Touch Screen Test
Check a phone, tablet, or touch laptop for dead zones. Start the full-screen test and slide a finger across the grid — every square you touch lights up, and any that stays dark is a spot the screen never registered.
Open this page on the phone or tablet you want to test — the grid covers whatever screen it runs on.
Drag a finger in steady rows, like mowing a lawn — a continuous swipe leaves no gaps.
Retry dark squares slowly with a bare, dry finger. Still dark after a few passes means no touch is registering there.
Screenshot before you exit — the dark squares map exactly where the screen fails.
A touchscreen rarely fails all at once — it fails in patches. A drop, a hairline crack, a sloppy screen replacement, or moisture under the glass leaves a band or corner that ignores your finger while the rest of the screen works normally, so the fault goes unnoticed until a key or a button lands on the dead spot. The grid covers the whole screen, so a square that never lights up is a region your device never reported a touch for — a quick check before buying a used phone, after a screen repair, or when handing out devices in bulk. No app to install, and everything runs locally in your browser.
As you slide, the browser reports your finger’s position through Pointer Events, and every square your path crosses turns orange. Fast swipes are interpolated, so a quick flick still paints every square it covered, and several fingers can paint at once — though a single slow pass, row by row, tells you the most. A square that stays blue marks a region where the digitizer — the transparent touch sensor laminated over the display — never reported contact. On a laptop you can also paint with the mouse held down.
What if some squares never light up?
Rule out the easy causes first: clean the screen, dry your finger, and check the screen protector — a bubble, crack, or lifting edge blocks touch as thoroughly as a broken sensor. Then retry the dark squares with slow, firm strokes. If they stay dark, screenshot the grid before you exit: it shows a repair technician exactly where the digitizer has failed. The touch sensor and the display are separate layers — a screen can show a perfect picture yet miss touches (what this test finds), or register every touch over a defective picture, which is what the Dead Pixel Tester and the Display Test check.
Common causes of dead touch zones
| Cause | What happens | Fix |
|---|---|---|
| Cracked or delaminated digitizer | A drop can sever sensor traces even when the glass looks fine — touch dies in a band or corner | Screen/digitizer replacement |
| Screen protector faults | Bubbles, cracks, or a lifting edge insulate your finger from the sensor | Reseat or replace the protector |
| Moisture or grease | A film of water or oil conducts or blocks touch unpredictably — dead spots and ghost touches | Dry and clean the screen, then retest |
| Loose digitizer connector | The flex cable can unseat after a repair or a drop, so whole regions cut in and out | Have the connector reseated |
| Touch controller or firmware glitch | The controller mis-calibrates and ignores regions until it restarts | Restart the device; update the OS |
| Gloves or very cold, dry skin | Capacitive screens need a conductive touch, so the contact barely registers | Retest with a bare, warm finger |