Night Shift on Mac: How to Turn It On, and What It Won't Fix

Night Shift is the most-searched eye setting on macOS, and the most misunderstood. It is a real feature that does a real thing. It is also sold — mostly by other people, not by Apple — as a treatment for tired eyes, and it is not that.

This is what it does, where to find it, and what to use instead when your eyes hurt at 4pm rather than at 11pm.

What Night Shift actually does

Night Shift shifts the white point of your display toward the warm end of the spectrum. White stops being blue-white and becomes amber-white, as though the screen were lit by a filament bulb instead of daylight. Every colour on screen moves with it.

That is the entire feature. It does not dim the screen. It does not change contrast. It does not change what your apps look like. It removes short-wavelength (blue) output by rebalancing the panel, and nothing else.

The reason it exists is circadian, not ocular. Short-wavelength light in the evening suppresses melatonin and delays sleep onset. That mechanism is well established. Night Shift is Apple's attempt to reduce the evening dose.

How to turn it on

macOS Ventura, Sonoma and later

1. Open System Settings → Displays
2. Click Night Shift… at the bottom right
3. Set Schedule to Sunset to Sunrise or Custom
4. Drag Colour Temperature between Less Warm and More Warm

The same panel has a manual switch: Turn On Until Tomorrow, or Turn On Until Sunrise if you set the sunset-to-sunrise schedule in step 3. That is the one you want when you are working late once, rather than every night.

From the menu bar

Faster route: open Control Center in the menu bar, click Display, and toggle Night Shift. This switches it on without opening System Settings at all.

On macOS Monterey and earlier

System Preferences → Displays → Night Shift tab. Same three controls, different wrapper.

One limitation worth knowing: Night Shift applies to displays whose colour macOS controls — the built-in screen and most monitors connected directly. Some external monitors manage their own colour and will not follow. If your MacBook screen goes warm and your external panel does not, that is why, and the fix is the monitor's own menu, not macOS.

Night Shift vs True Tone vs Dark Mode

These three get used interchangeably in blog posts and they do completely different things. This is what each one changes:

True Tone is the one people confuse with Night Shift most often. It uses the ambient light sensor to match the display's white balance to the light in the room, continuously, all day. Night Shift runs on a schedule and always goes warm. They stack: with both on, True Tone matches the room and Night Shift adds warmth on top after sunset.

Dark Mode does not touch the display's colour output at all. It changes what the software draws. A dark window emits less light than a white one, so it feels like a display setting, but the panel is calibrated exactly the same.

What the research supports

For sleep: mechanism yes, effect unproven

Evening blue light suppressing melatonin is not in doubt. Whether Night Shift removes enough of it to change how you sleep is a different question, and the answer so far is unconvincing. A 2021 study in the journal Sleep Health compared phone use with Night Shift on, phone use with Night Shift off, and no phone before bed. It found no meaningful difference in sleep outcomes between the two Night Shift conditions.

The likely explanation is dose. Brightness matters more than colour. A warm screen at full brightness held 30 cm from your face still delivers far more light to your retina than a cool screen at 20% brightness across the room. If you care about sleep, turn the brightness down first and the colour second.

For eye strain: no evidence

Night Shift is a software version of blue-light filtering glasses, and that intervention has been tested properly. A 2023 Cochrane systematic review of blue-light filtering spectacle lenses concluded that they probably make little or no difference to eye strain from computer use compared with standard lenses.

Singh, S. et al. (2023). Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database of Systematic Reviews.

Blue light is not what makes your eyes ache after a workday. Sustained near focus, glare, and a collapsed blink rate are.

For dry eyes: none, and this is the important one

Dry eye from screen work is an evaporation problem. Your tear film breaks up between blinks, and you blink roughly a third as often at a screen as you do in conversation. Nothing about the display's colour temperature changes that. The tear film does not care what wavelength is hitting it.

This matters because Night Shift is easy, free and visible, which makes it feel like you have addressed the problem. If your symptoms are burning, grittiness, or vision that goes briefly blurry and clears when you blink, Night Shift will not move them at all. Those are tear film symptoms, and they need a different fix.

A settings recipe that is actually worth your time

• Brightness first. A white page on screen should look about as bright as a sheet of paper on your desk. If the screen glows in a lit room, it is too high.
• True Tone on, all day. Free, automatic, no downside. It reduces the mismatch between your screen and the room.
• Night Shift on a Custom schedule starting two to three hours before bed, at a moderate warmth. Treat it as sleep hygiene, not eye care.
• Lower the monitor so the top of the screen sits at or just below eye level. A downward gaze narrows the eyelid opening and slows tear evaporation. Costs nothing.
• Fix the blink rate. This is the only item on the list that addresses the mechanism behind most screen-related eye discomfort, and the only one you cannot do with a setting.

Night Shift is a good feature aimed at a real problem. It is just aimed at the evening, not at your eyes.