Screen Time Before Bed: A Mac Evening Routine by Kelvin

Last Updated: September 2026

Screen time before bed can push sleep later, and the clearest evidence is about bright, blue-rich light in the last hours of the evening. In a controlled study at Brigham and Women's Hospital, people who read on a light-emitting eReader before bed took longer to fall asleep, felt less sleepy in the evening, secreted less melatonin and were less alert the next morning than when they read a printed book. That is the problem. The good news is that on a Mac most of the light side of it is adjustable, one setting at a time, in the two hours before you sleep.

This guide turns screen time before bed into a routine: what to change at two hours out, at one hour out, and at lights-out, with a colour temperature in kelvin for each step. No study tested this ladder. It is a practical plan that follows what the evidence points at: less short-wavelength light, dimmer, earlier. If you want the biology of why blue light matters at night, that is covered in what your Mac display does to your sleep. Here we stay practical.

What does screen time before bed actually do?

Evening screen time does two separate things, and only one of them is about colour. The first is light: a bright, cool-white screen close to your face tells your internal clock it is still daytime, which can delay melatonin and push sleep later. The second is arousal: an email, a game or a feed keeps your mind switched on regardless of what colour the pixels are.

The light half is well studied. Anne-Marie Chang, Charles Czeisler and colleagues published the eReader comparison in PNAS in 2015 (Chang 2015, PMID 25535358). Same people, same bedtime, one variable changed: a light-emitting device or a paper book. On the device, their circadian clocks ran later and their melatonin was suppressed. Four years earlier, Joshua Gooley and a Harvard team reported in the Journal of Clinical Endocrinology and Metabolism that ordinary room light in the hours before bed, compared with dim light, delayed the evening rise of melatonin and shortened how long it was produced (Gooley 2011, PMID 21193540). Notice that Gooley's exposure was room light, not a screen. Your overhead lights count too.

The arousal half is the part no display setting can touch, and that limit belongs at the top of any guide like this one. A warm screen showing a stressful inbox is still a stressful inbox. Warmth addresses the light, and the routine below treats content as its own step.

Screen time before bed is also normal. In a November 2021 survey for the National Sleep Foundation's 2022 Sleep in America Poll, 58% of US adults said they often looked at screens in the hour before bed or in bed. If that describes you, you are in the majority, and the useful question is what the screen is doing during that hour.

The evening routine, step by step

Everything below uses one number: colour temperature in kelvin (K). Lower numbers mean warmer, redder light with less of the short-wavelength blue that the clock responds to most. Your Mac's default white is about 6500 K, the same reference white as average daylight. Sundown's menu bar slider runs from 6500 K down to 500 K in 100 K steps, so each setting below is a position you can actually find. If kelvin is new to you, colour temperature explained walks through what the numbers mean.

These are settings for how the screen looks. They are not a promise of how you will sleep, and no study has tested Sundown itself.

Two hours before bed: 2700 K and lower brightness

Set the display to about 2700 K and bring the brightness down as far as you can while still reading comfortably. At 2700 K a white page looks like paper under a bedside lamp: whites turn gold, blues go muddy, and text stays perfectly readable, so this is the setting for real work you still have to finish. It is also roughly where Night Shift stops, which is why Night Shift is a reasonable start and a poor finish.

Then look up. Gooley's result was about room light, so dim the overhead lights and switch to lamps if you can. A warm screen in a brightly lit kitchen is only half the change.

One hour before bed: 1900 K, then 1200 K

Drop to about 1900 K, the orange of a candle flame. Photos lose their colour accuracy here, which is fine because you should not be editing photos at this hour. If you are still on the screen after half an hour, go further, to 1200 K, where the display turns a deep amber and blues mostly disappear.

This is also the content step. Stop starting new work. Finishing a reply is fine; opening a new project is how an hour becomes three. Reading, a slow video or a list for tomorrow all suit a 1200 K screen better than a spreadsheet does.

Lights-out: 500 K, or close the lid

If you are still using the Mac at lights-out, set it to 500 K. At 500 K there is no lamp to compare it to; the screen shows a deep red, the white of a page becomes dark red, and colours are gone. It is readable, and it is the setting to use for the last message or the alarm check. Our guide to a red screen filter for sleep covers when a fully red screen is worth it.

The better option is to close the lid. No setting on any screen beats not looking at one.

The routine at a glance

Sundown has a custom schedule if you want the steps to follow a set time, but you can do this whole routine by hand from the menu bar in a few seconds a night, and starting by hand is a good way to find the settings you actually like.

What does the research on blocking evening blue light show?

The strongest direct evidence comes from glasses, not screens, and that difference matters. The study most often quoted is Ostrin, Abbott and Queener at the University of Houston College of Optometry (PMID 28656675). Ostrin et al. (2017) found blue-blocking lenses raised nocturnal melatonin ~58% in healthy adults, who also slept ~24 minutes longer. That result came from two weeks of wearing short-wavelength-blocking amber glasses in the evening. It was a before-and-after design without a placebo group, and it tested lenses, not display software.

The reasoning that carries it to a Mac is simple: glasses and a warm screen both reduce the short-wavelength light reaching your eyes. We think that transfer is reasonable, and the Sundown science page says plainly that it is an inference, not a finding. Every study above is listed there with what it did not test.

If you have insomnia symptoms

One trial looked specifically at people with insomnia. Ari Shechter and colleagues at Columbia University had fourteen adults with insomnia symptoms wear amber lenses or clear placebo lenses for the two hours before bed, for a week each, in a randomised crossover design (Shechter 2018, PMID 29101797). Scores on an insomnia rating scale improved with the amber lenses, as did reported sleep time and sleep quality. Most of those measures were self-reported, the group was small, and again it was a lens study.

So a warm, dim evening screen is a sensible thing to try, and it is cheap to try. It is not a treatment. If you have had trouble sleeping most nights for weeks, talk to a doctor or a sleep clinician. The usual first recommendation for persistent insomnia is a structured programme called cognitive behavioural therapy for insomnia (CBT-I), and it works on the arousal and habit side that no screen setting can reach.

What helps less than people think

Night Shift left where it is. Night Shift takes the screen from 6500 K to roughly 2700 K, which cuts the blue channel and is the first step of this routine, not the last one. It does not change brightness.

A warm screen at full brightness. Colour and brightness work together. Heo and colleagues at Samsung Medical Center had healthy adults play smartphone games in the evening on a normal phone and on one with blue light suppressed, in a double-blind crossover (Heo 2017, PMID 28017916). Some sleepiness and mood measures differed between the phones, but the difference in serum melatonin was not statistically significant. We cite it because leaving it out would misrepresent the field: reducing blue alone, on a bright screen, is not a guaranteed effect. That is why this routine lowers brightness and room light alongside kelvin.

Dark mode on its own. Dark mode lowers how much light the screen emits but leaves the white point where it was. We measured the macOS system colours in does dark mode reduce blue light.

Questions people ask about screen time before bed

How long before bed should I stop using screens?

No study has set a cut-off for Mac use. The two-hour start in this routine is a practical choice, borrowed loosely from the insomnia trial above, which tested amber lenses worn for two hours before bed rather than a warmer display. If stopping completely is not realistic, warming and dimming the screen through the evening and closing the lid at lights-out means less light, and less blue-rich light, from the display.

Is a warm screen as good as no screen?

No. A screen at 500 K still gives off light, and the content on it still keeps your mind busy. A warm screen gives off less short-wavelength light than a cool one, and a closed lid gives off none.

Does dark mode help sleep?

Our dark mode measurement found that dark mode lowers the relative luminance of what a Mac shows, so the screen gives off less light overall. It does not change the colour temperature of the white that remains, and no trial has tested dark mode for sleep. For evening use, pair it with a low kelvin setting and lower brightness.

If you want to change your screen time before bed starting tonight, Sundown puts the kelvin slider in your menu bar, from 6500 K down to 500 K. Start at 2700 K two hours before bed and see how far down you like it. There is a 7-day free trial on monthly and annual plans: Start your 7-day free trial at trysundown.com.