Tools
Touchscreen test
Paint the whole screen with your finger. Any area that doesn't fill is a dead zone.
How the test works
Multi-touch
Every finger on the screen gets its own ring. We record the most touches seen at once.
Dead-zone painting
Drag across the grid until every cell is filled. Cells you can't fill point to a touch dead zone.
Edges
The edge test asks you to trace each border, where touch problems often start.
Questions
How many touch points should my phone support?
Most modern phones and tablets support at least five simultaneous touches; many support ten.
Why does part of my screen not respond?
A screen protector, moisture, a charger with electrical noise or digitiser damage can cause dead zones. Test without the protector and charger first.