Frequently Asked Questions

CircadianShield is not a blue-light filter. It is an eye-health and circadian operating layer for screens: a macOS and Windows app that adjusts your display's color temperature based on the sun's real position, tracks screen-light habits, supports breaks, and produces health reports. Screen filtering and health scoring run on-device, and no screen content or personal data ever leaves your machine. The app sends only optional anonymous usage and technical diagnostics that you can switch off in Settings.

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. A 7-day card-required trial on Mac and Windows for Core or Pro. You are not charged for 7 days. Cancel before day 8 and the trial key stops working and you do not keep a licensed copy. If you do not cancel, you are charged once ($27 Core or $47 Pro) and that same key becomes lifetime. Pay-now is still available at /buy and /buy-core. You can activate or deactivate your license from the Account tab in Settings.

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. Your location, health data, and screen content never leave your machine. The app sends only optional anonymous usage and technical diagnostics that you can switch off in Settings.

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

Yes. Pro includes per-display control: independent color temperature and brightness settings for each monitor. Filtering automatically re-applies when monitors are connected or disconnected.

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.

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.

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.

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.

Yes, with Pro. Fixed warmth app profiles let you pick an app, choose one warmth from 1,800 K to 6,500 K, and choose which displays it applies to. While that app is in front, those displays hold that warmth with no day or night schedule, and your other displays keep following the sun. If the app fills a display, full screen or maximized, that display keeps its warmth even while you click into apps on another display. It works in full screen even with the auto-disable for fullscreen apps setting on, and leaving the app eases displays back to normal within about a second. Warmth applies to the whole display, not a single window. It is available on Mac and Windows.

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.

Light debt measures how much high-melanopic light your eyes absorbed after your dim light melatonin onset (DLMO) window began. Think of it like sleep debt, it accumulates when you use bright screens late at night.

CircadianShield tracks four debt levels: Low (great job), Medium (consider 15 min extra morning sunlight), High (extended morning protocol suggested), and Critical (screen-free evening + sunrise walk recommended). You recover by logging morning sunlight exposure, sleeping well, and natural daytime decay. This is a Pro feature.

CircadianShield Pro includes six nature-inspired soundscape themes: Ocean Waves, Rainfall, Forest, Creek, Wind, and Night Crickets. They transition automatically as the sun moves through its phases, calming night sounds after dark, gentle dawn ambience in the morning, brighter tones during the day.

All audio is generated mathematically on your Mac or PC at 44,100 Hz with seamless crossfading. No audio files are downloaded or streamed. No competitor offers circadian-synced ambient audio.

Yes. Use Manual Night Schedule to override solar-based timing entirely with your own custom start and end hours. This is ideal for nurses, doctors, factory workers, and anyone on non-standard hours.

You can also create separate Circadian Profiles (Pro) for day shifts and night shifts and switch between them from the menu bar or a keyboard shortcut.

Pro includes 10 configurable global hotkeys: toggle filtering on/off, cycle through display modes, adjust Kelvin up/down in fine (+100K) or coarse (+500K) steps, toggle PWM protection, trigger an immediate break, and open settings.

There is also an Emergency Reset shortcut (Ctrl+Option+Escape) that restores all settings to defaults, useful if you accidentally set extreme values.