An eye break reminder
that actually fires

The 20-20-20 rule, briefly

The rule is simple on purpose: every 20 minutes, look at something about 20 feet away for 20 seconds. An optometrist popularized it in the 1990s as an easy-to-remember habit for people who spend their day in front of a screen. The numbers were chosen to be memorable, not because a study proved 20 is the optimal figure over, say, 15 or 30.

That distinction matters, so we wrote up the actual research separately: what the evidence says about the 20-20-20 rule, including studies that find real short-term benefit and studies that find no effect of the specific interval at all. The short version: taking breaks from near work is a reasonable habit. Whether it must be exactly 20 minutes, 20 feet, and 20 seconds is a much shakier claim than the mnemonic implies.

How Nox reminds you

Nox turns the habit into something that runs on its own, with a toggle in the menu bar panel:

• Pick your interval. 10, 15, 20, 30, 45, or 60 minutes, whatever fits your work.
• A real macOS notification, with sound. When the interval is up, you get a system notification: "Time for a 20-second break" and "Look at something 20 feet away to relax your eyes." It is not a browser tab or a menu bar blink you can miss.
• A live countdown in the panel. Open the menu bar panel any time and see exactly how long until the next reminder.
• A 20-second guided banner. When a break starts, a banner counts the 20 seconds down, so the break has a clear start and end instead of a vague "look away for a bit."
• A fix if notifications are off. If you declined notification permission, Nox shows you exactly where to turn it back on in System Settings, instead of silently doing nothing.

Break reminders run independently of Nox's filters. Turn on a spectral preset, dimming, or grayscale, and the reminder keeps its own schedule underneath, unaffected by whatever else the display is doing.

Honest limits

A break reminder is a nudge, not a treatment. It cannot fix dry eyes on its own, correct an uncorrected prescription, or resolve the ergonomic issues that cause a lot of screen-related discomfort in the first place: poor lighting, a monitor at the wrong distance, or hours without blinking enough. What it reliably does is interrupt a stretch of uninterrupted near work with a moment to look elsewhere, which is the one part of the 20-20-20 rule that the research agrees is worth doing. The rest, including the exact timing, is a starting point to adjust, not a prescription.

A reminder you have to build yourself, or one that is already there

What Nox changes on your Mac

Nox is a menu bar app for macOS 14 and later, downloaded as a signed DMG from this site. Break reminders are a local timer and a system notification; they read no data and send nothing anywhere. Toggling reminders off stops them immediately. To uninstall, quit Nox and move it from Applications to the Trash. Details on data handling are in the privacy policy; support is support@getnoxapp.com.

Frequently asked questions

What is the 20-20-20 rule?

It is a memory aid for taking screen breaks: every 20 minutes, look at something roughly 20 feet away for 20 seconds. An optometrist coined it in the 1990s as an easy-to-remember habit, not as a number tuned by a clinical trial.

Does the 20-20-20 rule actually work?

The evidence is mixed. Some research finds reminders reduce eye strain and dry eye symptoms while people are using them. Other research found no difference in symptoms, reading speed, or accuracy across break intervals of 5, 10, 20, or 40 minutes, and found blink rate drops during screen use regardless of how far away you look. Breaks still make sense as a habit; the exact numbers are a guideline, not a proven formula. See the full breakdown of the research.

What happens when Nox's break reminder fires?

You get a real macOS notification with sound: "Time for a 20-second break" and "Look at something 20 feet away to relax your eyes." The menu bar panel also shows a live countdown to the next break and a 20-second guided banner you can use as a visual timer.

Can I change how often the reminder fires?

Yes. Pick an interval of 10, 15, 20, 30, 45, or 60 minutes in the menu bar panel. The 20-minute default matches the 20-20-20 rule, but nothing about that number is mandatory.

What if I declined notifications for Nox?

Nox detects that notifications are off and shows exactly how to re-enable them in System Settings. Without notification permission the reminder cannot alert you, though the in-panel countdown still runs.

Does Nox change my Mac permanently?

No. Break reminders are a timer and a notification, nothing more. Turning the toggle off stops the reminders immediately, and uninstalling is quitting Nox and moving it from Applications to the Trash.