How to check a touch screen for dead zones
- Clean the screen and, if a dead zone shows up later, retest with the screen protector removed.
- Start the test. The page goes fullscreen and shows a grid.
- Swipe over every square, including the edges and corners. Touched squares turn green; the toolbar shows how much of the screen has responded.
- Look for gaps. A square or strip that stays dark after several swipes is a dead zone. Lines that break as you drag across one confirm it.
- Check multi-touch. Put several fingers down at once and read the touch count in the toolbar.
Tap the small ••• button in the top right corner to show the controls; use Reset to start over or Draw mode to trace freehand lines.
Common touch screen problems
Dead zones
Areas that never respond. Usually a damaged digitizer or a loose connector after a screen repair.
Ghost touches
Touches registering on their own. Often caused by a cracked screen, a lifting protector, moisture or a faulty charger.
Jumpy lines
Broken or zigzag lines when dragging slowly can mean a weak digitizer or interference from charging.
Missed multi-touch
Fewer touches detected than fingers down, which can affect pinch-zoom and games.
Checking the display itself too? Run the dead pixel test for dead or stuck pixels.
Frequently asked questions
How do I test my touch screen?
Start the test and slowly swipe your finger across the whole screen. Every grid square you touch turns green. Any square that stays dark after you have swiped over it several times is a dead zone where the screen is not registering touch.
How many fingers does my touch screen support?
Place several fingers on the screen at once. The toolbar shows how many touches are active right now and the most it has detected at the same time. Most phones and tablets support at least five simultaneous touches, often ten.
What are ghost touches?
Ghost or phantom touches are taps the screen registers when nobody is touching it. If squares light up or lines appear on their own during the test, the digitizer may be faulty, the screen protector may be lifting, or the charger may be causing interference.
What causes touch screen dead zones?
Common causes are a cracked or damaged digitizer, a bubble or misaligned screen protector, moisture, or a loose display connector after a repair. Try removing the screen protector and restarting the device before testing again.
Does the touch screen test work with a mouse or stylus?
Yes. Mouse and stylus input also fill in the grid, which is useful for checking a pen tablet or a touchscreen laptop's stylus. The multi-touch count only applies to fingers.