What this stopwatch does

Count time upward from zero with Start, Pause, and Reset, and press Lap to record split times so you can compare intervals. Add a recurring interval chime — a preset, or any minutes-and-seconds value down to the second — to get an audible cue as time passes, which is ideal for interval training or timeboxing. Press Fullscreen for a big, glanceable standby display.

How it works

The stopwatch is timestamp-based: it records when you press Start and adds up the elapsed spans across pauses, shown down to hundredths of a second. Because the elapsed time is computed from real timestamps rather than by counting ticks, it doesn't drift and stays accurate even when the browser slows the page down in a background tab.

Alarm-point chimes are generated in your browser with the Web Audio API — short tones synthesized on the fly, not downloaded files. Pick the interval chime's tone and Test it. Browsers only allow audio after you interact with the page, so the first tone plays once you press Start or Test. The fullscreen standby view uses the Fullscreen API and, where supported, a screen wake lock so the display stays awake; press Esc or Exit to return.

Frequently asked questions

Is anything I do here uploaded or saved?

No. The stopwatch and its chime sounds run entirely in your browser. Nothing is uploaded, logged, or stored — the sounds are generated on your device, and reloading the page clears everything.

What are laps?

While the stopwatch runs, press Lap to record the current time as a split. Each lap shows both the total elapsed time and how long that individual segment took, which is handy for timing repeated intervals.

What is the interval chime on a stopwatch?

It's an audible cue that repeats as time adds up — set it to chime every 30 seconds, every minute, or any custom interval down to the second. Great for interval workouts or keeping a task to a time budget without watching the screen. For a one-time alert at a specific time, use the countdown timer instead.

Does it keep timing if I switch tabs or lock my phone?

Yes. Because the elapsed time is based on real clock timestamps, it's always correct when you return. Some browsers slow background tabs down, so the on-screen digits and any chimes may only catch up the moment the tab becomes active again.

Does the screen stay on in fullscreen standby?

On browsers that support the Screen Wake Lock API, yes — the stopwatch requests a wake lock so the display doesn't dim while shown fullscreen. Where the feature isn't available it still works; your device's normal screen-timeout settings apply.

How do I clear my laps and start over?

Press Reset. It clears the elapsed time and the lap list and returns the stopwatch to zero, ready for a fresh run.