What is a 1 hour timer?
A 1 hour timer is an online countdown that runs for exactly 1 hour 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 1:00:00, keeps exact time if you switch tabs or lock your phone, and rings until you stop it.
What 1 hour is good for
An hour is the length of a lecture, a proofing bread dough, a slow simmer, a parking meter, a child's screen-time allowance and the "one hour then break" rule many people use for deep work. The display shows 1:00:00 and counts down through 59:59, so you always see minutes and seconds.
Over an hour you will almost certainly leave the tab or lock the phone. The alarm is scheduled on the audio clock and as a system timer, and the page restores a running timer after a reload, so you can close the tab by mistake and come back. If the computer sleeps, it rings the moment it wakes and tells you how late it is.
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 hour 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?
For 45 minutes use the 45 minute timer, for 30 the 30 minute timer. Longer than an hour? Type the hours into the first box: the timer goes up to 99:59:59, and the countdown tool is better for anything measured in days.
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.