▮ Device Bench

Device test · Display

Touch Screen Test

Sweep a finger across the grid and watch it paint. Every contact your screen registers fills a cell and drops a numbered marker, so dead zones stay visibly unpainted, ghost touches appear where you aren't touching, and multi-touch is tracked finger by finger. Everything runs in your browser — nothing is recorded or sent anywhere.

Active0 Max at once0 Pointer— Position— Coverage0% Viewport— Screen— Fullscreenoff

How this test works

The grid is the instrument. Every contact your screen's digitizer reports to the browser paints the cell under it and drops a numbered marker on the exact spot, so a working panel fills in solidly as you sweep a finger across it. What stays unpainted is the finding: a cell that will not paint no matter how deliberately you touch it marks a dead zone, and a straight band of them usually traces a failed row or column of digitizer electrodes. The readout keeps the numbers honest — how many contacts are on the glass right now, the most it has ever tracked at once, the last reported position, and what percentage of the grid you have covered. Full-screen mode rebuilds the grid over the entire display, because edges and corners are where touch failures usually start and the browser's own chrome normally covers them.

Under the glass sits a capacitive digitizer: a lattice of transparent electrodes whose field your finger disturbs. A controller chip scans that lattice, resolves each disturbance into a coordinate, and hands it to the operating system, which the browser surfaces as pointer events — pointerdown when a contact lands, a stream of pointermove events while it drags, pointerup when it lifts. Each simultaneous contact carries its own pointer ID, which is how this page tracks several fingers at once and labels each with its own marker. A mouse or a pen arrives through exactly the same pipeline with a different type label, which is why they paint here too — the readout names the pointer type so you always know which one you actually tested.

The limits are worth knowing. A dead zone and a dead pixel are different failures: this page tests the digitizer layer that senses touch, while the display underneath can show a perfect image over glass that senses nothing — if a region looks wrong as well as ignoring touch, run the dead pixel test to separate the two. A mouse passing this test says nothing about the capacitive layer, because it never goes near it. The maximum simultaneous touches you can register is capped by both the digitizer and the browser — many report no more than five or ten contacts, so a lower ceiling here is not by itself a fault. And this is a functional check, not a hardware diagnostic: it shows you where the screen fails, but it reads no sensor internals, cannot repair a failed digitizer, and a false dead zone from a damaged screen protector, moisture, or a glove will clear when the obstruction is removed.

Frequently asked questions

Part of my screen doesn't respond to touch. Is it broken?
First rule out the cheap causes: clean the glass, dry your hands, and take off any screen protector — a lifted or thick protector is the most common fake dead zone. Then restart the device, since a hung digitizer driver can ignore a region until reset. If a zone still will not paint after that, especially a straight-edged band, the digitizer in that area has likely failed, which on most phones means a screen assembly replacement rather than a repairable part.
How many fingers should my screen track at once?
Most phones and tablets track ten simultaneous contacts, and many laptop touch screens track five or ten. Press fingers down one at a time and watch the max-at-once readout climb; where it stops is the ceiling your digitizer, operating system, and browser agree on. A ceiling of five or ten is normal. What is not normal is a screen that drops an existing finger the moment another lands — that shows up here as a marker vanishing while you are still touching.
Can I test a touch screen with a mouse?
You can test the page with a mouse, not the screen. A mouse drag paints the grid through the same pointer events a finger sends, which proves the browser side works and lets you explore the tool on a desktop. But the mouse never touches the capacitive layer that actually fails, so a dead zone can only be found by a finger on the glass. The readout labels every contact mouse, pen, or touch, so there is no ambiguity about which you ran.
What is ghost touch, and will this test show it?
Ghost touch is the screen reporting contacts you never made — taps and swipes firing on their own. Rest the device on a table without touching it and watch this page: any marker or painted cell that appears by itself is a ghost touch, and the marker shows exactly where the digitizer thinks the contact is. Common causes are a cheap or failing charger injecting electrical noise (unplug it and retest), moisture at the screen edge, or physical digitizer damage. The test makes the ghosts visible; fixing them means removing the cause.
Why does the test offer a full-screen mode?
Because the browser's own interface covers the exact places touch screens fail first. Dead zones cluster along edges and in corners — where flex cables connect and where drops land — and in a normal tab those strips sit under the address bar and toolbars, where this page cannot see your touches. Full-screen mode rebuilds the grid over the entire display so every part of it is testable. Tap once to reveal the exit button, or press Esc on a keyboard; if the browser refuses full screen, the grid still covers the whole viewport.

Related tools

touch anywhere to test · ✕ or Esc to exit