At a Glance
- Can be disabled for only one hour at a time
This utility changes your monitor’s color temperature at night–and may help you help avoid insomnia.
Have you ever gone by a house where the TV was on at night, and
noticed the bluish glow emanating from the screen? Or woken up
early and switched on your monitor (or smartphone) to be blinded by
a burst of bright white light? With f.lux, this doesn’t have
It turns out monitor brightness isn’t the only thing to
blame when this happens. Color temperature, measured in units
called kelvin, has a lot to do with it. The simplest way to explain
color temperature is in terms of tint: You know how the color white
sometimes seems “warm” (a bit reddish) and sometimes
“cool” (bluish)? That’s color temperature at
With their typical cool tint, computer monitors look great
during daytime hours. But once the sun sets, monitor screens look
much better if their color temperature is adjusted accordingly. And
that’s what f.lux does.
F.lux takes your location and the current date into account, and
can tell when the sun is going to set every day. Right around that
time, with F.lux running in the background, you will notice a
“virtual sunset” happening on your monitor. Everything
seems to mellow down a little bit, every shade of color growing
slightly warmer and cozier than it was during the day.
You can set the adjustment to happen very gradually over the
course of a full hour, or quickly (in twenty seconds). When using
the fast adjustment option, things visually slow down while the
adjustment is being done, but it only takes a moment. Adjusted, the
monitor looks completely natural, and after a while you may even
forget the color temperature was ever changed.
If you’re doing color-sensitive work, you may want to
disable f.lux temporarily. Unfortunately, you can disable it for
only one hour–no more, no less. If you need to disable it for more
than an hour, you simply have to quit the app (and then may forget
to switch it back on–that’s what often happens to me, at
According to research papers
cited on the Flux website, insomnia may be linked to blue light.
There is no conclusive evidence on this, but many practitioners
recommend avoiding blue light within two hours of sleep.
After working with f.lux for over a year, I can say that it
makes it easier for me to go to sleep at night after spending some
time in front of the screen. If I could just disable it for more
than an hour at a time, it would be just about perfect.