F.lux is a free app for Mac, PC, and Linux, that runs in the background and subtly changes the color temperature of your computer screen to match the time of day. As the developers explain on the f.lux website, the screen is "warm at night and like sunlight during the day."
"When the sun sets, it makes your computer look like your indoor lights," f.lux says. "In the morning, it makes things look like sunlight again."
The idea is that matching the computer screen to your environment makes looking at your computer more pleasant.
F.lux may also help you sleep better because by decreasing the blue light emitted by your computer screen. Being exposed to blue light at night can confuse your brain and make it harder to fall and stay asleep.
As my colleague Melia Robinson wrote in her own review of f.lux earlier this year, "there is plenty of research that analyzes blue light's effects, but less - though still some - on lower temperate screen color effects on sleep. Further testing is required."
Here is what a MacBook Air display looks like with and without f.lux enabled:
Melia Robinson / Tech Insider
The computer on the right has f.lux enabled.
Even though it looks drastic, the adjustments to the color temperature of your screen throughout the day are so subtle that you don't notice that they're happening. But it's jarring to turn the app off at night and see the screen instantly return to "normal."
The only time I disable Flux is when I'm watching a movie or TV show on my computer and I want the colors to be true. To do that, you simply go to the menu bar and disable f.lux. This makes it easy to use the app if you're an artist or a photographer and you need colors to be accurate.
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