What is a 20 minute timer?
A 20 minute timer is an online countdown that runs for exactly 20 minutes and alerts you when it reaches zero. This one is already set when the page opens: press Start or the space bar and it counts down from 20:00, keeps exact time if you switch tabs or lock your phone, and rings until you stop it.
What 20 minutes is good for
Twenty minutes is the classic power nap: long enough to rest, short enough to stay in light sleep, and it is the "20" in the 20-20-20 rule for screen eyestrain (every 20 minutes look at something 20 feet away for 20 seconds). It also covers a HIIT session with warm-up, a quick workout video, a baking check for cookies and muffins, and resting a roast before carving.
For the eye rule, press Restart on the finished screen each time; for repeating rounds of work and rest, the interval timer does the counting for you. Keep screen on is on by default on phones so the alarm is not lost to auto-lock during a nap.
Start it in one click
There is nothing to set: the time is loaded, the Start button has keyboard focus on a computer, and the alarm sound, volume and screen settings are remembered from your last visit. If you need a different length, type it into the hours, minutes and seconds boxes or pick another preset below the timer.
It keeps counting in a background tab
The end time is fixed the moment you press Start, so a slow or sleeping tab cannot make it late: whenever the page is drawn it recomputes the remaining time from the clock. The alarm is pre-scheduled on the browser's audio clock and backed by a system timer and a desktop notification, and if the device was asleep when the time came, the page rings as soon as you return and shows how long ago the 20 minutes ended. On iPhone keep the tab on screen, since Safari pauses hidden pages; Keep screen on, which is on by default on phones, prevents auto-lock while it runs.
Alarm, repeat and phone use
Choose Beep, Bell, Digital, Soft, Cuckoo, Chime, Pipe or None and set the volume; all but the cuckoo are generated in the browser and work offline, and the cuckoo is a short clip of about 65 KB fetched once and then kept by the browser. The alarm repeats until you press Stop alarm, Space or Esc, and gives up after 60 seconds. Android phones vibrate as well; iPhones on iOS 17 or later play it even with the silent switch on.
Need a slightly different time?
The 15 minute timer and the 30 minute timer sit on either side. For 25 minutes you can press +1 min five times, but the Pomodoro timer already runs 25-minute focus blocks and the breaks between them.
Other time tools
For measuring how long something takes, use the stopwatch, which counts up and records laps. For the days and hours until a date, use the countdown. For alternating focus and break periods, the Pomodoro timer runs the whole cycle, and the interval timer repeats work and rest rounds for training. They all share this timer's clock engine, sounds and settings.