redshift

Start redshift with automatic location detection

$ redshift

$ redshift -O [3500]

$ redshift -t [5500]:[3500]

$ redshift -l [40.7]:[74.0]

$ redshift -x

$ redshift -o

$ redshift -p

redshift [-l lat:lon] [-t day:night] [-b day:night] [-m method] [options]

redshift adjusts the color temperature of the screen based on time of day, reducing blue light exposure in the evening. This can help reduce eye strain and improve sleep quality by matching screen color to ambient lighting.
During the day, the screen maintains normal color temperature (around 5500-6500K). As the sun sets, redshift gradually transitions to warmer colors (3000-4000K), reducing blue light that can interfere with circadian rhythms.
Location can be determined automatically using geolocation services (geoclue) or specified manually. The program runs continuously, adjusting temperature throughout the day based on calculated sunrise and sunset times.
Different backends support different display systems: randr for X11, wayland for Wayland compositors, and drm for console/framebuffer.

-l lat:lon

Set location (latitude:longitude) for sunrise/sunset calculation

Set color temperature in Kelvin (default: 5500:3500)

Set screen brightness (0.1-1.0)

Set specific color temperature immediately

One-shot mode; set temperature and exit

Reset color temperature to default

Print current settings and parameters

Adjustment method (randr, vidmode, drm, wayland)

Set gamma correction

Disable temperature transitions

Verbose output

Load configuration from file

Automatic location detection requires geoclue and appropriate permissions. If detection fails, specify location manually with -l.
Some applications (photo/video editing, color-critical work) may require accurate colors. Use redshift -x to temporarily disable adjustments or exclude specific times.
Wayland support depends on compositor support. Some Wayland compositors implement their own night light features.
Running multiple instances may cause conflicts. Use a single instance or integrate with your desktop environment's night light settings.

xrandr(1), xgamma(1), gammastep(1)