Is an online stopwatch accurate in a background tab?

The reading is calculated from browser timestamps, so throttled animation frames do not lose elapsed ticks. The display updates when the page can draw again. Device sleep is different: some browsers pause their high-resolution clock during system sleep. After a reload, saved elapsed time is restored using the device wall clock, which can change if the clock is adjusted.

What are the keyboard shortcuts?

Space starts and stops, L records a lap, R resets to zero, and F switches full screen on and off (Escape also leaves full screen). The keys are listed under the buttons. They are ignored while you are typing in the countdown length box, so you can type 1h 20m without starting the clock.

How do the laps work?

Press Lap, or L, while the stopwatch is running and it records a split. The table shows each lap's own time and the total on the stopwatch when it was recorded, most recent first, with the fastest and slowest marked. Ties are marked too, and if every lap is the same length nothing is marked, because there is no fastest. Copy laps puts the table on your clipboard as tab separated text, which pastes into a spreadsheet as columns. Laps belong to the stopwatch; the countdown does not have them.

Does the countdown alarm work when the tab is hidden?

The page attempts three beeps when it observes the deadline and flashes the tab title. Hidden tabs, locked screens, muted audio and sleeping devices can delay or silence the sound. The overdue reading shows when the deadline was due on the browser clock; it does not prove a beep was heard. Closing the tab stops alarm delivery. A restored run has no automatic sound permission: Stop and Restart deliberately to try sound again.

What can I type in the countdown length box?

5:00 for five minutes, 90 for ninety seconds (a bare number is seconds), 1h 20m, or 00:00:30. Words work too: 45 sec, 25 minutes, 2 hours, 1.5h, 2m30s. A unit form can go over sixty, so 90s is a minute and a half. The seconds in a colon form cannot: 1:75 is refused, with the time you probably meant, 02:15, offered instead. Minutes can, as long as you are not also writing hours, so 90:00 is an hour and a half.

Does it keep running if I reload the page or close the tab?

A run you deliberately start is saved in this browser. On reload, its saved reading gains the positive time passed on your device wall clock. A closed page does no work and cannot sound an alarm. Clock adjustments can change restored elapsed time. Mode changes and timer actions save the current run; duration, precision and lap-sound edits save only those preferences. If storage is blocked, timing still works without remembering it.

Why does it show hundredths, and are they real?

Hundredths are a display resolution: the browser timestamp is truncated to centiseconds, so 59.99 does not round up to a minute. Browser clock precision, event delivery and your own reaction time affect a reading; this is no certified instrument. Choose Seconds if the extra digits are not useful.

Which timer should I use for repeated rounds, cube solves or dates?

Interval Timer runs repeated work and rest rounds, Pomodoro runs focus and break sessions, Classroom Timer sequences named activities with a progress bar, Chess Clock times two players, and Cube Practice Timer has scrambles and solve averages. Days Until counts to a chosen date at local midnight, including birthday or retirement dates and holidays. This Stopwatch has one digital timer; it does not offer animated races, voice activation or concurrent clocks.

Online Stopwatch

Measure elapsed time with Start, Stop, Resume and Reset. Record laps with individual and total times, fastest and slowest marks, and copy the table into a spreadsheet. Choose hundredths or seconds and a full screen view. The clock reads browser timestamps rather than adding ticks, so missed background updates do not accumulate drift. For a set duration, choose Countdown or open /stopwatch/countdown: quick lengths are 5, 10, 15, 20 and 30 minutes, with custom seconds, mm:ss, hh:mm:ss or units such as 1h 20m. Readings depend on the browser clock; a sleeping device may pause it.

Stopwatch · ready00:00.00press Start, or the space bar

Space start and stopL lapR resetF full screen

Mode

Show

Laps: 0

Sound at lap

The shortcuts work once you have clicked or tabbed into the tool, while the clock is on screen. Until then the space bar scrolls the page as usual.

Open Countdown Timer for a set duration. For repeated rounds use Interval Timer; for focus sessions use Pomodoro. Choose Classroom Timer for named activities and a progress bar, Chess Clock for two players, or Cube Practice Timer for scrambles and solve averages. For a birthday, retirement or holiday date, use Days Until (local midnight). For names or groups use Random Name Picker or Random Team Generator; use Dice Roller for random dice. This page has one digital timer; it has no animated races, themed clocks, voice activation or concurrent timers.

Common questions

Is an online stopwatch accurate in a background tab?: The reading is calculated from browser timestamps, so throttled animation frames do not lose elapsed ticks. The display updates when the page can draw again. Device sleep is different: some browsers pause their high-resolution clock during system sleep. After a reload, saved elapsed time is restored using the device wall clock, which can change if the clock is adjusted.
What are the keyboard shortcuts?: Space starts and stops, L records a lap, R resets to zero, and F switches full screen on and off (Escape also leaves full screen). The keys are listed under the buttons. They are ignored while you are typing in the countdown length box, so you can type 1h 20m without starting the clock.
How do the laps work?: Press Lap, or L, while the stopwatch is running and it records a split. The table shows each lap's own time and the total on the stopwatch when it was recorded, most recent first, with the fastest and slowest marked. Ties are marked too, and if every lap is the same length nothing is marked, because there is no fastest. Copy laps puts the table on your clipboard as tab separated text, which pastes into a spreadsheet as columns. Laps belong to the stopwatch; the countdown does not have them.
Does the countdown alarm work when the tab is hidden?: The page attempts three beeps when it observes the deadline and flashes the tab title. Hidden tabs, locked screens, muted audio and sleeping devices can delay or silence the sound. The overdue reading shows when the deadline was due on the browser clock; it does not prove a beep was heard. Closing the tab stops alarm delivery. A restored run has no automatic sound permission: Stop and Restart deliberately to try sound again.
What can I type in the countdown length box?: 5:00 for five minutes, 90 for ninety seconds (a bare number is seconds), 1h 20m, or 00:00:30. Words work too: 45 sec, 25 minutes, 2 hours, 1.5h, 2m30s. A unit form can go over sixty, so 90s is a minute and a half. The seconds in a colon form cannot: 1:75 is refused, with the time you probably meant, 02:15, offered instead. Minutes can, as long as you are not also writing hours, so 90:00 is an hour and a half.
Does it keep running if I reload the page or close the tab?: A run you deliberately start is saved in this browser. On reload, its saved reading gains the positive time passed on your device wall clock. A closed page does no work and cannot sound an alarm. Clock adjustments can change restored elapsed time. Mode changes and timer actions save the current run; duration, precision and lap-sound edits save only those preferences. If storage is blocked, timing still works without remembering it.
Why does it show hundredths, and are they real?: Hundredths are a display resolution: the browser timestamp is truncated to centiseconds, so 59.99 does not round up to a minute. Browser clock precision, event delivery and your own reaction time affect a reading; this is no certified instrument. Choose Seconds if the extra digits are not useful.
Which timer should I use for repeated rounds, cube solves or dates?: Interval Timer runs repeated work and rest rounds, Pomodoro runs focus and break sessions, Classroom Timer sequences named activities with a progress bar, Chess Clock times two players, and Cube Practice Timer has scrambles and solve averages. Days Until counts to a chosen date at local midnight, including birthday or retirement dates and holidays. This Stopwatch has one digital timer; it does not offer animated races, voice activation or concurrent clocks.

Time uses browser timestamps rather than counted ticks, so a background tab does not lose missed updates. Hundredths show display resolution, not certified accuracy. Device sleep may pause the browser clock; reloads use the device wall clock. A countdown reports how long ago its deadline passed; sound can be delayed or silent.