Reaction time test

Each round starts with a waiting screen. After a random delay of 1.5 to 4 seconds, the signal arrives: in visual mode the box turns green, in sound mode you hear a beep. Your reaction time is the gap between the signal and your click, tap or key press (Space and Enter work too). In visual mode, timing starts when the green box is actually drawn on screen.

If you react before the signal, the round is marked Too soon, shown separately and repeated. Because the delay is random, you can't learn the rhythm and anticipate it. Choose 5 rounds for a quick check or 10 rounds for a steadier result.

At the end you see every round in a bar chart plus four numbers:

• Median: the middle value when your times are sorted. One distracted round barely moves it, so it is the headline number.
• Average: the plain mean, which a single slow round can drag up.
• Best: your fastest valid round.
• Standard deviation: how much your rounds varied. A low value means you were consistent.

Example: your five rounds are 231, 248, 219, 402 and 240 ms. The average is 268 ms because of the slow 402 ms round. Sorted, the times are 219, 231, 240, 248, 402, so the median is 240 ms, a fairer summary. The high standard deviation tells you that one round was an outlier.

As rough guidance, simple visual reaction times on a typical computer setup often fall somewhere around 200–300 ms. Several factors move your number:

• Your hardware: displays add a few to tens of milliseconds of lag, and wireless mice, touchscreens and TVs outside game mode add more.
• Alertness: tiredness, distraction and time of day slow you down.
• Practice: results usually improve a little over the first few series.
• Age: simple reaction time tends to get slower with age.

Because hardware lag is baked into the measurement, compare results only on the same device and in the same mode.

Many people react a little faster to a sound than to a visual signal, so it's worth trying both modes. But your equipment matters here too: audio output adds its own delay, and Bluetooth headphones and speakers can add a noticeable lag on top of your reaction. For a fair sound test, use wired headphones or the device's built-in speakers.

In visual mode, a faster display shows the green box sooner. A 60 Hz screen draws a new image every 16.7 ms, a 144 Hz screen every 6.9 ms. Check yours with the refresh rate test.

• Sit comfortably with your finger resting lightly on the button or key, ready to press.
• In visual mode, watch the center of the box, not the edges.
• Use a wired mouse and, on a computer, a monitor in game mode if it has one.
• Get enough sleep. Being well rested reliably beats any trick.
• Warm up with a couple of series before you record a result, and watch your standard deviation drop as you settle in.

For other challenges, try the aim trainer, the memory test or the CPS test.

Your results go into a local leaderboard and history, stored only in this browser. Nothing is uploaded, and clearing your browser data deletes them. The share card turns your result into an image you can download or send from your phone's share menu.

This is an entertaining self-test of simple reaction time. It is not a medical or driving-fitness assessment, and the numbers depend on your device. If you notice a sudden change in your reflexes, coordination, hearing or vision, talk to a doctor.