Touch Screen Test
Touch with as many fingers as you like — each one is tracked live — then swipe across the whole pad to paint the grid. Cells that refuse to paint mark dead regions of the digitizer.
Touch and swipe anywhere in this box
Each finger shows a live circle. Swipe across every cell to paint the grid — any cell that refuses to paint is a dead zone. Works with mouse too.
Modern phones track 10 simultaneous touches; many Windows laptops handle 10, some budget panels only 5 — press all your fingers down at once and check the max counter. For dead zones, swipe methodically row by row rather than scribbling: a genuinely dead strip (a common digitizer fault after screen replacements) shows up as a clean unpaintable line. Erratic behavior — phantom touches, points jumping — is more often environmental: a damp screen, a cheap screen protector lifting at the edge, or a charger with poor grounding (unplug and retest; it's a famous culprit for ghost touches).