The stopwatch and countdown timer offers two modes: a stopwatch that counts up from zero with lap marking, and a countdown that ticks down to zero and stops. Both modes display to the hundredth of a second and support full-screen display. Timing data is not saved across page reloads.
Setting the countdown time
After switching to countdown mode, click directly on the hours, minutes, or seconds field and type the number — no need to tap arrows repeatedly. To set 25 minutes, click the minutes field and enter 25. Once started, the fields lock. After pausing, they remain locked; press reset first to re-enter a different time. Starting with all fields at zero shows a "please set a valid countdown time" prompt.
Lap marks in stopwatch mode
Clicking the mark button while the stopwatch runs adds the current cumulative time to the lap list, ordered newest-first. Laps are not cleared by pausing — only the reset button wipes them, and there is no way to recover them after that.
Full-screen and keyboard shortcuts
Full-screen makes the time digits fill the entire display, useful when you need to read the timer from across a room. In full-screen, the spacebar toggles start/pause and Escape exits. The full-screen button may require a user gesture on some browsers and cannot be triggered automatically.
Background tab accuracy
On most desktop browsers the timer continues running in a background tab with drift under ±50 ms. Mobile devices are more aggressive about suspending JavaScript timers when the screen locks or when the app moves to the background, which causes the timer to fall behind. Keep the page visible for anything requiring precise timing. Switching between stopwatch and countdown modes resets all state.