8 min read
Why Your Browser Score Is Slower Than a Laboratory One
The same task, measured two ways, produced a 65 ms gap in published work. That difference is larger than most effects people test for — here is where it comes from.
Measurement
How a number from a browser gets produced, and what it can and cannot tell you. Apparatus effects, timing precision, latency, and why browser scores are not laboratory scores.
A browser reaction test is a timing instrument, and like any instrument it has error bars that are rarely zero. This topic is about where those error bars come from — how long a pixel takes to change, how long a mouse takes to report a press, and what a JavaScript timer can and cannot resolve — and how much of that error you can measure and subtract.
The practical consequence runs through everything else on this site. A browser number is not a laboratory number, the gap between them is large enough to matter, and no amount of careful clicking closes it. What it does support is comparing you against yourself on one setup, which is the comparison every test on this site is built for.
Everything here traces to a specific documented limitation, with the size of the effect stated where it is known, so you can decide which parts of a score to trust.
4 articles
7 min read
How Input Latency Compensation Actually Works
A median of five real clicks, subtracted from every result. What that measures, what it cannot reach, and how to get a clean latency reading on your own setup.
6 min read
Why Anticipation Is the Only Cheat That Matters
A randomised 1–3 second delay is what separates a measurement from a guess. How the too-early detector works, and the corner case a pre-timed press can still get through.
6 min read
What Your Browser Cannot Measure
Six real limitations of browser-based timing, how large each one is, and why that does not undermine the one comparison that matters: you against yourself.
Other topics
Interpreting scores
3 articles
What a reaction time actually means once you have one — reference ranges, statistical expectations, and the difference between a change you caused and a change you drifted into.
Test design
4 articles
The scoring ladders, ladders, and rules behind the individual tests, written out so a score can be interpreted rather than merely reported.