f.lux is a free Mac utility that automatically shifts your display's white point and colour warmth based on your local time of day and geographic position, reducing the blue-light output that disrupts melatonin production in the hours before bed.
What is f.lux?
f.lux is a background daemon that continuously adjusts your monitor's colour profile throughout the day — cooler and brighter at noon, progressively amber as the sun sets in your specific location. Unlike the built-in Night Shift on macOS, f.lux has been doing this since 2009, with a level of configurability that Apple's native option simply cannot match.
Once you drop your latitude/longitude into its tiny settings panel, the app largely vanishes from your life. It runs at login, lives in your menu bar, and does its job without asking for anything in return. I've had it installed on every personal Mac I've owned for the past eight years, and I notice its absence immediately whenever I work on a machine that doesn't have it.
What does f.lux do best?
f.lux excels at gradual, perceptible-but-not-jarring colour transitions that mirror the natural arc of daylight — something static toggle switches like Night Shift can never replicate. The transition speed is adjustable: you can choose a slow 60-minute fade you barely register, or a snappy 20-second change for those late-night screenshot sessions where you need to see accurate colours for a moment.
A few features separate it from every alternative:
- Movie mode — temporarily disables the shift for 2.5 hours, useful when colour accuracy actually matters at night.
- Backwards alarm clock — warns you if staying up late is about to push past a self-set sleep target.
- App-specific whitelisting — apps like Lightroom or Photoshop can be excluded so the daemon stands down while you're colour-grading.
- Daytime fading — beyond just night mode, you can also tone down the colour temperature at midday in bright sunlight, which anyone working in a sun-drenched room will appreciate.
The colour curves are impressively fine-grained: you set separate Kelvin values for daylight, sunset, and bedtime, letting you tune from a gentle 5000 K working temperature all the way down to a candle-warm 1900 K for the final hour before sleep.
Is f.lux free?
Yes — f.lux is completely free to download and use with no subscription, no nag screens, and no feature paywalls. The developers accept donations but have never monetised the app itself. It installs in seconds from justgetflux.com or via Homebrew Cask (brew install --cask flux).
Who should use f.lux?
f.lux is for anyone who looks at a Mac screen after dark — which, in practice, means everyone. It pays back its tiny setup cost most obviously for night-owl developers, writers who keep strange hours, and anyone who's ever gone to bed after a late work session and found themselves staring at the ceiling at 2 a.m. wondering why sleep won't come. Shift workers and people with irregular schedules benefit the most, since f.lux lets you define a custom wake time rather than assuming a 9-to-5 rhythm.
Designers and photographers should note that f.lux does alter colour perception at night — that's the point. The app-exclusion and Movie Mode features exist precisely for those moments. If your workflow demands spot-on colour accuracy at midnight, keep a keyboard shortcut to the pause function ready and plan around it.
How does f.lux compare to Night Shift?
Night Shift, Apple's built-in option in Display Preferences, covers the basics: it warms the screen at sunset and cools it at sunrise. But it offers only a single coarse slider for intensity, no per-app exceptions, no adjustable transition speed, no Kelvin readout, and no bedtime alarm. f.lux exposes all of that. Night Shift is the better option only if you want zero configuration and have no unusual sleep schedule — which rules out most power users. The two cannot run simultaneously; you'll pick one and forget the other quickly.
What are the best f.lux alternatives?
Aside from Night Shift, Lunar is worth a look if you want external-display brightness and colour management in a single panel — it supports f.lux integration rather than replacing it. Iris offers similar colour-temperature controls with added blue-light filtering and a paid tier. For most people, though, f.lux is the category winner: it has the longest track record, the deepest configurability, and the price is hard to argue with.
