Timer

Pick a length, press start

Every duration here has its own page and its own address, so a fifteen-minute timer is a link you can bookmark, pin to a tab or send to somebody. Press start and the countdown runs; press space and it pauses. When it reaches zero the page flashes and, unless you turned sound off, an alarm plays.

Why it stays accurate in a background tab

Browsers throttle background tabs heavily — a script that counts its own ticks can fall a minute behind while you read something else. This one never counts ticks. It records the moment the countdown should finish and, on every frame, subtracts the current time from it. Switch tabs, lock the phone, come back an hour later: the number you see is the right one, because it was worked out from the clock rather than accumulated.

The remaining time also rides in the browser tab title, so the countdown is readable without the page in front of you. On phones the screen is asked to stay awake while the timer runs.

Timer, stopwatch, countdown — three different things

A timer counts down from a length you choose and signals at the end; that is this page. A stopwatch counts up from zero until you stop it. A countdown to a moment — a date, a time of day — is a different question again, and it lives on our how long until pages. This timer stops at twenty-four hours for exactly that reason: anything longer is a countdown to a date.

If you wanted the arithmetic instead

Sometimes the question is not «count this down» but «how much is this». Five minutes is 300 seconds, and the seconds converter turns any number of seconds into minutes, hours and days. It answers a different question with the same numbers.

The timers people set most