about

About steadyhandtest

steadyhandtest is a small experiment: a steady hand test you run in the browser, using the motion sensors already in your phone. You hold the phone still for ten seconds, it measures how much your hand moves, and it turns that into a steadiness score and a picture of where your hand wandered.

I built it solo, as a side project. Partly because the "steady hands" challenge kept turning up and I wanted to know whether a phone could actually measure the thing, and partly because the engineering was a good puzzle — pulling an honest signal out of a sensor that was never designed for it. Every version, and every dead end along the way, is written up on the how it works page.

A few things it sticks to:

• No accounts, and nothing to install — it's a web page.
• No third-party trackers or ad scripts in the test itself.
• It runs entirely on your device. Your hold never gets sent to a server, because there isn't one.
• It's free.

Under the hood it's plain HTML, CSS, and vanilla JavaScript — no frameworks, no build step. You can read the page source and see exactly what it does.

One thing it is not: a medical device. It measures motion, and that's the whole claim. If you're genuinely worried about tremor or a change in how your hands work, that's a conversation for a neurologist, not a web page.