Twilight is an app that can help you sleep better by filtering the blue light emitted by your phone or tablet after sunset. Recent research suggests that exposure to blue light before sleep may distort your natural (circadian) rhythm and cause inability to fall asleep. The photoreceptor in your eyes, called Melanopsin, is sensitive to a narrow band of blue light in the 460-480nm range which may suppress Melatonin production - a hormone responsible for your healthy sleep-wake cycles. In experimental scientific studies, it has been shown that an average person reading on a tablet or smart phone for a couple of hours before bed time may find their sleep delayed by about an hour.

The Twilight app adapts your device screen to the time of the day and protects your eyes with a soft and pleasant red filter. The filter intensity is smoothly adjusted to the sun cycle based on your local sunset and sunrise times. You can also use Twilight on your Wear OS device. The app is more pleasant on the eyes for night reading and is able to lower the screen backlight far below the ability of the backlight controls on your screen.

Twilight may also be beneficial for those with AMOLED screens. The app has been tested on an AMOLED screen for 5 years without any sign of depletion or over-burning. If properly configured, Twilight causes less light emission (by enabling dimming) with more equal light distribution (dark areas of the screen such as the status bar get tinted). This may in fact increase your AMOLED screen life time.

In order to filter your notifications and lock screen, the app may ask for enabling Twilight Accessibility Service. The app uses this service only to better filter your screen and does not collect any personal information. The app requires permissions such as location, running apps, write settings, and network access smartlight (Philips HUE) to shield your household light from blue.

In conclusion, Twilight is a helpful app that can improve your sleep quality by filtering the blue light emitted by your phone or tablet after sunset. The app adapts your device screen to the time of the day and protects your eyes with a soft and pleasant red filter. The app may also be beneficial for those with AMOLED screens and requires permissions such as location, running apps, write settings, and network access smartlight (Philips HUE) to shield your household light from blue.