Touchscreen Test
Paint a grid over your phone or tablet screen to find dead zones, run a 10-second hands-off check for ghost touches, and see how many fingers it tracks.
Tap Full screen, then paint the grid with your fingers. Each square fills in once your screen reports a touch inside it, so the squares left empty are the spots that never answered. A short hands-off check after that catches phantom taps, and the finger meter shows how many fingers the screen tracks at once. A mouse is ignored on purpose. The square size, the dropout rule and what a browser can’t see are under How we measure.
Rule out the easy causes first
A dead spot or a ghost touch isn’t always the digitizer. Peel off a cracked or lifting screen protector and run the grid again. Dry the glass, since water on the screen can register as touches and block real ones. If phantom taps only appear while the phone charges, unplug it and repeat the hands-off check: noise from a charger can reach the touch sensor and fake a touch. Restart the phone to clear a stuck driver. Still failing in the same spot after all that? It’s the screen.
How to use
- Go full screen. Tap Full screen so the grid covers the whole display. On an iPhone, Safari keeps its toolbars on screen, so the strips under them stay untested.
- Paint every square. Drag a finger slowly across the grid. A square turns solid blue once your screen reports a touch inside it.
- Run the hands-off check. Tap Hands-off check, set the device down, and keep your hands away for the 10-second countdown. A touch that arrives in that window leaves a red dot on its square.
- Press all your fingers down. Put every finger on the glass at once. The finger meter starts with one segment per touch point your browser reports, and it should fill all the way. Each extra finger past that adds a segment, up to 10.
Why test this
An on-screen key needs two taps. A swipe stops halfway. Apps open on their own. Any of that could be the screen, or just one app, and this test takes the app out of the question. Random taps miss a dead strip from a drop or a bad repair. Paint the grid and that strip stays empty. Ghost touches, the phantom taps that fire with nobody on the glass, show up in the hands-off check. Then press all your fingers down to see if the panel tracks as many touches as it claims. Run it before you pay for a used phone, and again after a screen replacement to make sure the new digitizer reaches every edge. Filing a warranty claim? A screenshot of the marked squares shows the shop exactly where the fault sits.
What the results mean
Watch the verdict at the top. While you paint, it counts the squares left. Clean means every square registered, nothing touched the screen during the hands-off check, and the finger count reached what your browser reports. Dead zone means at least one square stayed empty: either your touch dropped out over it mid drag, or it was still empty when the hands-off check ended. Paint a red square again before you trust it, because a fast swipe can skip a square. Ghost touch means a touch arrived while your hands were off, and the red dot shows where. Fewer fingers is only a hint. The screen tracked fewer touches at once than the browser reports, and on a phone that often just means your hand ran out of room. The finger meter keeps the most fingers seen at once against the number your browser reports, and the numbered circles count the fingers on the glass right now.
FAQ
- How do I find a dead zone on my touchscreen?
- Go full screen and drag a finger slowly over every square. A square that stays empty after a second slow pass is a spot where your screen never reported a touch. If your touch drops out while you drag, the empty square where it happened turns red.
- How do I test for ghost touch?
- Tap Hands-off check, lay the phone flat, and keep your hands, the case edge and any cable off the glass until the countdown ends. Every touch that lands on the grid in those 10 seconds leaves a red dot. Run it once on the charger and once off it, since a ghost touch that only shows up while charging points to the charger.
- Why does the test say 'Fewer fingers'?
- Your screen tracked fewer touches at once than your browser says it supports. Your browser picks that number. Chrome on Android tops out at 5, and Safari on an iPhone always says 5. A small screen may simply not fit that many fingers, so treat it as a hint and try again with both hands before you suspect the panel.
- Is a red square proof that my screen is broken?
- No. It shows where this device reported no touch during this run. Paint the square again slowly. A peeling protector, wet glass or a fast swipe can leave a square empty, while a spot that stays empty pass after pass is worth a repair quote.
- Does a screen protector affect the result?
- A clean, well-fitted tempered glass shouldn't. A cracked or lifted protector can swallow touches or create dead spots. If you suspect yours, run the test once with it on and once with it off and compare.
- Why does the test ignore my mouse or trackpad?
- It only counts finger and stylus input. A mouse has a single pointer and can't paint the grid or test multitouch. Open the page on a phone, tablet or touch display instead.
- Is this touchscreen test private?
- Yes. It runs in your browser and installs nothing. Your touch positions never leave the device.
How we measure
The test splits the touch area into a grid of squares about 48 CSS pixels a side, roughly a fingertip. It divides the width and the height by 48 and rounds to whole squares, so each one stretches a little to fill the area. Every touch your browser reports carries a position, and the square under it turns blue. Fingers and pens count. A mouse or trackpad doesn't. If the browser packs several touch reports into one event, the test unpacks them and reads each one. Nothing fills in between two reports, so a square that a fast swipe jumps over stays empty.
The test also follows the first finger down and checks its drag when you lift. The normal step is the median step between two reports in that drag. A dropout is a step at least 6 times the normal step in both distance and time, so pausing in place or flicking fast doesn't count. A new touch that lands within 200 ms of the lift and carries on the drag is a dropout too. If your browser doesn't list the reports inside each event (Firefox on Android doesn't), each event counts as one report and a step has to reach 12 times the normal step. Drags shorter than 8 reports or 120 CSS pixels aren't checked. The worst dropout gets a mark at its middle, and that square turns red only if no touch ever filled it in.
Hands-off check stops the painting and counts down 10 seconds. Every new touch that lands on the grid in that time is a ghost touch and puts a red dot on its square. When the countdown ends with any square painted, every square still empty turns red too. Paint a red square and it turns blue.
You get one verdict, checked in this order: Ghost touch, Dead zone, Fewer fingers, Clean. Clean needs every square painted, a hands-off check with no touch, and a finger count that reaches the number your browser reports. That finger count is the most touches the test saw at once, and the meter shows up to 10 segments. Fewer fingers is a warning, not a fault.
What a browser cannot see
A browser only sees the touches the phone's system passes on. A dead line thinner than one square can hide, because touches on either side of it still fill in the square it crosses.
The supported count comes from the browser, not the panel. Chrome on Android reports at most 5, because Android only tells Chrome that a phone handles at least that many. Safari on an iPhone always reports 5. The test reads that number as a floor. Past it, the meter grows by one segment for each extra finger the browser passes on, up to 10, and the count shows a single number.
Outside full screen the test watches only the grid, so it misses a ghost touch anywhere else on the page. An iPhone never lets a web page fill the whole screen. Safari's toolbars stay, and nothing under them gets tested.
Lifting a finger to move your hand looks the same as a dropout, so a dropout only counts against a square no touch filled in. The square size, the 6 and 12 times bars and the 200 ms window are starting values we haven't tuned on damaged screens yet. Treat a red square as a spot to test again: it only shows what this device reported during this run.
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