Reaction time is the gap between something happening and you responding to it. In a simple online test it is the time from the screen changing color to your click. You cannot change how fast nerves carry signals, but you can remove a lot of the delay around them. Here is what matters, and how to measure whether it works.
Your equipment: a monitor with a higher refresh rate, a wired mouse and a fast browser all shave off milliseconds. Wireless or Bluetooth devices, TVs and slow screens add delay that has nothing to do with you.
Alertness: tiredness is one of the biggest factors. Test yourself after a normal night of sleep and again when you are worn out and you will usually see a gap.
Attention: if you are doing something else, your average gets worse and your slowest tries get much slower.
Anticipation: clicking early because you guessed the timing is not reaction. A good test uses a random wait so you cannot guess.
Type of stimulus: people generally respond to sound and touch a little faster than to sight, and to simple signals faster than to ones needing a choice.
Age and practice: reaction speed changes across a lifetime, and people who practise a specific task get faster at that task.
Tips that actually help
Fix your setup first. Use a wired mouse, close other tabs, and a monitor with a high refresh rate if you have one. This is the quickest gain.
Sleep properly. Rest is the most reliable way to improve alertness and speed.
Warm up. Do a few practice tries before you count any results.
Relax your hand and keep your eyes on one spot. Rest your finger over the button and watch the center of the target instead of scanning around.
Practise in short sessions. A few minutes a day beats an hour once a week. Stop when your results get worse from fatigue.
Use the median, not your best. One lucky time tells you little. Compare averages over several tries and several days.
Train related skills. Fast-paced games, sports with a moving ball, and aim practice all train the link between seeing and acting. Try the aim trainer or the click speed test.
What is a good reaction time?
For a simple visual click test, results are often quoted at around 200-300 ms for most people, with lower being faster. Treat that as a loose guide only: your screen, mouse and browser each add some delay, so the number is most useful as your own baseline. Run the test, write down your average, and check again in a week.
For a simple visual test where you click as soon as the screen changes color, results are often quoted in the range of roughly 200 to 300 milliseconds. Your screen, mouse and browser add delay of their own, so compare yourself with your own earlier scores rather than with other people.
Can you improve your reaction time?
Yes, within limits. Practice, sleep, a faster display and input device, and good focus all help. Your nerve-signal speed does not change much, but the delay added by hardware, anticipation and distraction can be reduced.
Does caffeine improve reaction time?
Some studies suggest moderate caffeine can make people more alert, which may help reaction speed when you are tired. Too much can make you jittery and less accurate. The effect varies between people.
How often should I practise?
Short, regular sessions work better than one long one. A few minutes a day is enough to see whether your average moves. Stop when you are tired, because tired attempts are slower and add noise.