There was a stretch when every Linux desktop wanted a small resident program to keep the screen from burning at midnight. Redshift did it by reading the sun rather than the clock: work out where the sun sits, warm the display as it sets, cool it again at sunrise. The repository went read only in April 2026 and the last release stays at 1.12, yet the packages are still in most distributions.

An old tool that shifts colour through the gamma table

What Redshift does fits into one sentence. It pushes the colour temperature of the screen downward according to the surroundings, so that staring at the display at night stings less. It does not touch the brightness of the panel, and it does not enter the colour management of the graphics driver. Instead it rewrites the gamma correction table of the display and alters the ratio between the red, green and blue curves; leave a little more red in the mix and the picture turns warm.

The method is simple, and because it is simple it left something behind. The project documentation says so plainly: the gamma table was a workaround for the absence of a common interface for colour adjustment, and as long as the tool stays on that road, a number of problems cannot really be solved.

Deciding when to turn red

The input is the altitude of the sun. The program takes the current location, works out how many degrees above the horizon the sun sits right now, and interpolates the colour temperature across the stops written in the configuration. The location can be fixed by hand as a pair of coordinates, or handed to the system location service and kept current; version 1.12 turned the second path into a continuous push, so a change of place no longer needs a restart.

Several stops fit into one day: one for daylight, one around sunset, one for the night, each carrying its own colour temperature and gamma value. The status window names the period in force, whether day, transition or night, so one glance shows which stop is running.

Following the sun is optional. The same release added a schedule, where you write which hours use which temperature, which suits a regular routine or anyone who stays indoors all day.

Configuration and two ways to run

It runs without a configuration file. The defaults are 6500K by day and 4500K at night, and those numbers were settled in 1.12. For finer control the settings move into a file: on Linux and macOS under a redshift subdirectory of the user configuration directory, on Windows under the local application data directory. The older path is still read, but it is marked as discouraged.

There are two entry points. The command line version only adjusts colour, and its options all live in the help output. The one whose name carries a gtk suffix adds a status icon; a press suspends the effect temporarily and shows the current temperature and period. A hook can be attached to enabling and disabling, and 1.12 added that hook.

What 1.12 changed

According to the release notes, 1.12 did five things: the location provider became continuously updating, a schedule configuration arrived, the configuration file moved to a new directory, hooks fire on enable and disable, and the defaults settled at 6500K and 4500K. Alongside those, RandR mode allows the shift on only some outputs, so a multi-monitor desk can leave one panel at its native colour.

Where the edges are

The most common problem is a driver that will not cooperate. On some graphics drivers the gamma table is read only, and the failure takes one of two shapes: the program reports an error, or the adjustment is silently dropped and the screen does not move at all. Full screen applications that take over the output bypass this layer, so seeing no effect inside a game is expected.

Location can go wrong too. When the system location service is switched off, any path that depends on it has no coordinates, and a hand written pair in the configuration becomes the fallback. The brightness options change gamma rather than the backlight, so on a laptop pressing them does not feel like the screen really dimming.

After the archive

The repository was archived read only by its author on 1 April 2026. The last release, 1.12, dates from May 2018, and commits on the main line stop in June 2020. The documentation itself concedes that desktop environments have been building the same feature in as a component, and those implementations dodge most of the gamma table trouble, which usually makes them the better first choice.

Most distributions still carry the package in their repositories, and it works once installed; an upstream archive does not pull it from the shelves overnight. What has gone is anyone to fix the compatibility problems new kernels and new drivers bring. On a machine whose gamma table cannot be read, there is no route left but a different one.

That is not the same as useless. The configuration file can be very precise, the command line slips into scripts, and on older machines and lightweight desktops it still saves effort. Treating it as a resident program that is set once and then forgotten suits it better than adjusting it on the spot.

Whether to use it comes down to whether that granularity is needed. Following the sun, living inside a script, shifting only one of several panels: it remains a ready answer. Wanting nothing more than a less harsh screen at night means the setting already built into the system is enough.