A stopwatch that counts up, with laps

Start it, take laps, read the splits. Elapsed time is measured against a monotonic clock, so the total is real time rather than however many ticks the browser allowed.

Laps and splits are different numbers

A lap is the time since the previous lap; a split is the total elapsed at that moment. Both are shown, because a set of laps without their splits cannot be added back up reliably once the list is long.

Accuracy you can actually rely on

The display refreshes on the browser’s animation frame while the underlying time comes from a monotonic source. That separation is why the reading stays correct across a throttled tab, and why the hundredths are worth showing at all.

Questions

Do the timers keep running if I switch tabs?

Yes. The countdown is measured against a monotonic clock rather than counted in ticks, so a backgrounded tab, a throttled timer or a laptop lid closing does not lose time — when you come back it shows what it should, not what it managed to count.

Is my data sent anywhere?

Timers, laps and clock choices are held in your own browser and are not sent to us. If you sign in and save something, it is stored against your account so it can appear on another device — that is the point of saving it.