Online Stopwatch
Counts up, takes laps, and reads from the back of the room. Space starts and stops it, L takes a lap, and it stays accurate even when the tab loses focus.
Why a browser stopwatch usually loses time
Start one in a tab, go and do something else, come back: it is behind. That is not one badly written site, it is how browsers save battery. Timers in tabs you are not looking at get slowed down or frozen outright, so anything counting its own seconds simply misses some, and the error accumulates the longer it runs.
This one does not count seconds. It records the exact clock time you pressed Start, and every update asks the system clock how long has passed since. A throttled background tab changes how often the number on screen refreshes. It cannot change what the number says.
Laps, and what a split actually is
Press Lap and it records the total on the clock at that instant. The table shows two numbers per row, and the difference between them catches people out. The total is time since you started. The split is time since the previous lap, which is almost always the one you care about: it is how long that leg, that rep, or that section actually took.
Splits are worked out from the recorded totals rather than measured separately, so they always add back up to the total exactly. The fastest split is highlighted, and Copy gives you the whole table as tab-separated text that pastes straight into a spreadsheet.
Built for the front of the room
- Big enough for the back row. Full screen fills the display with the clock and nothing else.
- Projector without the clutter. Send it to a second screen and the room sees a clean clock while your controls stay on your laptop.
- Hundredths, or not. On for timing a sprint, off when a flickering two digits at the end is just noise on a wall.
- Label it. A caption above the clock so the room knows what is being timed.
Where people use it
- PE and sports — heats and laps, where the split between laps is the whole point.
- Classrooms — timing an activity when you do not know in advance how long it should take.
- Talks and rehearsals — finding out how long a section actually runs before you decide what to cut.
- Anything you need a record of — the lap table copies out, so the numbers survive the session.
Questions
Does it keep accurate time if I switch tabs?
Yes, and that is the main reason this one exists. Browsers slow down or freeze timers in tabs you are not looking at, so a stopwatch that counts its own ticks quietly loses time. This one records the clock time you pressed Start and works out the elapsed time from the system clock on every update. Throttling a background tab changes how often the number repaints, never what it says.
What is the difference between a stopwatch and a timer?
A stopwatch counts up from zero, so you use it when you do not know how long something will take and you want to find out. A timer counts down from a number you set, so you use it when the length is decided in advance. If you need the second kind, the full-screen countdown timer is the one you want.
How do lap times work?
Press Lap while it is running and it records the total on the clock at that moment. The table shows each lap's split, which is the time since the previous lap, alongside the running total. The fastest split is highlighted. Copy sends the whole table to your clipboard as tab-separated text, which pastes straight into a spreadsheet.
Can I use the keyboard?
Space starts and stops it. L takes a lap. Both work anywhere on the page except while you are typing in the label box, which is the practical advantage a laptop stopwatch has over a phone.
Can I put it on a projector?
Yes. Full screen fills the display with the clock and nothing else. Second screen opens a separate window you can drag to a projector and full screen there, so the room sees a clean clock while the controls stay on your laptop. Both windows read the same system clock, so they stay in step.
Need the other direction? The full-screen countdown timer counts down from a length you set, on the same drift-proof clock.
What would make this tool better? A device that's missing, a detail that looks wrong, an option you went looking for and didn't find — all of it is useful. Send a note.
More in Classroom & Event Screens
See the collection- Random Name PickerSpin a wheel that won't repeat until everyone's had a turn
- Random Group GeneratorPaste a roster, get balanced groups in a click
- Full-Screen Countdown TimerA big, accurate countdown that won't drift in a background tab
- Raffle & Giveaway Winner PickerDraw one winner or several, with a proper reveal
- Yes or No WheelSpin the wheel, let it decide
- Random Partner GeneratorPair up a roster — with a plan for the odd one out
- Chore WheelSpin the wheel, take the chore it lands on
- Names in a HatPull a folded slip out of a hat, one name at a time
- Secret Santa GeneratorDraw names with the rules a real exchange needs, then print no-peek slips
Also coming to this collection: Full-Screen Countdown Clock, Full-Screen Stopwatch.