How to use the touch screen test
The test has three modes. Multitouch draws a numbered, coloured circle under every finger, with crosshairs running to the edges of the area and a label showing the point's coordinates. Put down one finger at a time and watch the touching now and max at once counters climb — that tells you how many simultaneous touches your panel really supports, which is not always what the manufacturer claims. Lift and replace fingers quickly to check that every touch is picked up and released cleanly; a marker that stays behind after you lift your finger, or one that appears when nothing is touching, is a ghost touch.
Dead zones covers the area in a grid. Every cell you drag across turns green, and the coverage percentage tells you how much of the screen has registered. Fast swipes are interpolated so cells between two samples still count. When you think you have covered everything, press Show gaps: untouched cells turn red so you can go back over them. Draw leaves permanent lines — draw slow straight lines with a ruler edge to spot wobble, breaks in the line or offsets near the bezel.
Press Full screen (or F) before you start so the test reaches the very edges, which is where most damage and digitiser faults show up. Clear (or C) resets everything. On a desktop without a touch screen the mouse acts as a finger, and holding Shift while dragging adds a mirrored second point so you can see the pinch and rotation readout work.
What the readings mean
| Reading | What it is | Typical values |
|---|---|---|
| Max at once | The most touch points the screen reported at the same moment. | Phones and tablets: 5–10. Touch laptops: 10. Cheap panels and some kiosks: 2. |
| Sample rate | How often the digitiser reports a moving finger, measured from coalesced pointer samples while you drag. | 60–120 Hz on most phones; 240 Hz or more on gaming phones and iPad Pro. |
| Event delay | Time between the browser time-stamping the input and this page handling it. | Under 10 ms is good. Large values point to a busy page or a slow device. |
| Pressure | Force reported for each point, from 0 to 1. | Most finger touches show n/a: the hardware does not report force. Pens usually do. |
| Contact | The width and height of the contact area in CSS pixels, drawn as a dashed ellipse. | Roughly 20–60 px for a fingertip, if reported. |
| Pinch · rotation | Change in distance and angle between the first two fingers since the second one landed. | ×1.00 and 0° at rest. |
The sample rate is the digitiser's report rate, which is separate from the display's refresh rate. You can measure the display side with the refresh rate test. Neither figure is the same as full touch-to-screen latency, which also includes the display pipeline and can only be measured with a high-speed camera.
Finding and diagnosing dead zones
A dead zone is a patch of the screen where touches aren't detected. It usually comes from a cracked or delaminated digitiser, pressure damage, liquid getting behind the glass, or a failing connector — in which case whole strips, often a straight band across the screen, stop responding. Use the fine grid and swipe slowly in overlapping rows; the edges and corners are the areas most often missed and most often faulty.
- A few scattered cells stay red: go over them again slowly. If they fill in, you simply missed them. If a cell never fills however you touch it, that spot is dead.
- A straight band won't register: a classic digitiser or ribbon-cable fault. It needs a screen replacement or reseating the connector.
- Touches register in the wrong place: in Draw mode your line appears offset from your finger. Try the device's calibration tool, if it has one, and remove any thick or lifted screen protector.
- Phantom touches: markers appear by themselves. Common causes are a charger with poor grounding, moisture on the glass or a bent frame pressing on the panel. Unplug the charger and dry the screen before assuming a hardware fault.
For a panel that looks wrong rather than responds wrongly, a dead pixel test checks the display itself.
Browser limits worth knowing
The test uses standard Pointer Events, so it works the same way in every modern browser on phones, tablets, touch laptops and all-in-ones. A few things are outside a web page's control. The operating system reserves some gestures — edge swipes for back or home, three-finger screenshots, four-finger app switching on iPad — and when it takes over a touch the browser cancels it; the test notes this rather than treating it as a fault. Palm rejection can also drop large contacts on purpose. iPhone and iPad report finger contact size to the browser but not finger pressure, and many Android panels report a constant pressure. Full-screen mode isn't available to web pages on iPhone, so turn the phone to landscape and scroll so the test area fills the screen instead. Nothing you draw or touch is recorded or sent anywhere.
Frequently asked questions
How many touch points should my screen support?
Most modern phones and tablets detect ten simultaneous touches, and five is the practical minimum for pinch, rotate and gaming controls. Touch-screen laptops and Windows tablets usually support ten. If the test shows only two points, the panel is either a basic two-point digitiser, common in cheap monitors and kiosks, or the driver is limiting it.
How do I check my phone for a dead spot on the screen?
Open the test, tap Full screen, choose Dead zones and the Fine grid, then swipe slowly across every row. Press Show gaps to highlight cells you missed and go over them again. A cell that never turns green however you touch it is a dead spot. Remove a thick or lifted screen protector before you start.
Why does pressure say n/a?
Most touch screens do not measure how hard a finger presses, so browsers report a fixed default value and the test shows n/a rather than a meaningless number. Styluses such as Apple Pencil, Surface Pen and S Pen do report pressure and usually tilt too, and those values appear in the table while the pen is on the screen.
What is touch sample rate and why does it matter?
It is how many times per second the screen reports the position of a moving finger. A higher rate makes drawing smoother and games feel more responsive. The test reads the individual samples that browsers group into each frame, so it can show 120 or 240 Hz even when the display refreshes at 60 Hz. Keep a finger moving steadily for a few seconds to get a stable reading.
Can I use this touch screen test without a touch screen?
Yes. The mouse acts as a single finger, so you can try every mode, and holding Shift while dragging adds a mirrored second point to demonstrate the pinch and rotation readout. The device panel tells you whether the browser can see a touch screen at all, which helps when a touch monitor isn't being detected.
Why do my touches disappear near the edge of the screen?
The operating system claims edge swipes for back, home and notification gestures, so it may cancel touches that start at the very edge. Test the edge by starting just inside it and dragging outwards. If a strip along one edge never responds even then, the digitiser or its connector is the likely cause.