Start by knowing what can move
Simple reaction time is close to a floor set by biology. The light has to reach your eye. Your brain has to see it, decide it is the signal, and send a command back down to your finger. That round trip never gets below about 100 milliseconds in anyone. Typical adults land near 231 ms on lab equipment, according to Woods and colleagues (2015).
So the realistic question isn't "how do I make my nervous system faster", because you largely can't. It is "how much of my current score is avoidable loss", and the answer for most people is: quite a lot. State, technique and equipment together account for far more day-to-day variation than any training programme will.
What actually works
Sleep, by a wide margin. Reaction speed is one of the most reliable casualties of sleep loss, and the effect accumulates. In Van Dongen and colleagues (2003), people who slept only six hours a night for two weeks ended up thinking as poorly as people who had skipped sleep for two whole nights. And they rated themselves as only slightly off. That last part is the trap: chronic sleep restriction degrades your performance and your ability to notice it at the same time. If you want a faster number tomorrow, sleep is the highest-yield intervention available and it is free.
Time of day. Alertness follows a daily rhythm, and for most people it dips in the early afternoon and again in the small hours. Testing at your personal peak instead of your trough can move a score by more than a month of practice would. It also means that comparing a morning result with a late-night one tells you about your circadian rhythm, not your ability.
Warming up. Your first run of anything is nearly always your worst, because part of it is spent learning what the task wants. Two or three throwaway rounds before the run you actually count removes a chunk of that. This is not cheating; it is the difference between measuring your reaction and measuring your confusion.
Hardware, more than people expect. A standard screen costs you about 8 ms compared with a fast gaming screen. The image simply cannot change until it redraws. A 125 Hz mouse can sit on your click for up to 8 ms where a 1000 Hz mouse holds it for about 1. Wired beats Bluetooth. None of this makes you faster, but it stops the equipment from making you look slower. See our guide on measurement accuracy for the full chain.
Posture and readiness. Rest your finger lightly on the button instead of hovering above it. That takes the travel distance out of the measurement. Keep your eyes near where the signal will appear so it lands in central vision. Breathe out and stay loose; tension slows the motor phase down, it does not speed it up.
What does not work, or barely does
Most "brain training". Practising a reaction test makes you better at that reaction test. Whether that transfers to anything else is a separate question, and the evidence for far transfer is weak. We wrote about this in what the evidence says about brain training. If your goal is a better number on this page, practice will deliver it — mostly by teaching you the task, not by upgrading you.
Reaction-time supplements. The category is mostly marketing. Caffeine is the one exception with real evidence behind it, and even its effect is modest. It helps if you are short on sleep or in an afternoon slump. It does almost nothing if you are rested and drink coffee every day anyway. Tolerance builds, so the person who drinks coffee all day gets less from a pre-test cup than the person who does not.
Chasing a personal best. A single fast round is mostly luck. Woods and colleagues found within-person variability of about 40 ms, meaning your own trials scatter that much around your own average without anything changing. If you run twenty times and keep the best one, you are collecting the tail of a distribution and calling it progress. Compare medians across sessions instead.
Video games sit in between. Action gamers do tend to score better on fast visual tasks, but which causes which is not settled, and where studies show gains they are strongest on tasks that resemble the game and fade further away from it.
The thing that looks like improvement but is not
The fastest way to a low number is guessing: starting your click before the signal appears, timed on the rhythm of the earlier rounds. It produces impressive figures and measures nothing. A well-built test blocks this. It makes the wait random and throws out any click that lands early. That is what our reaction time test.
Watch for it in yourself. If your score jumps while your canceled rounds also pile up, you are not getting faster. You are gambling more often, and only the winning bets get scored. The honest version of the same instinct is useful, though: in real situations, most of what looks like superhuman reaction is prediction. An experienced driver or goalkeeper is not reacting faster, they are reacting earlier because they read the cue sooner.
A sensible routine
If you want a number that improves and means something, do this. Sleep properly. Test at the same time of day, when you are alert. Use the same device and the same mouse every time. Warm up with two rounds you throw away. Keep the tab in front. And record the middle score of a full set, not your single best click. Then look at the trend across a week or two, not session to session. Most people find that their honest baseline is better than the number that first alarmed them.