Touch screen test

Touchscreen faults come in very different shapes, so the test has four parts.

• Dead-spot finder: the screen is split into a grid and you “paint” it with your finger. Every cell that registers a touch turns green. Anything that stubbornly stays grey – or turns red at the end – is where the digitizer (the touch-sensing layer) isn't responding. Choose a coarse, medium or fine grid; small faults show up on the fine one.
• Multi-touch counter: shows how many fingers the screen detects at once, next to the number your browser reports (navigator.maxTouchPoints). Most phones handle 5–10 points; older or budget tablets sometimes only two.
• Drag continuity: a slow line should be continuous. If the line jumps or breaks in a band, that's a skipping zone. We also measure the event rate (Hz) the browser receives.
• Ghost touch log: watches without you touching and logs every touch that turns up on its own, with a timestamp and coordinates. If nobody touched the screen and touches still arrive, those are phantom touches.

Dead-spot finder: a scattered red cell is almost always just missed – paint it again slowly. But if a connected strip (say, a horizontal band) or a patch keeps coming back red, that points to a digitizer fault. After a drop or a crack, it usually shows up around the damage.

Multi-touch: if you see fewer points than fingers on the glass, the screen has hit its own limit. If the browser reports the same number, that's simply the hardware, not a fault. If the browser reports more but the test sees fewer, your fingers may be too close together – spread them out.

Drag: a red segment marks a big jump between two samples; a red dot means the screen briefly lost your finger. If it always happens in the same place, sensing is weak there. The Hz value is the browser's event rate; the panel's own touch sampling rate (often advertised as 120–480 Hz) can be higher, because browsers may coalesce samples.

Ghost touch: even one logged touch is suspicious if you're sure nobody touched the screen. The timestamps and coordinates show whether the phantom touches cluster in one spot.

The most common causes, from simplest to most serious:

1. Dirt and moisture: greasy fingerprints, water drops or condensation can trigger false touches. Wipe the screen with a dry microfiber cloth.
2. Screen protector: a bubbled, badly applied or very thick glass protector weakens sensing, especially near the edges. Try without it.
3. Charger: an ungrounded or low-quality charger can inject electrical noise that causes phantom touches while charging. Run the ghost touch test with and without the charger – if touches only appear while charging, suspect the charger.
4. Software: if the problem started right after an update, restart the device and check for a newer update.
5. Hardware: a drop, pressure or water damage can harm the digitizer or its connector. If the fault survives all of the steps above, have it looked at by a repair shop.

• Go full screen: the edges, where most faults show up, can only be tested properly in full screen, because the browser's address bar and system gestures swallow edge touches in normal view.
• Go slowly: the dead-spot finder and drag test are most reliable with slow, even strokes. We handle coalesced events for fast swipes, but slow movements give the clearest picture.
• Repeat: a fault is real if it shows up again in the same place.
• Compare: if someone in the family has the same model, run the test on theirs too.
• Laptops and monitors: touchscreen laptops and all-in-ones can be tested as well. You can try the tests with a mouse, but only real touches give meaningful results.

The test uses the browser's standard Pointer Events API and everything runs on your device: touch coordinates never leave it and nothing is recorded. If you've agreed to analytics cookies, we only count whether a test was started and finished (not any touch data), to improve the page.

If your display has other issues, the dead pixel test finds stuck or dead pixels and the refresh rate test checks your screen's Hz. For other hardware, try the keyboard test or the mouse test.