Online Stopwatch & Countdown Timer
This free online stopwatch and timer runs entirely in your browser, so there is nothing to download or install. Use the stopwatch to measure elapsed time with millisecond precision and record lap (split) times, or switch to the countdown timer to count down from any duration you set and get an audio alert when it reaches zero.
Because the tool relies on the browser's high-resolution performance clock, timing stays accurate even if the tab is running in the background. It is handy for workouts, cooking, study sessions, presentations, games and any task where you need to track or limit time without reaching for a physical clock.
How it works
The stopwatch counts up from zero as elapsed = now − start, displayed as HH:MM:SS.mmm; each lap stores the current elapsed time. The countdown timer counts down as remaining = target − elapsed and fires an alert when remaining ≤ 0. Timing uses the browser's performance clock for millisecond accuracy.
Use cases
- Timing interval workouts, runs or gym sets with lap splits
- Cooking and baking with a countdown alarm
- Keeping presentations, speeches or meetings on schedule
- Timing study or focus sessions like Pomodoro blocks
- Timing board games, quizzes and classroom activities
Frequently asked questions
Is this online stopwatch accurate?
Yes. The stopwatch uses the browser's high-resolution performance clock rather than a simple counter, so it measures elapsed time to the millisecond. Accuracy is not affected by the tab losing focus, because the elapsed time is recalculated from timestamps rather than counted tick by tick.
What are lap times on a stopwatch?
A lap (or split) records the total elapsed time at the moment you press the lap button, without stopping the clock. It is useful for comparing repeated efforts, such as running laps or workout rounds, since you can see each interval alongside the running total.
Does the countdown timer make a sound when it ends?
Yes. When the countdown reaches zero the timer plays an audio alert so you are notified even if you are looking at another window. Make sure your device volume is on and that the browser tab is allowed to play sound.
Does the timer keep running if I switch tabs?
The timing stays correct because elapsed and remaining time are calculated from real timestamps, so switching tabs does not lose time. Some browsers slow background timers, which can delay the on-screen refresh slightly, but the final measured time and the alert remain accurate.
Do I need to install anything to use it?
No. It is a web-based tool that runs entirely in your browser with no download, sign-up or plugin required. Everything works client-side, so it also functions offline once the page has loaded.