Compatible with devices running iOS5/6/7/8.

f.lux warms up your screen to match your lighting at night.

If you see the f.lux app crash when launched, it seems to be incompatible with Medusa right now: thanks reddit for the report.

Older iOS versions: Sometimes when updating Cydia and f.lux at the same time, the Reboot Device button will not work, and f.lux will not run. If you encounter this, please reboot the device (don't respring) to fix it.

Have you ever seen someone using a mobile phone in a bar or dark restaurant and noticed the bright blue glow coming from the screen? f.lux fixes this.

Select the type of lighting in the room you're in at night, and then forget about it.

Each evening at sunset, f.lux warms up the colors on your phone. At dawn, f.lux returns your phone to daylight colors.

We made f.lux because one day we noticed that all our laptops were the wrong color temperature at night. They looked fine during the day, but at night, they were much too blue. We realized that looking at the sun all night long might not be such a good idea.

After researching blue light's effects on health, we found lots of evidence that color matters even more than brightness. And it turns out that timing matters, too: Blue light during the day is great for your circadian rhythm. Blue light at night is not.

Sleep researchers have just begun studying the effects of night-time usage of laptops, cell phones, iPads and other devices that emit blue light. Evidence suggests that even just a little extra blue light at night can keep you awake later and negatively affect the quality of your sleep.

Our users say that f.lux prevents eyestrain. They also say that it's easier to wind down and go to sleep after using a f.lux-enabled device at night. Plus, you'll never glow blue in a restaurant again.

You can use f.lux because it makes you sleep better, or you could use it because it just makes you look better. Either way your eyes will thank you.