Two Windows Light Protocol
A two-part daily light hygiene protocol: get early outdoor morning light to anchor the circadian clock, and keep evening indoor light at or below 10 lux in the three hours before sleep to protect melatonin. A dimmer switch is offered as the simple practical tool for the evening half.
Assembled by Cited from Matt Walker's recorded recommendations across multiple sources. It is not an ordered program and was not created or endorsed by them — it's our grouping of what they've said on the record.
Components
3-
In a protocol
Get outside into real outdoor light as early as practical after waking to anchor the circadian clock; duration is less important than simply receiving the signal.
“Simply get outside, get real light, get it early.
TM▶ 23:00DosageBrief outdoor light exposure early in the morning, before first 2-3 hours indoors; even overcast days sufficeCaveatsIndoor lighting generally cannot match outdoor light intensityCertaintyexplicitstrong endorsementMorning window: outdoor light as early as practical after waking. -
In a protocol
Keep indoor light at or below 10 lux in the three hours before sleep to avoid suppressing melatonin.
“keep indoor light at or below 10 lux
TM▶ 23:30Dosage≤10 lux for 3 hours before intended sleep; e.g., a single low-wattage lampCaveatsNot comfortable for typical tasks like cooking or working; requires deliberate effortCertaintyexplicitstrong endorsementEvening window: ≤10 lux for the 3 hours before sleep. -
In a protocol
A simple dimmer switch combined with the habit of using it is sufficient to achieve appropriate evening light levels.
“a dimmer switch and the habit of using it will take you most of the way there
TM▶ 24:30CertaintyexplicitrecommendationPractical implementation tool for achieving the evening dim-light target.
How this protocol has evolved
Matt notes the screen story has evolved — he previously emphasized blue light from screens suppressing melatonin, but updated evidence from Gradisar reframes screen harm as primarily behavioral (keeping you up) rather than biological, shifting emphasis to room light instead.