Timer
Pick a time, press Start and get a signal when it runs out.
5:00
The timer keeps time in a background tab, but the signal may not play if your phone is locked.
How it works
The timer measures against the clock rather than counting ticks, so it keeps the right time even when the tab is in the background and the browser saves power. The time left also shows in the tab title.
A time of your own can be written as minutes (7 or 2.5), as minutes and seconds (4:30) or as hours, minutes and seconds (1:15:00). Units work too: 4 min 30 s, 4m30s or 1 hr 15 min.
The signal is made in the browser without a sound file. You only hear it if sound is on and the tab was allowed to play audio when you pressed, which some phones block in silent mode.
Twenty-five minutes is the length of a session in the Pomodoro Technique: work one session, rest for five minutes, and take a longer break after four.
How the tool counts
When you press Start, the timer starts measuring like the stopwatch, with the browser’s clock for measurements, performance.now(), and with the computer’s ordinary clock for time in sleep mode. Five times a second it takes the time measured from the time you chose. The time left is rounded up to whole seconds, both while the timer runs and while it is paused. A five-minute timer therefore shows 5:00 for the first second and 0:01 for the last, and then shows that time is up.
If the computer’s clock is set back while the timer runs, for instance by a time server, the time left is not affected, and time in sleep mode is counted, also on systems where performance.now() stands still while the computer sleeps. A clock set forward by more than two seconds is counted as time passed, though, because the web page cannot tell it apart from sleep. Before October 2026 the timer counted only against the computer’s clock and followed every change to it.
The signal is three short tones at 880 hertz, each about a quarter of a second long, with just over a third of a second between their starts. It is generated in the browser only when the time runs out.
Entering a time
A single number is read as minutes, and a full stop or a comma is a decimal point: 90 becomes an hour and a half and shows as 1:30:00, 2.5 becomes 2:30, and 4.30 is 4.3 minutes, which is 4:18. For four and a half minutes, write 4:30. With colons, two numbers are read as minutes and seconds and three as hours, minutes and seconds. The seconds must be below 60, so 0:90 is not accepted, and in the longer form the same limit applies to the minutes. There is no upper limit, but a time of zero is not accepted.
A time can also be written with units: h or hr for hours, min or m for minutes and s or sec for seconds, with or without a full stop after them and with or without spaces, as in 4 min 30 s, 4m30s or 1 hr 15 min. The units go in the order hours, minutes, seconds. A number without a unit at the end is read as the next smaller unit, so 4 min 30 is 4:30 and 1 h 15 is 1:15:00, and after a larger unit the number must be below 60. Only the last number may have decimals, so 2.5 min is 2:30.
When the tab is in the background
Browsers run timers less often in tabs you cannot see. Firefox on a computer waits at least a second, and Firefox for Android waits at least fifteen minutes and may unload the tab altogether. Chrome checks such timers once a second, and since version 88 only once a minute when the page has been hidden for more than five minutes, has been silent for at least 30 seconds and the timer has run at least five times in a row. This timer runs five times a second, so it meets that last condition.
The time left is right when you return, but the signal and the time in the tab title can arrive up to a minute late. Keep the tab visible when the signal needs to sound at the right moment.