Touchscreen dead zones and ghost touches: how to test them

A touchscreen has two common faults. A dead zone is an area that does not respond to your finger. A ghost touch is a touch the screen registers when nothing is touching it, or registers in the wrong place. The touchscreen test helps with both. Its grid mode shows which squares you have covered, and its draw mode shows each finger as a coloured trail. Run it in full screen, on the device itself, before you decide the screen is broken.

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Find dead zones with the grid

Open Grid mode and use the full screen button so the grid fills the display. Squares light up when a touch lands on them. Your aim is to cover every square. The counter reads "x of y squares covered" and climbs as you go.

Work methodically. Drag a finger slowly across each row, then down each column, and pay particular attention to the edges and corners, which are the places most often missed. A square that never lights up after careful touching is a candidate dead zone. Try it three or four times, because a fast swipe can skip a square without any fault in the screen. If you can, repeat with a different finger to see whether the same squares stay dark.

Then press Reset and go over the screen again, this time in a different direction. A true dead zone leaves the same squares unlit every time. Misses that move around the screen usually point to the speed of your gesture rather than a faulty panel.

Count the fingers

Draw mode shows a coloured trail for each finger, along with the number of touches now and the most at once. Use it to check multi-touch. Put down two fingers, then three, then more if you can, and check that each one leaves its own trail. If the count stays at one or two when you use more fingers, that can mean a fault, or a device or driver that limits how many touches it reports. Compare with the specification for your model before you conclude anything.

Where the device reports them, pressure and contact size also appear in this view. Many devices report neither, and a blank reading is not a fault.

Edge touches are not always the screen

Some dead areas at the very edge come from the operating system, not the panel. Phones and tablets reserve the edges for system gestures, such as swiping back from the side, and the system can take those touches before the page sees them. This test runs inside the browser, so it sees only the touches the browser receives. Check the edge gap in full screen, then look for a gesture or edge setting that would explain it.

Ghost touches

A ghost touch is a touch the screen registers without a finger on it. The usual signs are a menu opening, text appearing or the cursor jumping by itself. Common causes are:

• Screen protectors. A cheap protector that is not fitted flat can trap air or dust between the layers, and that changes how the panel reads touch. A protector that is too thick or not made for the device can cause similar problems. Remove it and test again.
• Moisture. Water or sweat on the glass, or trapped under a protector, can register as touch. Dry the screen and the edges, then retest.
• Chargers and grounding. A mains charger, especially a cheap one without proper earthing, can add electrical noise to a phone, tablet or laptop while it is plugged in. A ghost touch that appears only while charging, or stops when the cable comes out, points there. Try another charger, or use the device on battery to check.
• Cases. Some cases and grips can interfere with the sensor. Remove the case and retest.

Use the same method for each cause: change one thing, then test again. Removing the protector and unplugging the charger usually give the clearest answers.

Cleaning the screen

Switch the device off before you clean it, so stray touches cannot register while you wipe. Use a soft microfibre cloth, slightly damp, and wipe rather than spray. Liquid sprayed straight onto a screen can seep into the edges and cause the very ghost touches you are trying to fix. Avoid paper towels and harsh cleaners, which can damage the coating. Dry the edges and the gap under any protector, then test again.

When it is hardware

Software and environmental causes are the usual suspects, so work through them first:

1. Restart the device and install any pending system update.
2. Remove the screen protector and any case.
3. Unplug the charger and test on battery.
4. Dry the screen, then run the grid test again.

If a dead zone or ghost touch remains after those steps, and the same area fails every time after a restart, the fault is probably in the panel or its connection. A crack, a bulge in the glass or moisture under the surface are clear signs of damage. Check the warranty first. Repairs to a touch panel are often a whole screen replacement, so compare a repair quote with the warranty terms before you pay for anything.

Quick answers

Does a dead zone always mean a broken screen? No. Check the protector, the edges and any gesture settings first. A dead zone that survives a restart and a clean screen is more likely hardware.

How do I tell a ghost touch from a dead zone? A dead zone is silence where you touch. A ghost touch is activity where you do not. Unplug the charger and remove the protector, and if the phantom touches stop, the cause is one of those.

Can this test check the display itself? No. For stuck or dead pixels on the screen, use the dead pixel test. That is a separate fault from a touch problem.