Dead Pixel Test & Touch Screen Test

About the Dead Pixel Test & Touch Screen Test

Find dead pixels, stuck pixels and other screen faults before you buy, return or repair a monitor, laptop, TV, tablet or phone. The test fills the whole screen with one colour at a time — black, white, red, green, blue, cyan, magenta, yellow and two greys — then grey and colour ramps and a grid of lines one pixel wide. Click, tap or press an arrow key to move on.

The touch screen test finds spots that do not respond: draw with several fingers at once, or swipe over a grid until every cell is green — cells that stay grey never registered a touch. There is also a plain screen light. Nothing flashes: the screen changes only when you ask, and at most about three times a second.

Common uses

• Checking a new monitor, laptop or TV within the return period.
• Inspecting a second-hand phone, tablet or laptop before paying for it.
• Showing a fault to a repair shop or for a warranty claim (take a close-up photo on the screen where it shows best).
• Finding where a cracked or worn touch screen no longer responds.

Dead, stuck or bright: what you may see

Each pixel has a red, a green and a blue sub-pixel.

• Dead pixel: no sub-pixel lights up, so the dot is black on every screen; it is easiest to see on white.
• Partly dead pixel: one sub-pixel is off, so the dot has the wrong colour on white (cyan when red is missing, for example) and is dark on that sub-pixel’s own colour.
• Stuck sub-pixel: one sub-pixel is always on, so it shows as a red, green or blue dot on black, and as a white dot on the screen of the other two colours (a stuck red is white on cyan).
• Bright pixel: all three stay on: a white dot on black.
• Dust or a scratch looks the same on every colour and often shifts when you look from another angle; a dot that stays exactly on one pixel is in the panel.

Backlight bleed, glow and uneven brightness

LCD screens are lit from behind. In a dark room the black screen shows light leaking in at the edges or corners: that is backlight bleed, and it stays in the same place when you move your head. IPS panels also show a glow in the corners that changes with the viewing angle and distance — move back and look straight on to tell the two apart. OLED screens have no backlight, so their black should be completely black.

The grey screens show uneven brightness: cloudy patches, darker edges or faint bands. A little unevenness is common, especially on large and curved screens; judge how much bothers you with ordinary content too.

Why there is no flashing “pixel fixer”

Some sites flash colours rapidly to “unstick” pixels. This page does not, and it limits how quickly the screen can change, because flashing more than three times a second can trigger seizures in people with photosensitive epilepsy (W3C WCAG: Three Flashes or Below Threshold). A dead pixel is a hardware fault that no picture can repair. A stuck pixel sometimes recovers on its own; if it does not, check the manufacturer’s pixel policy — most say how many faulty pixels, and where, qualify for a repair or replacement.

The touch screen test

The test reads every finger, pen or mouse pointer with the browser’s Pointer Events, and the page shows how many touch points the device itself reports. In Draw mode each finger draws in its own colour: a line that breaks where your finger did not lift, or a finger that does not draw at all, marks a spot that does not respond. In Grid mode swipe over every cell until the screen is green — the bar of buttons covers a strip of the screen, so move it to the other edge with ⇅ to reach the cells under it; the result counts the cells that never registered a touch and shows where they are.

Test with the case and screen protector you normally use — an air bubble, a crack or a protector that is lifting can make a spot unresponsive — and with dry hands.

Screen light

The screen light fills the display with white or a warmer tint and keeps the screen on while it is open, where the browser allows it. Below 100 % the colour is darker; the screen’s own brightness is not changed, so turn it up for the most light.

Limitations

• You judge the result by eye: the page cannot see your screen, so it cannot find faults by itself.
• Colour profiles, night light, HDR modes and “dynamic contrast” change what the screen shows; switch them off for a fair test.
• iPhones do not let web pages go full screen, so Safari’s bars stay visible; some TV and kiosk browsers cannot go full screen either.
• The 1-pixel grid lines up with the screen’s pixels only at 100 % page zoom and when the screen runs at its native resolution.
• The number of touches is what the browser reports; some devices limit it, and some browsers stop the page from seeing touches at the very edge of the screen, where system gestures start.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.