Device check / 09
Reaction Time Test
Measure how fast you react: wait for the box to turn green, click, and get your average over five rounds in milliseconds, with early clicks and guesses ruled out.
Reaction Time Test: After a random wait of 1.5 to 4.5 seconds the box turns green. The test times the gap between the frame that shows the green and your press, with the browser's high-resolution clock. A press before the green is too soon, and one under 100 ms counts as a guess; neither is scored, and the round is run again. Runs 100% locally in your browser with zero server file uploads.
- Category
- Everyday tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
What the number includes
The time runs from the animation frame in which the box turns green to the moment your press reaches the browser. That includes your own reaction, but also the time the screen takes to show the frame and the mouse, trackpad, or touchscreen takes to report the press. Together these often add a few tens of milliseconds, which is why results on a computer are slower than the roughly 190 ms found for a light in laboratory studies.
A display with a higher refresh rate shows the green sooner, and a wired mouse usually reports sooner than a touchscreen. The monitor test shows what your display is doing; for a fair comparison over time, always use the same setup.
Why the wait is random, and what counts as a guess
The wait before green varies between 1.5 and 4.5 seconds, so you cannot press on a rhythm. Pressing during the red wait is marked too soon, and a press within 100 ms of the green is marked a guess: no one can see a change and move a finger that fast, so the press must have started before the green appeared. Neither is scored, and the round is run again.
Five rounds give a steadier figure than one. The median is the middle of the five times, unaffected by a single slow round; the average uses all five. Your best average is kept in this browser, next to the click speed test and typing test results.
How to use it
- Click the box or press Space to start.
- Wait for the red to turn green, then click or press Space as fast as you can.
- After five rounds, read your average, median, and fastest time.
Privacy & limitations
Everything runs in your browser. Nothing is sent anywhere, and your best average is kept in this browser only.
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Frequently asked questions
What is a normal reaction time?
In laboratory studies, young adults react to a light in about 190 ms on average, a figure accepted for over a century. Tests on a computer read slower because they include the delay of the mouse, the computer, and the display: classroom measurements at Clemson University typically come out around 268 ms.
Why do presses under 100 ms not count?
Signals take time to travel from the eye to the brain and on to the hand, so a press that quick was already on its way before the green appeared. Reaction-time research commonly discards such responses as anticipations, and so does this test.
Should I look at the average or the median?
The median ignores a single slow round, such as a moment of distraction, so it is the steadier figure. The average shows how consistent you were across all five rounds.
How can I react faster?
Being rested and alert matters most: reaction time slows with tiredness, distraction, and alcohol. On the test, keep a finger resting on the button and watch the middle of the box. Use the same device each time, since a different mouse or screen changes the result.
Free tool · runs in your browser · no account required