90/20 focus timer
1 hr 30 min focus, 20 min break, then a 30 min long break after 2 sessions. 3 hr 50 min total.
Space start/pause R reset Esc stop
Focus sessions completed: 0
Settings
1 hr 30 min focus, 20 min break, then a 30 min long break after 2 sessions. 3 hr 50 min total.
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What this one is for
A 90/20 focus timer is built on the ultradian idea: Nathaniel Kleitman, who also co-discovered REM sleep, described a basic rest-activity cycle of roughly 90 minutes running through the night, and the popular extension is that a similar cycle continues during the day. That extension is much less settled than the sleep work it borrows from, and the 90 minute figure is an approximation even where the cycle is well described. Do not treat it as a biological deadline.
What is fair to say is that ninety minutes is close to the outer limit of sustained concentration for most people, and that pushing past it tends to produce time spent rather than work done. If you notice quality dropping at sixty, the honest number for you is sixty.
Twenty minutes off after a block that long is not a luxury. The preset runs two 90 minute blocks and then a 30 minute break, which is about four hours of deliberate work and roughly the most that anyone reliably manages in a day.
02
Good for
- Deep work on one problem with no context switching
- Practice sessions for music or a language
- Drafting something substantial in one sitting
- Mock exams and timed papers of about this length
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How it runs
1 hr 30 min focus, 20 min break, then a 30 min long break after 2 sessions. 3 hr 50 min total. Press Start, or hit Space. The digits turn green while a work block runs and grey on rest.
Sound is on by default: a rising pair for work, a falling pair for rest, a tick for the last three seconds and a three-note finish. Mute with the speaker button. The screen stays on while the timer runs and the tab title shows the time left.
Change anything in Settings under the timer. The last setup you used on this page is remembered in your browser.
Questions people ask
- Is the 90 minute cycle real?
- Kleitman’s basic rest-activity cycle is well established in sleep research. The claim that the same roughly 90 minute rhythm governs daytime attention is a plausible extension with far weaker support, so use 90 as a convenient ceiling rather than a fact about your brain.
- Ninety minutes is too long for me. What should I use?
- Drop Focus to 60 or 45 in the settings and keep the generous break. The useful part of this format is the long block plus a real rest, not the specific number.
- Should I take breaks even if I am in flow?
- If the work is genuinely flowing, finishing the thought is usually better than stopping mid-sentence. The risk is the other case, where you feel busy and are not producing anything. The marker exists so you get to notice which one it is.
- Does it keep the screen on?
- It requests a screen wake lock while running, so a laptop or phone left on the page should not dim off. The tab title shows the remaining time if you are working in another window.