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Reaction Time TestBeta

Test your reaction time: click when the screen turns green. Five tries give your average, median, best and worst time — all measured in your browser.

The moment the screen turns green, click, tap or press Space/Enter as fast as you can. Clicking too early counts as a false start and is not recorded. You get 5 attempts in total.

How the test works

Click Start, then wait for the box to turn from grey to green. The wait before it turns green is random each time, between 1.5 and 5 seconds, so you can’t anticipate it by counting a rhythm. The instant it turns green, click, tap, or press Space or Enter as fast as you can. If you click before it turns green, that counts as a false start: it’s shown with a message but is not included in your result, and you simply get another try at that round. You get 5 valid attempts, then a summary with your average, median, best and worst time, plus a list of every attempt.

What changes your result

Several things affect a reaction-time measurement like this one, not just how alert you are:

  • Display refresh rate — most laptop and phone screens redraw around 60 times per second (60Hz); some redraw faster, at 90, 120 or 144Hz. Even after the page asks the browser to draw the green screen, the actual pixels only change on the display’s next refresh, adding up to one refresh interval of delay that no website can measure or remove (see the requestAnimationFrame documentation in Sources).
  • Input device — a mouse click, a touchscreen tap and a keyboard press each travel through a different path inside the operating system before the browser sees them, so they don’t always arrive with the same delay.
  • Browser and system load — other tabs, background processes, or a busy device can delay when your click reaches this page.
  • Practice and fatigue — reaction time tends to improve slightly over a few tries as you settle into the rhythm, and gets slower when you’re tired or distracted.

Because of this, treat the numbers here as a rough, browser-based estimate for comparing your own tries over time, not a clinically precise measurement.

Reading your summary

  • Average — the mean of your 5 valid attempts.
  • Median — the middle value when the 5 attempts are sorted; it’s less affected by one unusually slow or fast try than the average.
  • Best / worst — your fastest and slowest valid attempt.
  • Standard deviation — how spread out your attempts are; a small number means your attempts were consistent, a large one means they varied a lot.
  • False starts are listed separately and are not included in these numbers, since they measure how early you clicked, not how fast you reacted.

Privacy

The whole test, including the timer and the random delay, runs in your browser. No reaction time or click is sent anywhere. If your browser supports it, your single best time on this device is saved in this browser’s local storage so it can show up next time you visit — nothing else is stored, and you can clear it at any time by clearing this site’s data in your browser settings.

Sources

Frequently asked questions

Why doesn't a click before the screen turns green count?

Clicking early (a false start) means you reacted to something other than the color change — often to guessing when it would appear — so it wouldn't measure your reaction time. It's shown to you but excluded from your 5 valid attempts, and you simply try that round again.

Why do I get a different time every try?

Human reaction time naturally varies from moment to moment, and small technical factors add extra fluctuation: the display's refresh timing, how the input device reports your press, and other work your browser or device is doing at that instant. That's why the test takes 5 attempts and summarizes them instead of relying on a single click.

Is this as accurate as a laboratory reaction-time test?

No. Lab equipment can use dedicated hardware and displays with fixed, known refresh timing. A web page depends on the browser and screen it happens to run on, so results can shift for the same person between devices. Use it to compare your own attempts on the same device, not to compare exact numbers across different phones or computers.

Does tapping a touchscreen give a different result than clicking a mouse?

It can. Touchscreens, mice and keyboards each report input to the operating system through a different path, and some add a little more delay than others. Testing on the same device and input method each time makes your own comparisons more meaningful.