The fundamental difference

f.lux

Color temperature shift

f.lux adjusts your screen's Kelvin value — making it warmer (more orange) or cooler (more blue). This broadly reduces blue light output, which helps with circadian rhythm and sleep. But it doesn't target specific wavelengths.

Nox

Spectral wavelength filtering

Nox uses 41-point spectral transmittance curves to filter specific wavelengths. The Migraine Precision preset drops to 2% transmittance at 480nm (the melanopsin peak) while preserving 530nm green — the only color shown to not worsen migraine.

Why does this matter? Research by Noseda et al. (2016) showed that migraine photophobia is driven primarily by intrinsically photosensitive retinal ganglion cells (ipRGCs) that peak at 480nm. A broad warm filter reduces some of this light incidentally, but it also removes wavelengths that don't contribute to photophobia while leaving some 480nm light untouched.

Spectral filtering is more precise. It targets the exact wavelengths that research links to migraine pain, while preserving color accuracy across the rest of the spectrum. This is the same principle behind FL-41 tinted lenses, which reduced migraine attacks by 74% in clinical trials — not by making everything orange, but by selectively attenuating the blue-green range. Read the full research.

Side-by-side comparison

f.lux Nox
Approach Color temperature (Kelvin) Spectral curve filtering
Migraine-specific presets 12 research-based presets
FL-41 clinical tint
480nm notch filter
Melanopic suppression metric Real-time %
Narrow-band green mode 520–540nm
Spectral curve modeling 380–780nm (41 points)
Custom presets Limited Full RGB + gamma + temp
Designed for Sleep & circadian rhythm Migraine & photophobia
Platform Mac, Windows, Linux macOS
Price Free $10 (lifetime)

When f.lux is the right choice

f.lux is a great tool that has helped millions of people sleep better. If your primary goal is reducing blue light exposure before bed to improve circadian rhythm, f.lux does that well and it's free. It's available on every platform, has been around for over a decade, and does its job reliably.

Many people use both: f.lux for general evening screen warming, and Nox when they need migraine-level protection. The two tools solve different problems. f.lux makes your screen easier to look at before sleep. Nox filters the specific wavelengths that drive photophobia pain.

When you need Nox instead

If you experience migraines, photophobia, or light sensitivity and find that f.lux's warm filter doesn't provide enough relief, that's because color temperature shifting wasn't designed for this problem. You need wavelength-level precision — targeting the 480nm melanopsin peak, not just making the screen warmer.

Nox gives you 12 presets grounded in photophobia research: FL-41 clinical tint, a 480nm notch filter, narrow-band green (the only wavelength shown to not worsen migraine), and more. Plus a real-time melanopic suppression metric so you can see exactly how much migraine-triggering light your filter removes.

Ready to try wavelength-level migraine filtering?

Nox applies filter profiles based on published research on light sensitivity. It is not a medical device and does not diagnose, treat, or cure any condition. Consult your physician regarding migraine management.