Screen light that works with your body clock, not against it.
CircadianShield walks your display through 11 solar phases, dims in software for PWM sensitive eyes, and scores tonight's light against the clinical guideline.
- Card required. Not charged for 7 days
- macOS and Windows
- Cancel before day 8: no license, no charge
Screens that flicker when they dim can be why your eyes hurt
Many displays dim their backlight with pulse-width modulation, rapid on and off flicker you cannot see but your nervous system can detect. For sensitive eyes that can mean headaches, strain and fatigue by evening.
Core is the entry fix for that computer: keep hardware brightness at 100%, dim in software, start in a few minutes. $27 once, up to 2 computers.
Start 7-day Core trial Read the PWM sensitivity guide
If your job is a screen, this is your day
We read what people actually post about eye strain and screen-wrecked sleep. The same words keep coming up.
My eyes hurt from the monitor all day.
I have no choice, the computer is the job.
Headaches and migraines from desk work.
Blurry vision after a long session.
My brain will not shut off at night.
Screens at night make my insomnia worse.
I completely ruined my circadian rhythm.
Does f.lux even work, or is it placebo?
I can never remember to take breaks.
Source: recurring themes across r/eyestraint, r/Dryeyes, r/migraine, r/insomnia, r/sleep, r/Nightshift, r/optometry, and r/productivity.
Night Shift vs f.lux vs Circadian Shield
See why a simple color tint is not enough for precise evening screen-light control.
| Feature | Circadian Shield | Night Shift | f.lux |
|---|---|---|---|
| Color temperature shift | 11 specialized modes | Basic slider | Automatic |
| Light-exposure standard (CIE S 026) | Full implementation | No | Partial |
| Light dashboard | Light score + trends | No | No |
| Evening light tracking | Post-sunset logs | No | No |
| Soundscapes | 6 solar-synced themes | No | No |
| Per-app control | Per-app profiles | No | Limited |
| Deep enough warmth | Down to 1800K | No (common complaint) | Partial |
| Active development | Active (2026) | Minimal | Stagnant |
| Price | $47 one-time | Free | Free |
Read more: Why Night Shift Isn't Warm Enough (And What Actually Works)
Three steps to calmer screen light
CircadianShield runs quietly in your menu bar and adapts your display automatically.
Install
Download CircadianShield and drag it to your Applications folder. No account required.
Set Your Location
Choose from 130+ city presets or let CircadianShield auto-detect your coordinates for precise solar tracking.
It Just Works
Your display color temperature adjusts automatically as the sun moves. Warm at night, bright in the morning.
Everything your display routine needs
Built on documented light-exposure standards, not just a color tint slider.
Solar-Based Filtering
Tracks your sun's real elevation through 11 twilight phases with smooth sigmoid transitions between 1800K and 6500K.
Morning Boost
A 6500K morning boost synced to civil dawn gives your display a brighter, daytime feel when your day starts.
20-20-20 Break Timer
Every 20 minutes, look at something 20 feet away for 20 seconds. Smart pause during video calls and full-screen apps.
Light Exposure Score
An A, F grade based on your screen-light patterns and timing. Track evening-light exposure and routine changes over time.
Ambient Soundscapes
Six nature themes: ocean, rain, forest, creek, wind, night crickets, generated mathematically on-device and synced to solar phases.
Evening Light Tracking
Tracks post-sunset melanopic exposure and optional morning sunlight logs so you can review screen-light habits over time.
Light Dashboard
Daily scores, 7/30/90-day trend charts, screen-time history, and light-exposure logs stored locally.
11 Display Modes
Auto, Movie, Reading, Coding, Presentation, Gaming, Biohacker, Sunglasses, Dark, Custom, and Disabled. One click in the menu bar.
Per-App Profiles
Color-accurate mode for Photoshop, cinema mode for Netflix, coding mode for Xcode. Each app gets the right filter.
Pro can also hold one fixed warmth for a chosen app, such as a game, on the displays you pick.
PWM Flicker Reduction
Software dimming overlay reduces reliance on hardware backlight dimming for a smoother low-brightness experience.
Smart Automation
Auto-disable in fullscreen, flow detection that defers breaks, inactivity pause, video call detection, and DST smoothing.
On-Device by Design
Solar calculations, settings, light logs, and soundscapes all run locally on your Mac, 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.
Built on melanopic EDI & CIE S 026
CircadianShield uses the CIE S 026:2018 standard to estimate melanopic equivalent daylight illuminance for screen-light tracking. Not just "blue light filtering."
Read the ScienceAvailable on your devices
One price. Everything included.
- Every Pro feature, nothing held back
- macOS and Windows, up to 2 computers
- Free updates, no subscription ever
- 7-day trial on Mac and Windows. Card required. Not charged for 7 days
Cancel before day 8 and you will not be charged. The trial key then stops working. Or buy now for $47.
Before you buy
Is there a free trial?
Yes. A 7-day card-required trial on Mac and Windows. 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 $47 once and that same key becomes lifetime. Pay now is still at /buy.
How is Circadian Shield different from f.lux or Night Shift?
f.lux and Night Shift apply a basic color temperature tint. Circadian Shield uses CIE S 026 melanopic EDI calculations for screen-light management, plus 11 display modes, a local dashboard with light-exposure scoring, light debt tracking, ambient soundscapes, and PWM flicker protection.
What is light debt?
Evening light estimates post-sunset melanopic light exposure from screens. Circadian Shield helps you track evening exposure patterns and compare them with optional morning light logs.
Does Circadian Shield work on Apple Silicon Macs?
Yes. Circadian Shield is fully optimized for Apple Silicon (M1, M2, M3, M4) and compatible with macOS 14 Sonoma and macOS 15 Sequoia.
More questions? Read the full FAQ.
Tonight's screen light shapes tomorrow morning
Set it up in two minutes and let your display follow the sun from now on. Start a 7-day Pro trial. Cancel before day 8 and you will not be charged, and the key stops working.
macOS and Windows. Or buy now for $47.