Twilight: Blue light filter
com.urbandroid.lux
by Petr Nálevka (Urbandroid)
Screenshots
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About this app
Are you having trouble falling asleep? Are your kids hyperactive when playing with the tablet before bed time?
Are you using your smart phone or tablet in the late evening? Are you sensitive to light during migraine?
Twilight may be a solution for you!
Recent research suggests that exposure to blue light before sleep may distort your natural (circadian) rhythm and cause inability to fall asleep.
The cause is the photoreceptor in your eyes, called Melanopsin. This receptor 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 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. See references below..
The Twilight app makes your device screen adapt to the time of the day. It filters the flux of blue light emitted by your phone or tablet after sunset 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.
Documentation
http://twilight.urbandroid.org/doc/
Get more from Twilight
1) Bed reading: Twilight is more pleasant on the eyes for night reading. Especially as it is able to lower the screen backlight far below the ability of the backligt controls on your screen
2) AMOLED screens: We have tested Twilight 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.
Basics on circadian rhythm and the role of melatonin
http://en.wikipedia.org/wiki/Melatonin
http://en.wikipedia.org/wiki/Melanopsin
http://en.wikipedia.org/wiki/Circadian_rhythms
http://en.wikipedia.org/wiki/Circadian_rhythm_disorder
Permissions
- location - to find out your current sunset/surise times
- running apps - to stop Twilight in selected apps
- write settings - to set back-light
- network - access smartlight (Philips HUE) to shield you household light from blue
Accessibility Service
In order to filter also 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. Please read more about this at https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/
Wear OS
Twilight also syncs your Wear OS screen with your phone's filter settings. You can control filtering from a "Wear OS Tile".
Automation (Tasker or other)
https://sites.google.com/site/twilight4android/automation
Related scientific research
Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans Derk-Jan Dijk, & Co 2012
Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans Joshua J. Gooley, Kyle Chamberlain, Kurt A. Smith & Co, 2011
Effect of Light on Human Circadian Physiology Jeanne F. Duffy, Charles A. Czeisler 2009
Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans Claude Gronfier, Kenneth P. Wright, & Co 2009
Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans Kenneth P. Wright, Claude Gronfier & Co 2009
The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work Nayantara Santhi & Co 2008
Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina Farhan H. Zaidi & Co, 2007
Are you using your smart phone or tablet in the late evening? Are you sensitive to light during migraine?
Twilight may be a solution for you!
Recent research suggests that exposure to blue light before sleep may distort your natural (circadian) rhythm and cause inability to fall asleep.
The cause is the photoreceptor in your eyes, called Melanopsin. This receptor 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 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. See references below..
The Twilight app makes your device screen adapt to the time of the day. It filters the flux of blue light emitted by your phone or tablet after sunset 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.
Documentation
http://twilight.urbandroid.org/doc/
Get more from Twilight
1) Bed reading: Twilight is more pleasant on the eyes for night reading. Especially as it is able to lower the screen backlight far below the ability of the backligt controls on your screen
2) AMOLED screens: We have tested Twilight 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.
Basics on circadian rhythm and the role of melatonin
http://en.wikipedia.org/wiki/Melatonin
http://en.wikipedia.org/wiki/Melanopsin
http://en.wikipedia.org/wiki/Circadian_rhythms
http://en.wikipedia.org/wiki/Circadian_rhythm_disorder
Permissions
- location - to find out your current sunset/surise times
- running apps - to stop Twilight in selected apps
- write settings - to set back-light
- network - access smartlight (Philips HUE) to shield you household light from blue
Accessibility Service
In order to filter also 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. Please read more about this at https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/
Wear OS
Twilight also syncs your Wear OS screen with your phone's filter settings. You can control filtering from a "Wear OS Tile".
Automation (Tasker or other)
https://sites.google.com/site/twilight4android/automation
Related scientific research
Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans Derk-Jan Dijk, & Co 2012
Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans Joshua J. Gooley, Kyle Chamberlain, Kurt A. Smith & Co, 2011
Effect of Light on Human Circadian Physiology Jeanne F. Duffy, Charles A. Czeisler 2009
Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans Claude Gronfier, Kenneth P. Wright, & Co 2009
Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans Kenneth P. Wright, Claude Gronfier & Co 2009
The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work Nayantara Santhi & Co 2008
Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina Farhan H. Zaidi & Co, 2007
What's New
- Latest API target requirement on Wear SO
- New libraries
- New libraries
App Information
Version Name
13.8
Version Code
524
File Size
6.4 MB
Min SDK
Android 16+
Target SDK
Android 33
Developer
Petr Nálevka (Urbandroid)
Contact
Website
Content Rating
Everyone
Package Name
com.urbandroid.luxPermissions Required
This app may request the following permissions:
Recent Reviews
AJ Jean
5.0★
Great app. Have been using it for many, many years now! Really helps turn my brain off when I need to use my phone (tablet, etc.) but am still trying to get my brain/ eyes into sleep mode! I always recommend this app to anyone having trouble falling asleep! That bright blue/ white light from our devices is a sleep killer!
Margaret Horn
4.0★
Great app , indispensable, except that it doesn't always come on automatically when you turn your phone on at night. Either there is a delay, or you have to turn it on manually. Also, sometimes it shuts off on ots own. In the intervening time, you are going to be exposed to the Blue light that interferes with sleep. Hi Petr , got your response. Seeing as so many people use Android, can you do something about this? I haven't had issues with other apps. Thank you!
flower child
5.0★
okay, hands down, best blue light filter I've ever had. it's easy to use, you can adjust the colour/temperature, brightness, and intensity. hardly any ads, slowly adjusts so you don't just suddenly have a red screen lol. i love it, and I'd definitely get the paid option if I could, but it's amazing even without it. and best of all it doesn't randomly stop and filters notifications too. :) 10/10 edit: as of july 2025, my review still remains the same. just wish i could use it on desktop too lol
Jamie Kinthaert
1.0★
This app has been crashing multiple times today out of nowhere (I've had this installed for 1+ years). The problem is, everytime it crashes, it opens up my Gmail and tries to send the Crash Report with everything filled out, which almost feels like some Phishing attempt or Malware attack. You need to remove this and allow users to choose whether or not to report crashes; instead of writing some code that opens up their Mail app and tries to send e-mails on it's own.
A Google user
5.0★
So far, it dose everything I had hoped, namely making it possible to dim my screen further. I like the red tone. Not sure if it really decreases the frequency of light that destroys melatonin or not, but it is soothing and makes using the phone in the dark more pleasant. Update: All of a sudden it has stopped working properly. It appears to still be running, but there's no change in my screen color or brightness. I've checked the settings and I have rebooted my phone. I'll try to reinstall.
Meghann O'Malia
5.0★
great, compact little app. been using it for years. really helpful when I want to wind down for the night by playing a little sudoku and i need a dim screen. it's very easy to customize how much color filtering you want. I wish it were easier to turn off twilight manually when I forget to turn off the filter when I'm out and about in the morning.
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