Abendrot app icon - a golden sun setting into a calm sea beneath a warm twilight sky.

Abendrot

Download for macOS GitHub

The macOS app for your circadian rhythm

Grounded in peer-reviewed light research, Abendrot warms your entire workspace around sunset because staring at bright blue light at night is suboptimal.[1,4-6,8]

Abendrot menu bar controls showing a 2600 Kelvin readout, Sunset and Manual modes, and the Reveal True Color shortcut.

Menu bar control

Adjust warmth, see the estimated blue-channel reduction, and switch between Sunset and Manual without opening Settings.

Abendrot Settings showing connected displays with Automatic, Screen tint, and Hardware control options.

Tune each display

See each connected display and choose Automatic, Screen tint, or Hardware control when available.

Sunset mode

Warms automatically around your local sunset, using your time zone or a city you choose.

Cozy mode

Extend maximum warmth beyond the everyday range for the app’s warmest setting.

Reveal True Color

Hold or toggle a global shortcut to temporarily return your screen to true color.

Private by design

No account, analytics, or usage telemetry. Your settings stay on your Mac.

The science

At night, you need to reduce your blue light exposure.

Abendrot targets the root cause of sleep disruption by minimizing the specific short-wavelength, melanopic light (blue/cyan) that tricks your body clock into thinking it's still daytime.[1,4-6]

Your body's internal clock processes light differently than your eyes do.1 The real goal is to reduce your exposure to sleep-disrupting blue and cyan light (short-wavelength, melanopic light) in the evening, aligning with your natural circadian rhythm.[4-6]

1 Your clock reads blue differently than your eyes do.

Rods and cones make the picture. A separate melanopsin system helps tell the brain whether it is day or night, and it is most sensitive around blue-cyan light near 480–490 nm.12 That is the band screen warming is meant to attenuate first.4

2 Warmth is a spectral edit, not a sleep claim.

Lowering Kelvin is useful only because it changes the spectrum: less energy in the short wavelengths the melanopic system weights heavily.4 Abendrot’s everyday warm range is built around that input-side change: remove blue first, then leave the rest of the evening tradeoff to your eyes and the slider.

3 Melanopic load is the better evening word than brightness.

In a controlled display study, the melanopic content of evening screen light mattered even when ordinary brightness and color appearance were separated from it.5 That is why Abendrot talks about blue-rich light, not just whether the screen looks bright or beige.

4 Dim still matters.

Warming changes color. Dose still depends on intensity. Expert consensus frames evening light in melanopic EDI at the eye, and nocturnal light response rises steeply with brightness.68 The honest habit is warm and dim, not warm and glaring.

5 There is no perfect setting for everyone.

People vary by more than fifty-fold in sensitivity to evening light, so a single universal number would be fake precision.7 Abendrot gives you an adjustable evening nudge, not a clinical tool or an outcome guarantee.

Illustrative CIE S 026 melanopic action spectrum A smooth sensitivity curve peaks near 490 nanometres, then falls toward the red end of the visible spectrum. A warm shaded band marks the short wavelengths that screen warming attenuates first. short wavelengths attenuated first peak ≈ 490 nm 400 490 530 600 700 nm
Illustrative - CIE S 026:2018 melanopic action spectrum, not a measured output of Abendrot. The curve shows why blue-cyan light counts heavily for circadian input, while orange and red sit near the low-sensitivity end of the spectrum.

How it compares

How Abendrot compares to Night Shift and f.lux

Night Shift is built into macOS; f.lux is a separate third-party app. Abendrot combines an everyday 1900 K range with an optional near-red Cozy endpoint, per-display hardware controls on compatible monitors, and software fallbacks.

Open & private

Night Shift

Proprietary macOS feature1

f.lux

Proprietary app2

Abendrot

Open source (MIT-licensed); the Mac app sends no analytics or usage telemetry3

Warmth & blue reduction

Night Shift

No published Kelvin endpoint or endpoint spectrum; warmer settings show more yellow and less blue1

f.lux

Ember preset: 1200 K; warm presets reduce blue, with physical output varying by display2

Abendrot

Everyday warmth, plus optional near-red Cozy mode for stronger blue reduction at night4

Resource footprint

Night Shift

Built into macOS Displays settings1

f.lux

Separate macOS menu-bar app; its developer has documented polling to recover color profiles and external-display changes2

Abendrot

Native and event-driven. In one matched Mac test, Abendrot used 24% less median memory than f.lux4

Scriptable & AI-controllable

Night Shift

Shortcuts and Siri can toggle it; no public CLI or live state output1

f.lux

No documented Mac CLI or public screen-control API2

Abendrot

Built-in CLI lets you control Abendrot with scripts and AI tools—adjust warmth or trigger Reveal4

External & multiple displays

Night Shift

External-display performance depends on the display1

f.lux

Supports multiple displays; compatibility varies by system and display path2

Abendrot

Adapts to each display and automatically restores warmth when monitors connect or change4

References

Melanopic Evidence

  1. Berson DM, Dunn FA, Takao M (2002). Phototransduction by retinal ganglion cells that set the circadian clock. Science. doi.org/10.1126/science.1067262
  2. Brainard GC, et al. (2001). Action spectrum for melatonin regulation in humans. The Journal of Neuroscience. doi.org/10.1523/JNEUROSCI.21-16-06405.2001
  3. Thapan K, Arendt J, Skene DJ (2001). An action spectrum for melatonin suppression. The Journal of Physiology. doi.org/10.1111/j.1469-7793.2001.t01-1-00261.x
  4. CIE (2018). CIE S 026/E:2018 - System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light. CIE International Standard. doi.org/10.25039/S026.2018
  5. Schoellhorn I, et al. (2023). Melanopic irradiance defines the impact of evening display light on sleep latency, melatonin and alertness. Communications Biology. doi.org/10.1038/s42003-023-04598-4
  6. Brown TM, et al. (2022). Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLoS Biology. doi.org/10.1371/journal.pbio.3001571
  7. Phillips AJK, et al. (2019). High sensitivity and interindividual variability in the response of the human circadian system to evening light. PNAS. doi.org/10.1073/pnas.1901824116
  8. Zeitzer JM, et al. (2000). Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. The Journal of Physiology. doi.org/10.1111/j.1469-7793.2000.00695.x
  1. Apple’s current Night Shift documentation places Night Shift in System Settings > Displays, publishes no Kelvin endpoint, says warmer settings show more yellow and less blue, and says external-display performance depends on the display’s characteristics. Apple also documents Control Center and Siri controls and a Set Night Shift action in Shortcuts; its current documentation publishes no CLI or live machine-readable state output. macOS is distributed under Apple’s software license agreements.
  2. f.lux lists Ember at 1200 K, documents its separate macOS process, and distributes under a proprietary EULA. Its display behavior can vary with the system and display path, and its developer documents polling to recover color profiles and external-display changes. The current Mac documentation publishes no bundled CLI. Its LAN API is for programmable lights, not screen control; the official forum records longstanding requests for command-line control and says an inbound control API was not shipping.
  3. Abendrot is open source under the MIT license. Its privacy page documents that the Mac app sends no analytics or usage telemetry.
  4. In the audited Abendrot source, the everyday range stops at 1900 K; Cozy mode extends to a near-red software endpoint. The core transform sets the digital blue gain to zero at 1900 K, but physical output varies by display and the overlay fallback is a tint with documented limits. DDC requires compatible hardware and opt-in, with gamma and overlay fallback paths, the app runs with no privileged helper, WarmthKit coalesces display and wake events, and the fallback overlay redraws only when its gain changes. In a July 27, 2026 same-machine spot test on a 24 GB M5 MacBook Air running macOS 26.5, f.lux 42.2 and Abendrot 0.1.0 were each active at 1900 K on the built-in display and an LG UltraFine. After a 60-second warm-up, 90 process samples at two-second intervals gave both apps 0.0% median CPU and 0.1% p95 CPU; median RSS was 61.94 MB for Abendrot and 81.69 MB for f.lux. One user menu interaction caused a late Abendrot CPU/RSS outlier; the medians above use the full 90-sample run. These are single-machine spot-test results, not a universal performance guarantee. Abendrot’s documented command-line interface reads live state as JSON, changes warmth, triggers Reveal, and supports scriptable exit codes.