Everyone knows their step count; almost nobody knows how even their steps are. Walk for thirty seconds and get a number for it — timing consistency and left-right alternation, measured from your pocket.
Phone in a trouser pocket (best) or held still in one hand. Find 30 seconds of unobstructed walking — a hallway loop is fine. Walk like nobody's measuring, which is hard, we know.
Variability is the spread of your step intervals (coefficient of variation). Healthy adults walking normally typically land somewhere under ~4–5%; tired, distracted, or carrying-a-hot-coffee walks run higher. Alternation compares your alternating intervals (a proxy for left-vs-right timing): near 0% is symmetric; a persistently large number can just mean a phone bouncing oddly — or a real limp you already know about.
The honest part: this is a consumer curiosity built on a phone sensor, not a clinical gait lab, and one test is a snapshot, not a diagnosis. Where it gets genuinely useful is trends — the same pocket, the same loop, once a week. Researchers use gait variability as a marker worth watching; you can watch yours for free. If something hurts or a number jumps and stays jumped, that's a conversation for a professional, not a web page.