Online Stopwatch
A free online stopwatch with lap timing, accurate to 1/100 of a second. Start, pause and record laps in one click — no download, no sign-up, ready the moment the page opens.
Laps you record will appear here.
About This Online Stopwatch
An online stopwatch measures elapsed time instead of counting down. Press Start and the stopwatch clock begins running; press Lap to snapshot a split without stopping; press Pause or Reset whenever you need. Because it lives in the browser, this online stopwatch is always where you are — open the page on any device and the stopwatch clock is ready.
The display shows MM:SS.cc — minutes, seconds and hundredths — and grows to H:MM:SS.cc once you pass the hour mark. Every lap you record shows both the split time and the total elapsed time, which makes this online stopwatch as useful for a single sprint as for a long experiment or workout.
Timing several participants? Run one online stopwatch for the whole field and press Lap as each person finishes — the split column becomes the results table, already in finishing order. For repeated attempts, reset between rounds and keep each measurement separate, so times from different rounds never mix.
How to Use the Online Stopwatch
- 1
Start the stopwatch clock
Press Start (or hit Space). The online stopwatch begins immediately and the digits update every hundredth of a second.
- 2
Record laps
Tap Lap — or press L — to save a split. The online stopwatch keeps running while your laps stack up in the table.
- 3
Pause and resume
Pause freezes the display without losing the total. Resume continues the same online stopwatch session from exactly where it stopped.
- 4
Reset when done
Reset clears the time and every lap. The online stopwatch is then ready for the next race, round or experiment.
Classroom Uses for an Online Stopwatch
A stopwatch clock earns its place in lessons where every tenth matters:
Science experiments
Time reactions, dissolving rates and pendulum swings. The online stopwatch gives hundredth-second precision that a wall clock cannot.
Sports day and PE
Run races with lap splits for each attempt. The online stopwatch table shows best and slowest laps at a glance.
Speaking and fluency practice
Time one-minute talks and repeated reads. Seeing the online stopwatch improve across attempts motivates students visibly.
Debate and presentations
Keep speeches inside the limit while the stopwatch clock records exactly how long each speaker actually took.
Everyday timing
How long does the homework really take? Time one attempt with the online stopwatch and plan the week with real numbers.
How Accurate Is the Stopwatch Clock?
This online stopwatch measures time with performance.now(), the browser’s high-resolution clock, and updates the display on every animation frame. It never adds up ticks that background throttling might delay — pause for an hour, resume, and the stopwatch clock still reports the true elapsed total. The result is an online stopwatch precise to 10 milliseconds of displayed time, which is far beyond what human reflexes can trigger.
Online Stopwatch Tips
- Use keyboard shortcuts — Space, L and R run the whole online stopwatch without reaching for the mouse.
- Record a lap at every transition to turn the stopwatch clock into a simple session log.
- Keep the page pinned: the tab title shows the running time, a mini stopwatch clock while you work elsewhere.
- Pair the online stopwatch with a countdown preset like the 1 minute timer for timed turns and quick rounds.
- Project the stopwatch clock during competition so spectators and competitors see the same running time.
- Reset between attempts rather than reusing laps — each online stopwatch round then stands alone.
Online Stopwatch FAQ
How accurate is this online stopwatch?
The stopwatch clock displays hundredths of a second and measures with the browser’s high-resolution timer, so the online stopwatch stays exact even through pauses and background tabs.
Can the online stopwatch record laps?
Yes. Press Lap while running and the online stopwatch stores each split with its total time, highlighting your fastest and slowest laps.
Does the stopwatch clock keep running in a background tab?
Yes. Elapsed time is computed from timestamps rather than ticks, so the stopwatch clock and the online stopwatch total remain correct after any switch.
Is the online stopwatch free?
Completely free, with no account and no limits. The online stopwatch works offline once the page has loaded.
What is the difference between a stopwatch and a timer?
A stopwatch clock counts up from zero to measure how long something takes; a timer counts down from a set duration. This site has both — the online stopwatch here and the countdown timers elsewhere.
Are my laps saved if I close the page?
No. Laps live only for the current session by design — refresh resets the stopwatch clock for the next measurement. Write down any splits you want to keep before leaving the page.
Can I time multiple people with one online stopwatch?
Yes. Start the stopwatch clock once and press Lap as each finisher crosses the line — the splits become the placings, in order.
Does the online stopwatch work on phones?
Yes. The buttons are sized for touch, and the online stopwatch runs in any modern mobile browser without an app. Bookmark it once and the stopwatch clock is one tap away on any device you carry.
Sources and technical references
The engine on this page updates the remaining time roughly five times per second (every 200 ms), the stopwatch resolves time to 10 milliseconds, and every duration accepts up to 24 hours. The specifications behind these claims are published openly:
- Web Audio API — MDN Web Docs
- Fullscreen API — MDN Web Docs
- performance.now() — MDN Web Docs
- High Resolution Time Level 3 — W3C
- HTML Standard: timers and user prompts — WHATWG
Last updated: 2026-09-28 · Maintained by the Classroom Timer team