[5][6]
Changing the color temperature of the display from blue towards yellow (without dimming the screen) was shown to have no effect on sleep outcomes (sleep latency, duration, efficiency and wake after sleep onset) in a 2021 study on 167 college undergraduates[7] and to be insufficient for preventing the impact on melatonin suppression.[8][9] In mice, yellow colors disrupted the mouse body clock more than equally bright blue colors.[10]
The Night Shift feature is compatible with all64-bit iOS devices running on iOS 9.3 and above[11] andMacs from 2012 and later running on macOS Sierra 10.12.4 and above.[12]
The feature can be turned on in Settings (in iOS)[13] and in System Preferences (in macOS)[12] and can be toggled on or off manually in theNotification Center (in macOS)[14] or in theControl Center (in iOS).[2] The feature can be enabled or disabled withSiri in iOS[11] and macOS.[15] The feature can set so it is enabled at sunset and turn off at sunrise (the default) or turned on and off on a custom schedule.[2] The feature when set to enable at sunset and disable at sunrise relies on the user's approximate location to determine the time of sunset and sunrise.[16] The user can also customize the intensity of Night Shift in Settings (iOS)[2] or System Preferences (macOS).[17]
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