Stopwatch challenge: can you stop it on exactly 10.00?
A free stopwatch game. Try to stop the clock on exactly 10.00 seconds, play blind with the numbers hidden, hit a random target, or see how many times you can stop on 0.10 in 10 seconds. Space bar works too.
How good is good?
| Off by | Rating |
|---|---|
| under 0.005 s | Perfect: the display reads exactly 10.00 |
| under 0.02 s | Incredible |
| under 0.05 s | Excellent |
| under 0.15 s | Very good |
| under 0.5 s | Not bad |
Human reaction time to a visual signal is typically around a quarter of a second, but this game rewards anticipation more than reaction: good players start pressing just before the target. Blind mode is harder because it tests your internal sense of time, which tends to drift by several percent over 10 seconds.
Challenge a friend
After each round, press Share my score to send your result. For a classroom or party game, put the page on a big screen and take turns; the full stopwatch has laps if you want to time a real race. Think you're fast? Compare yourself with the world record times, or race one live.
Questions people ask
How do you play the stopwatch challenge?
Press Start (or the space bar) and try to stop the clock on exactly 10.00 seconds. Your score is how far off you were, to the thousandth of a second.
What is blind mode?
The numbers disappear after 3 seconds, so you have to count the rest in your head. It shows how good your internal clock is.
What is the 0.10 round?
You get 10 seconds. Each tap starts or stops a tiny stopwatch, and every stop that shows exactly 0.10 counts as a hit. It tests reaction speed and rhythm.
Is my score saved?
Your best score for each mode is saved in this browser only. Nothing is sent anywhere.
How accurate is it?
It uses your browser's high-resolution timer. The screen refreshes about every 16 ms (60 Hz), so what you see can lag the true time by a few thousandths of a second; your score is calculated from the exact press time.
Last updated October 22, 2026.