How to run the multi-touch test
Tap Start multi-touch test. Scrolling and zooming are switched off over the test, so five fingers pressing at once can’t turn into a pinch that zooms the page. Put one finger down, then add more. Each finger gets the lowest free number, its own color and a trail that follows it.
The bar keeps two counts apart: how many fingers are down right now, and the most it saw at the same moment. Lifting and replacing fingers never adds to the second number, so it is a true peak, not a running total. Next to it is the device’s own claim, navigator.maxTouchPoints; MDN notes that phones on Android and iOS typically report 5, and computers without a touch screen report 0.
What to look for beyond the count
The peak is only half the test. With three or four fingers down, slide them slowly across the screen together, then spread and close them like a zoom gesture over different parts of the glass:
- Stable numbers: a finger that keeps its number for the whole slide is being tracked. A number that disappears and comes back as a new one means the touch was lost.
- Smooth trails: gaps or sudden jumps in one finger’s trail mark the spot where the screen lost it.
- Crossing paths: let two fingers pass close to each other. Some screens swap the two touches or merge them into one.
A count that stops at two whatever you do points to a screen that tracks two points only; the Android touch screen test page explains how Android describes these levels. To check every area of the glass, switch to Dead zones.
Source: MDN: Navigator.maxTouchPoints.