Free, open-source alternatives to f.lux

f.lux adapts the colour of a computer's display to the time of day. After you set your location and the kind of indoor lighting you have, it warms the screen after sunset and returns to daylight colours in the morning without further input.

The open-source apps below do the same job of warming the display in the evening. Abendrot handles the colour shift itself, adjusting each display around local sunset and falling back to a tint where direct control is not available. Shifty takes a different route: it builds on macOS Night Shift, adding finer temperature control and exceptions for colour-sensitive apps, so it depends on Night Shift being supported on your Mac.