Reaction Time Test
100% FreeNo sign-upWait for the panel to turn green, then click or press Space as fast as you can. This is your measured browser reaction time, not a medical measurement. Everything runs in your browser.
How fast are your reflexes? Wait for the panel to turn green, then click or tap as fast as you can. Zerdly runs a five-round benchmark and reports your median reaction time, your best and slowest attempts and how consistent you were — all privately in your browser.
What is reaction time?
Reaction time is the delay between a signal appearing and you responding to it. In this test the signal is the panel turning green; your reaction time is how many milliseconds pass before you click or tap. It reflects how quickly your eyes, brain and hand work together.
How the Zerdly reaction test works
After you start, the panel waits a random two-to-five seconds so you can’t anticipate the signal. The instant it turns green, a high-resolution timer starts; when you respond, the gap is recorded. The random wait is scheduled separately from the measurement, so the timing stays accurate.
Average vs median reaction time
One distracted round can wreck the average of a short test. The median — the middle value once your times are sorted — shrugs off those outliers, so Zerdly uses it as the headline number and shows the average alongside it.
Why results vary between devices
Reaction results are affected by display refresh rate, mouse or touchscreen latency, keyboard delay, browser scheduling and overall device speed. Two people with identical reflexes can post different numbers on different hardware, so treat this as your measured browser reaction time rather than an absolute score.
False starts
If you click before the panel turns green, that round is a false start: it doesn’t count, and a fresh random wait begins. Watching your false-start count is a good way to tell whether you’re truly reacting or just guessing the timing.
How to get a more consistent result
Rest your hand lightly, watch the panel rather than the mouse, and don’t tense up trying to pre-empt the signal. A relaxed, ready posture usually beats an anxious hair-trigger, which mostly produces false starts.
Simple, choice and audio reaction
Simple reaction measures a single response to one signal. Choice reaction shows one of four arrows and asks you to press the matching key — it adds a decision, so it’s slower and reports accuracy too. Audio reaction replaces the visual cue with a generated beep; because audio output adds latency, treat it as its own scale rather than comparing it directly with the visual tests.
The Daily reaction benchmark
The 🔥 Daily is a fixed five-round test that’s the same for everyone each day. Finish it to build a local streak and watch your median over the last seven days. Like everything here it stays on your device — there’s no global leaderboard to game.
Frequently asked questions
What is reaction time?
Reaction time is how long it takes you to respond to a stimulus — here, the moment a panel turns green. It is measured in milliseconds and reflects how quickly your eyes, brain and hand work together.
How does an online reaction test work?
After a random wait, the panel changes to a clear 'click now' state and the timer starts at that exact moment using a high-resolution clock. When you click or tap, the gap between the signal and your response is your reaction time.
What is a good reaction time?
Most people land somewhere around 200–300 milliseconds for a simple visual reaction test. Faster is better, but consistency matters too — a steady set of results is more meaningful than one lucky fast click.
Why is median used instead of the average?
A single hesitation or distraction can badly skew the average of a short test. The median (the middle value) ignores those one-off outliers, so it's a fairer headline number. Zerdly shows both.
Why do results vary between devices?
Your display refresh rate, mouse or touchscreen latency, keyboard, browser scheduling and device speed all add small delays. That's why this is your measured browser reaction time on this device, not an absolute measure of your reflexes.
Are my results saved?
Your personal best and recent sessions are stored locally on your own device, in your browser. Zerdly never receives your results — nothing is uploaded.
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