About Reaction Time Tool

10 free tests of reaction speed, attention and memory. No account, no signup, no upload. Everything runs in your browser and your scores stay on your device.

Why this exists

Reaction tests are one of the most searched for things on the web and most of the results are either a single page bolted onto a company blog, a relic from the 1990s that still works by accident, or a quiz designed to sell you a mattress. The good ones are good, and there are not many of them.

So this is a site that does one family of things and tries to do it properly: fast to load, usable on a phone, keyboard as well as mouse, no interstitial before you can start, and real writing underneath each test rather than three sentences of filler.

How the tests are measured

Timing uses the browser's high resolution clock, which is the most accurate thing available to a web page. The interval measured is between the moment the browser paints the signal and the moment your click, tap or key press arrives.

That interval includes your equipment as well as you. A 60 Hz monitor can only show the change at 60 discrete moments per second, which adds up to 16 milliseconds before your eyes are involved. Wireless peripherals add a little more, and a busy browser adds a little more again. Somewhere between 10 and 40 ms of any score is hardware. We say so on the pages rather than quietly presenting the number as pure biology, and it is the reason comparing against your own previous scores is worth far more than comparing against a stranger.

Where the reference numbers come from

The percentiles and the band tables are built from published population figures for simple reaction time, not from a database of this site's visitors. We could have described them as our own data and nobody would have checked. We would rather be able to point at what a number means.

That also sets the limit of what those comparisons are worth. A reference distribution tells you roughly where a score sits among people in general. It cannot account for your screen, and it is not a measurement of the population of people who use this site.

No leaderboard, and why

A public leaderboard on a test this easy to fake would rank persistence and browser consoles, not reflexes. Anyone can retry two hundred times and post the luckiest guess, and a page has no way to tell a genuine 140 ms reaction from an anticipation that happened to land. So there is no leaderboard here. Your personal best is saved on your own device, which is the only comparison that holds still enough to mean something.

Privacy, briefly

Nothing you do here is uploaded. There is no account and no results database. The only things kept are a handful of values in your own browser's local storage, all of them listed in the privacy policy, and clearing your browser data removes them permanently.

One thing these tests are not

They are not a medical assessment. They are not validated for diagnosis, and a browser is the wrong instrument for a question with a real consequence attached. If you are worried about your reaction time, memory or concentration, that is a conversation for a healthcare professional rather than for a web page. The terms set this out in full.

Contact

Corrections, bug reports and suggestions for tests are all welcome at hello@reactiontimetool.com, or through the contact page. If something here is wrong, tell us and it gets fixed.