f.lux pioneered color temperature shifting — but it stopped there
f.lux was groundbreaking when it launched. But it has not kept pace with circadian science. It still offers a single color temperature slider with basic sunrise/sunset scheduling. There is no health tracking, no light debt concept, no melanopic EDI calculations, and no way to know if the filter is actually helping your circadian rhythm.
Your blue light filter should do more than tint your screen
Circadian Shield uses the CIE S 026:2018 standard to calculate melanopic equivalent daylight illuminance — the metric that actually predicts circadian impact. It tracks your light exposure across the day, grades your circadian health, and shows you exactly how much “light debt” you accumulate from late-night screen use.
11 modes for how you actually work
Coding at midnight needs different filtering than watching a movie. f.lux applies one setting globally. Circadian Shield gives you 11 purpose-built modes — Auto, Movie, Reading, Coding, Presentation, Gaming, Biohacker, Sunglasses, Dark, Custom, and Disabled — that you can assign per-app or switch with a click.
See the difference in your health dashboard
f.lux gives you no feedback on whether its filter is working. Circadian Shield shows you daily circadian scores, 7/30/90-day trends, sleep quality correlation, and light debt recovery. You can actually see the impact of better light habits.