How to test a touch screen
Press a finger on the grid and drag slowly, covering the box like you are colouring it in. Each square fills the first time it registers a touch. Work along the edges and into all four corners, because that is where digitisers fail first and where a drop most often breaks the connection.
Go slowly. Dragging fast leaves gaps between the points your browser reports, which looks like a dead zone but isn't. A real dead zone stays empty even when you press directly on it and hold.
How do I check multi-touch?
Place several fingers on the grid at once. A numbered circle appears under each one and the counter shows how many the screen is tracking, with the maximum kept as your record. Most modern phones handle ten simultaneous touches; many budget phones and older tablets stop at five, and some cheap panels stop at two.
If the count stops climbing well below five, or fingers already down jump position when you add another, the digitiser is either low-specification or faulty. Games and on-screen keyboards suffer most from this.
What causes dead touch zones?
A touch screen has a transparent grid of capacitive sensors bonded to the display. Dead zones appear when part of that grid loses contact with its controller, and the usual reasons are physical.
| Symptom | Likely cause | Fixable? |
|---|---|---|
| A stripe of dead squares across the screen | Damaged digitiser trace, usually after a drop | No — needs a screen assembly replacement |
| Dead patch near one edge or corner | Loose flex cable or bond failure from a fall or pressure | Sometimes, by a repair shop reseating the cable |
| Touch works everywhere but is erratic | Cheap or thick screen protector, or moisture on the glass | Yes — remove the protector, dry the screen |
| Phantom touches with no finger down | Failing digitiser or a bad third-party charger injecting noise | Try another charger first; often that's all it is |
| Edges unresponsive only in some apps | Palm-rejection or gesture zones, not a fault | Nothing to fix — expected behaviour |
Try this before assuming the screen is broken
- Take the case and screen protector off and test again — a protector with a trapped air bubble is a genuinely common cause.
- Dry your fingers and the glass; capacitive screens misread moisture.
- Unplug the charger. A poor-quality charger can inject enough electrical noise to cause ghost touches.
- Restart the device. A hung touch driver produces a dead area that a reboot clears completely.
- Test in this browser and in one other app, to rule out a single misbehaving app.
Buying a second-hand phone? Test this first
Touch damage is the fault most often hidden in a used-phone sale, because it is invisible until you use the exact area that is dead — and a seller demonstrating the phone will naturally avoid it. Spend a minute covering all 192 zones before you pay. Then check the display itself with the dead pixel test and confirm the panel speed with the refresh rate test.
If the screen fails, factor a replacement into your offer — on mid-range phones a screen assembly is often a third of the handset's used value, which usually makes buying a different unit the better call. Our best budget phones and best phones under ₹15,000 guides give you a new-price baseline to negotiate against, and foldables need extra attention along the crease, where touch response degrades first.
Frequently asked questions
Does this test work on a laptop?
Yes, on any laptop with a touch screen — and the grid also responds to a mouse or trackpad, so you can use it to check that a pointer tracks smoothly across the whole display. For a non-touch laptop, the mouse test is the relevant one.
Why do the edges of my phone screen not respond?
Modern phones deliberately ignore parts of the extreme edge to stop your palm triggering taps while you hold the device, and curved-edge displays reserve more. That is palm rejection, not a fault. Judge a dead zone by whether the middle portion of a region responds.
How many fingers should my screen detect?
Ten is standard on current phones and tablets. Five is common on budget devices and older models, and is perfectly usable. Two suggests a very low-cost panel. Whatever the number, what matters is that already-placed fingers stay put when you add another.
Can a stylus be tested here too?
An active stylus reports as a pointer, so it will draw on the grid and reveal dead zones the same way. Pressure and tilt aren't shown, because browsers expose those inconsistently across devices.