Twilight

Twilight App – Frequently Asked Questions (FAQ)

1. What is the Twilight app?

Twilight is a screen filtering app that reduces blue light emission from your phone, tablet, or Wear OS device in the evening. It helps protect your circadian rhythm, making it easier to fall asleep by automatically adjusting your screen color temperature based on local sunset and sunrise times.

2. How does blue light affect sleep?

Blue light, particularly in the 460–480nm range, activates a photoreceptor in the eyes called melanopsin, which suppresses melatonin, a hormone crucial for regulating your sleep-wake cycle. Exposure to blue light in the evening can delay sleep onset by up to an hour, especially when using devices like smartphones or tablets before bedtime.

3. How does Twilight help improve sleep?

Twilight filters out blue light by overlaying a soft red filter on your screen after sunset. This reduces melatonin disruption, making it easier to fall asleep naturally. The filter intensity adapts in real-time to your location’s sunset and sunrise cycle.

4. Can Twilight be used for children?

Yes. Twilight can help prevent overstimulation in kids who use tablets or phones before bedtime by reducing blue light exposure that can cause hyperactivity or delay sleep.

5. Is Twilight compatible with Wear OS devices?

Yes. Twilight fully supports Wear OS, syncing the screen filter settings between your smartwatch and smartphone. You can also control the filter from a dedicated Wear OS Tile.

6. Does Twilight support automation?

Yes. You can integrate Twilight with Tasker or other automation tools to control its behavior based on custom triggers.
🔗 Automation Guide

7. Is it safe to use Twilight on AMOLED screens?

Absolutely. Twilight has been tested on AMOLED displays for over 5 years with no signs of burn-in or damage. In fact, by reducing overall brightness and balancing light distribution, it may even extend your screen’s lifespan.

8. What are the main benefits of Twilight?

• Improved sleep quality by reducing melatonin suppression

• Easier bedtime reading with reduced eyestrain

• Protection for sensitive eyes during migraines

• Enhanced longevity for AMOLED screens

• Full automation and Wear OS integration

9. What permissions does Twilight require, and why?

• Location: To calculate local sunrise/sunset times

• Running apps: To disable Twilight in selected apps (e.g., camera or games)

• Write settings: To adjust screen brightness

• Network: To connect with smart home lights (e.g., Philips Hue) for broader blue light control

10. Why does Twilight ask for Accessibility Service access?

To filter overlays on system elements like notifications and the lock screen, Twilight may request Accessibility Service access.
It is only used for screen filtering and does not collect personal data.
Learn more: Is Twilight a privacy risk?

11. Where can I find the official documentation?

Visit the official Twilight documentation here:
📄 http://twilight.urbandroid.org/doc/

12. Where can I learn more about the science behind Twilight?

Twilight is based on established scientific research regarding light and circadian rhythm. You can explore studies such as:

• Dijk et al. (2012) – Sleep and light phase shifts

• Gooley et al. (2011) – Melatonin suppression from room light

• Duffy & Czeisler (2009) – Light and human circadian physiology

• Wright & Gronfier (2009) – Light intensity and melatonin phase

• Santhi et al. (2008) – Bright light and attention during night work

• Zaidi et al. (2007) – Short-wavelength light sensitivity

For more references, see the complete list in the app documentation or Twilight Research.