Every feature your eyes need
CircadianShield goes far beyond a simple color tint. Here is everything it does to protect your circadian rhythm.
Solar-Based Color Temperature
Unlike simple timers, CircadianShield calculates the sun's exact elevation angle at your location in real time. It maps solar position to display color temperature using smooth sigmoid transitions, no jarring shifts.
- Tracks 11 distinct twilight phases from astronomical dawn to astronomical dusk
- Smooth sigmoid curve transitions (no abrupt color changes)
- Full range from 1800K deep amber to 6500K daylight white
- Adjusts differently for summer and winter day lengths
- Works offline after initial location setup
Morning Boost
Light exposure within the first hour of waking is the single most powerful signal to anchor your circadian clock. CircadianShield's Morning Boost delivers a timed 6500K pulse synced to civil dawn to suppress residual melatonin and kick-start cortisol.
- Activates automatically at civil dawn for your location
- 6500K blue-enriched white for maximum alertness
- Configurable duration (15, 30, or 60 minutes)
- Gradual ramp-down to avoid sharp transitions
- Can be deferred if you wake before dawn
20-20-20 Break Timer
The 20-20-20 rule is recommended by the American Academy of Ophthalmology: every 20 minutes, look at something 20 feet away for 20 seconds. CircadianShield implements this with smart awareness of your context. Learn how the break timer works or see the shorter overview on our 20-20-20 rule app page.
- Gentle, non-intrusive break reminders
- Automatically pauses during video calls (Zoom, Meet, Teams, FaceTime)
- Pauses in full-screen mode (presentations, movies)
- Tracks break compliance in your health score
- Configurable intervals (20, 30, or 45 minutes)
Circadian Health Score
Your daily A, F circadian grade measures how well your light exposure aligns with your biological clock. Track improvements over days and weeks to build healthier habits.
- A, F letter grade updated in real time
- Factors in: evening blue light, morning exposure, break compliance, override frequency
- Light debt tracking, see how much circadian disruption has accumulated
- Weekly and monthly trend charts in the menu bar dashboard
- Actionable tips to improve your score
Per-App Profiles
Not every app needs the same treatment. CircadianShield lets you assign display profiles to individual applications so your creative work stays color-accurate while everything else stays circadian-safe.
- Color Accurate, Photoshop, Lightroom, Figma (filter disabled or minimal)
- Cinema, Netflix, Disney+, VLC (warm but preserves contrast)
- Coding, Xcode, VS Code, Terminal (reduced blue, high contrast)
- Reading, Safari, Preview, Kindle (deep warm, low brightness)
- Create custom profiles for any application
Fixed Warmth App Profiles PRO
Pick an app, such as a game, and give it one warmth, anywhere from 1,800 K to 6,500 K, on the displays you choose. While that app is in front, those displays hold that warmth with no day or night schedule. Your other displays keep following the sun, and when you leave the app everything eases back to normal in about a second.
- Choose all displays or specific ones for each app
- If the app fills a display, full screen or maximized, that display keeps its warmth even while you click into apps on another display
- Close and reopen the app and it picks the warmth back up by itself
- Works in full screen even with the auto-disable for fullscreen apps setting on
- Warmth applies to the whole display, not a single window
- On Mac and Windows. On Mac, the Cinema, Coding and Reading profiles also change warmth while their app is in front
PWM Flicker Protection
Many displays dim the backlight using pulse-width modulation (PWM), rapid on/off flickering invisible to the naked eye but detectable by your nervous system. This causes headaches, eye strain, and fatigue. CircadianShield offers a software dimming overlay that reduces brightness without PWM. If you are comparing setups, start with our guides to PWM displays, PWM monitors, and PWM sensitivity.
- Software overlay dims the screen without hardware flicker
- Particularly helpful for OLED and low-brightness LCD panels
- Adjustable overlay opacity
- Combines with color temperature for complete eye protection
130+ City Presets
Get accurate solar data without sharing your precise GPS coordinates. Choose from 130+ built-in city presets covering every time zone, or enter custom coordinates.
- Major cities across all continents pre-loaded
- Auto-detect location option (one-time, not continuous tracking)
- Custom latitude/longitude input
- Travel mode, quickly switch when you change cities
- All calculations happen on-device, never sent to a server
11 Display Modes
Quick-switch between optimized display modes from the menu bar. Each mode adjusts color temperature, brightness overlay, and break timer behavior.
- Auto, Full solar tracking (default)
- Movie, Warmed whites, preserved contrast, auto-reverts after 2.5 hours
- Reading, Deep amber, reduced brightness for long text sessions
- Presentation, Temporarily disables filtering for accurate slides
- Coding, Moderate warmth with high text contrast
- Gaming, Full brightness, breaks paused so you stay in the zone PRO
- Biohacker, Aggressive dynamic curve that maximizes circadian benefit PRO
- Sunglasses, 2200K deep warmth + 60% dimming for light-sensitive users PRO
- Dark, 1800K candlelight + 85% dimming for extreme night use PRO
- Custom, Set your own Kelvin and dim level for any situation PRO
- Disabled, Turns off all filtering while keeping the app running
Health Dashboard PRO
A full circadian health dashboard with daily scores, trend charts, and actionable insights. Track how your light habits improve over days, weeks, and months.
- Daily circadian health score (0 to 100) with A, F letter grade
- Three scoring components: exposure quality (40pts), break compliance (30pts), protocol adherence (30pts)
- 7-day, 30-day, and 90-day trend charts for score, screen time, and light debt
- Sleep quality tracking (daily 1 to 5 star self-rating)
- Sleep-on-low-debt vs sleep-on-high-debt correlation insights
- Up to 365 days of health history stored locally
Light Debt Tracking PRO
Light debt measures how much high-melanopic light your eyes absorbed after your biological dim-light window began. Like sleep debt, it accumulates, and CircadianShield tracks it so you can pay it back.
- Accumulates melanopic EDI exposure after your estimated DLMO (dim light melatonin onset)
- Four debt levels: Low, Medium, High, Critical, each with specific recovery advice
- Recovery via morning sunlight logging (quick-log 10, 15, or 30 minutes)
- Overnight sleep recovery (60 to 85% reduction based on sleep duration)
- Daytime natural decay (2 points per hour)
- Color-coded status in menu bar and dashboard
Morning Coach PRO
During your morning window (wake time to 3 hours after), the Morning Coach card guides you toward your daily light target with contextual tips based on your current light debt.
- Progress ring showing actual vs 30-minute morning sunlight target
- Quick-log buttons: +10, +15, +30 minutes of outdoor sunlight
- Light debt status with color-coded severity indicator
- Contextual coaching tips that adapt to your current debt level
- Appears only during the morning window, never in the way
Time Machine Preview
Scrub through a full 24-hour timeline to see exactly what your display will look like at any time of day. Useful for understanding the solar-driven transitions before they happen.
- Drag a slider from 00:00 to 23:59 in 15-minute increments
- Real-time preview of color temperature, phase name, and solar elevation
- Color swatch with RGB values at each point
- Melanopic factor display so you can see the science behind each transition
Ambient Soundscapes PRO
Six nature-inspired soundscape themes generated mathematically on-device, no downloads, no streaming, no cloud. The active soundscape transitions automatically as the sun moves through its phases.
- Ocean Waves, Rainfall, Forest, Creek, Wind, Night Crickets
- Four circadian groups (Night, Dawn, Day, Dusk) matched to solar phases
- Pure math synthesis at 44,100 Hz, zero external audio files
- Seamless crossfade between themes as the sun moves
- Adjustable volume with instant response
- No competitor offers circadian-synced ambient audio
Spotlight & Vignette Dimming PRO
Two advanced screen dimming modes that reduce peripheral light exposure without hiding your work area.
- Spotlight Dimming, Radial gradient keeps a bright circle around your cursor, darkens everything else
- Vignette Mode, Darkens screen edges (40 to 60% reduction) while keeping the center bright
- Customizable radius and opacity for both modes
- Follows mouse movement across displays
- Works independently or combined with color temperature filtering
Screen Effects PRO
Additional display transformation effects for specific needs.
- Grayscale, Removes all color saturation to reduce visual stimulation
- Invert, Inverts all screen colors for accessibility or preference
- Applies above the color overlay layer
- Can be toggled per-display or globally
Smart Automation
CircadianShield adapts to how you work. It knows when to step aside and when to stay active.
- Auto-Disable in Fullscreen, Automatically pauses when you enter full-screen mode
- Auto-Disable by App, Detects color-accurate apps and pauses filtering
- Movie Mode Auto-Timer, Automatically reverts to your previous mode after 2.5 hours
- Inactivity Pause, Pauses filtering when you step away (configurable threshold) PRO
- Flow Detection, Defers break reminders when you are in deep focus PRO
- Auto Dark Mode, Automatically switches macOS to dark appearance at sunset
- DST Smoothing, Gradual schedule shift during daylight saving transitions
- Video Call Detection, Pauses breaks during Zoom, Teams, FaceTime, Slack, and more
Flexible Scheduling
Solar tracking works for most people, but CircadianShield also supports custom schedules for shift workers, travelers, and extreme latitudes.
- Separate wake and sleep times for weekdays
- Weekend Schedule, Different wake/sleep times for Saturday and Sunday PRO
- Manual Night Schedule, Override solar timing entirely with custom start/end hours
- DLMO (dim light melatonin onset) estimation based on your sleep time
- Backwards alarm clock: "X hours until bedtime"
- "If you sleep now" calculator with estimated wake time
Per-Display Control PRO
Run different color temperature and brightness settings on each connected monitor. Your laptop screen can be warm for nighttime reading while your external display stays neutral for reference material.
- Independent Kelvin and brightness per monitor
- Enable or disable filtering per display
- Automatic detection when monitors are connected or disconnected
- Works with external monitors, ultrawides, and projectors
Keyboard Shortcuts PRO
Control CircadianShield without touching the menu bar. Every major action has a configurable global hotkey.
- 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
- Emergency reset (Ctrl+Option+Escape) to restore all defaults
- Optional keyboard blocking during breaks to enforce rest
Circadian Profiles PRO
Save named sets of all your settings, wake/sleep times, Kelvin range, Morning Boost, transition speed, and switch between them instantly.
- Create profiles like "Work", "Weekend", "Travel", "Night Shift"
- Each profile stores wake/sleep times, Kelvin range, Morning Boost toggle, and transition speed
- Switch profiles from the menu bar or via keyboard shortcut
- Export and import profiles between machines
On-Device & Private
CircadianShield's screen filtering and health scoring run entirely on your Mac. No cloud accounts required, and no screen content or personal data ever leaves your machine. The app sends optional anonymous usage and technical diagnostics that you can switch off in Settings.
- All solar calculations performed locally using astronomical algorithms
- Health scores, light debt, and history stored only on your device
- Soundscapes generated mathematically, no audio streaming
- Optional anonymous usage statistics only, with an off switch in Settings, no personal profiling or ad SDKs
- Settings export/import for backup without any cloud dependency
Ready to protect your circadian rhythm?
Download CircadianShield and let the sun drive your display.
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