Features

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.

  • 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

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.

  • 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

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, no break interruptions
  • Reading — Deep amber, reduced brightness for long text sessions
  • Presentation — Temporarily disables filtering for accurate slides
  • Coding — Moderate warmth with high text contrast

Ready to protect your circadian rhythm?

Download CircadianShield and let the sun drive your display.

Download for macOS