Who each app is for
f.lux is for people who want warmer evenings on every computer they own, timed to the sun where they live and to when they wake up. Because it is free there is nothing to weigh up. It also runs on Windows and Linux, so if your week is split between a Mac at home and a PC at work, the same app does the same thing on both.
Sundown is for people who use a Mac late, often in a dim room, and want the screen warmer than f.lux will take it. It sits in the menu bar with a warmth ladder from ordinary daytime white down to a deep red, so you can see the exact number you are on and move it in small steps. You pick a preset, or set a schedule by clock time and let it warm the screen for you.
What f.lux does well
It is free, and that matters. It is cross-platform, which Sundown is not. And it can switch itself off while an app you select is active, which is useful when you are editing photos or grading video in the evening and need colour you can trust. Sundown has no per-app setting; turning it off is one global toggle. If any of those three is the thing you care about most, f.lux is the better fit.
How warm each one goes
The warmest f.lux setting is very warm. That is already a deep orange, far warmer than a daytime screen, and plenty of people never want more. Sundown starts where f.lux stops and keeps going to its warmest, where the screen turns a deep red. Between daytime white and that deep red you can stop anywhere, in small steps, and Sundown shows the number so you always know where you are.
Whether that extra range is worth paying for depends on how you use your Mac at night. If f.lux at its warmest looks warm enough to you, it is, and you can keep your money.
Scheduling and presets
Both apps let you choose how warm the screen gets in the evening, and they time it differently. f.lux works from the sun and your sleep: you give it your location and your usual wake time, and it applies its own colour temperatures for daytime, sunset and bedtime. Its presets include Recommended colors, Classic f.lux and Working late, and with Custom colors you drag each period to the warmth you want. Sundown works from the clock: you choose a warmth preset from the menu bar, or build a schedule by clock time so the screen warms in the evening on its own. If you want warmth tied to sunset and your wake time, f.lux is built around that. If you would rather set the hours yourself, Sundown is built around that.
Updates on the Mac
f.lux still ships: its Windows build is dated 8 April 2026. The Mac build hasn’t changed since 17 May 2023. Both dates come from the download files on justgetflux.com. Our guide to f.lux for Mac shows how to install it and how to check those dates yourself. The company is active, and its co-founder still answers questions on the f.lux forum, so this is a point about the Mac download, not about the people behind it. Sundown’s latest Mac release, 1.6.1, went out on 21 October 2026.
Price and platforms
f.lux is free on macOS and Linux, and free for personal use on Windows. Sundown costs $4.99 a month or $39 a year, both with a 7-day free trial, or $79 once for a lifetime licence. Sundown runs on macOS 12 or later, on Apple Silicon and Intel Macs. Sundown for Windows is coming soon. There is no Linux version.
Which should you choose?
Choose f.lux if you want something free, a deep orange is warm enough, you also use Windows or Linux, you want warmth timed to sunset and your wake time, or you want it to turn itself off while an app you select is active.
Choose Sundown if you want the screen warmer than a deep orange, all the way to a deep red, if you want a schedule that runs on clock times you set, or if you want a Mac app that is still getting Mac releases.
If you can’t decide, the trial makes it easy to try both: quit f.lux, run Sundown for an evening, and compare. For a wider look at the options, our guide to f.lux alternatives for Mac covers more apps, and Sundown vs Night Shift compares Sundown with the filter built into macOS.