Frequently Asked Questions

CircadianShield is a macOS and iOS app that adjusts your display's color temperature based on the sun's real position at your location. It transitions smoothly from 6500K daylight white to 1800K deep amber to protect your circadian rhythm, improve sleep quality, and reduce digital eye strain. Everything runs on-device with no data sent to the cloud.

Night Shift uses a simple timer with a basic warm tint and no granularity. It does not track solar position, offers no health scoring, and cannot be customized per app.

f.lux uses sunrise/sunset times and offers more customization than Night Shift, but still uses a simpler solar model. CircadianShield tracks the sun's actual elevation angle through 11 distinct twilight phases, uses melanopic EDI calculations based on the CIE S 026:2018 standard, and includes features like Morning Boost, per-app profiles, a circadian health score (A-F), break timer with smart context awareness, and PWM flicker protection.

Yes. CircadianShield applies a software color overlay that works with any display connected to your Mac, including external monitors, ultrawide displays, and projectors. Each connected display receives the same filtering. Per-app profiles work across all connected screens.

CircadianShield includes per-app profiles specifically for this concern. You can set color-critical apps like Photoshop, Lightroom, Figma, and Final Cut Pro to "Color Accurate" mode, which disables or minimizes the filter for that app only. You can also use the Presentation display mode to temporarily disable all filtering system-wide with a single click in the menu bar.

Only if you choose auto-detect for your location (a one-time lookup). After your coordinates are stored, all solar position calculations happen entirely on-device using standard astronomical algorithms. You can also select from 130+ built-in city presets with no internet connection required at all. CircadianShield never phones home, collects analytics, or sends data to any server.

Minimal. CircadianShield recalculates solar position once per minute and applies a lightweight color overlay. CPU usage is typically under 0.5%, and battery impact is negligible. The app uses less energy than most menu bar utilities. The PWM software dimming overlay, if enabled, adds a similarly negligible overhead.

CircadianShield requires macOS 14.0 (Sonoma) or later. It runs natively on both Apple Silicon (M1, M2, M3, M4) and Intel Macs. The app is fully optimized for Apple Silicon and uses minimal system resources.

An iOS companion app is currently in development and will be available on the App Store soon. Due to iOS platform limitations, the iOS version focuses on circadian health tracking, break reminders, and Morning Boost notifications rather than direct display color manipulation. Sign up for updates on the download page.

Your circadian health score is an A-F grade calculated daily based on four factors:

1. Evening light discipline — How much high-melanopic light your display emitted after sunset.
2. Morning exposure — Whether you received adequate bright light in the first hour after waking.
3. Break compliance — How consistently you followed 20-20-20 break reminders.
4. Override frequency — How often you manually disabled or bypassed CircadianShield's recommendations.

The score also tracks "light debt" — accumulated circadian disruption over time. Weekly and monthly trends are visible in the menu bar dashboard.

Yes. CircadianShield supports per-app profiles. You can assign any application a specific display profile (Color Accurate, Cinema, Coding, Reading, or a custom profile). The Color Accurate profile disables filtering entirely for that app. You can also create a fully custom profile with your own color temperature and brightness overlay settings. Profiles switch automatically when you focus the relevant app.