Timer
00:00:00
Ready.
Lap times
How timing stays accurate
The stopwatch stores elapsed time accumulated before each pause plus the difference between the current monotonic timestamp and the latest start timestamp. Screen updates only render that value, so a delayed callback does not change the measured duration.
Worked example
If the stopwatch runs for 2.50 seconds, pauses for 5 seconds, then runs for 1.75 more seconds, the elapsed result is 4.25 seconds.
Limits and browser behavior
This online stopwatch supports dynamic hours beyond 99 and shows hundredths of a second, but it is not laboratory timing equipment. Closing or reloading this tab resets the stopwatch and laps.
Sound is generated locally after a user action. No remote audio file, notification permission, wake lock, microphone, or recording is used.
Privacy and accessibility
Timer values remain page-memory only and disappear when the tab is reloaded. Buttons are keyboard operable, state and phase changes are announced without announcing every tick, and reduced-motion preferences disable decorative motion without changing timing.