How to inspect a touchscreen for visual defects

A dark dot, pale patch, colored line or faint ghost image can make you wonder whether a touchscreen is damaged. Smudges, screen protectors and display settings can look like hardware problems, so inspect the panel under a few consistent conditions before deciding what to do.

The Display Test shows color patterns that can help you spot visible defects. This checks the picture, not whether the touchscreen registers taps. If taps are the problem, check them separately with the Touch Screen Test.

Inspect the touchscreen display

1. Open the Display Test on the device with the screen you want to inspect. If you are checking an external touchscreen, open the test on that display.
2. Clean the screen gently with a soft, dry microfiber cloth. Turn off the screen or wait for it to cool before cleaning, and do not press hard on the panel.
3. Use the test's color patterns to inspect the whole display. Look at white, black and solid colors such as red, green and blue. Check the center, edges and corners from a normal viewing position.
4. Look for dots, lines, patches, uneven brightness or an image that seems to remain faintly visible. Keep the brightness at a comfortable level, then repeat at a lower setting if the defect is hard to judge.
5. Rotate the device and view the screen straight on. If the display is connected to a computer, check that the same area looks abnormal outside the test too.

Do not push on a suspicious spot to see whether it changes. Pressure can make an LCD show temporary marks and may damage the panel. Take a photo of the screen if you need to show a repair shop, but remember that a camera can add patterns or color shifts that are not visible to your eyes.

What the result means

A tiny dot stays the same color on every test pattern

A dot that stays black, white or one color as the background changes may be a stuck or dead pixel. A stuck pixel can remain lit in one color, while a dead pixel usually stays dark. A browser test can help you see the dot, but it cannot repair physical pixel damage. For a closer look at a single defect, see how to check a monitor for dead pixels.

A patch or band changes with the background

Uneven brightness, color patches or a line that appears on several solid colors can point to a panel, connection or display-cable problem. If the mark also appears in other apps and on the device's startup screen, it is less likely to be caused by the test page or one app.

A faint image appears after you change the pattern

This may be temporary image retention, where a previous image remains faintly visible for a while. It can happen after a bright, static image has been displayed. If the mark fades after you show varied content or turn the screen off for a while, it may not be permanent. A persistent image on an OLED screen can be burn-in, which settings usually cannot reverse.

The screen looks uneven only at an angle

Some screens change brightness or color when viewed away from the center. A tinted viewing angle alone does not prove the panel is faulty. Check straight on and compare the same area at the angle you normally use the device.

The image looks normal, but taps fail

A visual check cannot confirm touch sensing. A display can show a clear picture while its touch layer has a dead zone or misses input. Use the Touch Screen Test to check for areas that do not register contact.

How to rule out simple causes

1. Remove surface marks. Clean the glass and check whether the spot moves or disappears. A fingerprint, dust under a protector or a scratch on the protector can resemble a screen defect.
2. Check a second app or screen. Open a plain page or the device's settings. If the mark appears only in one app, restart that app and check its display options before assuming the panel is damaged.
3. Turn off display adjustments temporarily. On Windows 11, check Settings › System › Display for Night light, color-related options and brightness settings. On macOS, open System Settings › Displays and temporarily turn off features such as True Tone or Night Shift if they are enabled. These options can change the screen's overall color, though they do not normally create a fixed physical pixel defect.
4. Check phone display settings. On an iPhone, look in Settings › Display & Brightness for True Tone and Night Shift. On Android, open Settings › Display and check options such as Night Light, color mode and adaptive brightness. Names can vary by phone maker.
5. Restart the device. A restart can clear a temporary graphics or app problem. Run the same patterns again afterward and check whether the mark remains in the same place.
6. Check for a screen protector or case pressure. If the protector is cracked, lifting or visibly damaged, remove or replace it only if you can do so safely. Do not pry at the screen itself.

When the display may need repair

A defect is more likely to be physical if it stays in the same position across different apps and test patterns, appears after a restart, or is visible before the operating system loads. A spreading dark blotch, colored vertical line, flicker or cracked glass also warrants prompt inspection. Back up important data while the device still works, then contact the manufacturer or a repair shop. Check warranty coverage before opening the device or paying for a repair.

If the screen was recently replaced, photograph the defect and note whether it changes with brightness or rotation. That information can help a technician distinguish a panel issue from a loose connection. Do not keep testing by pressing the affected area.

What a browser display test can and cannot show

A browser can display patterns that make visual problems easier to notice, but it cannot measure the panel's electrical condition or verify every pixel independently. The appearance can also depend on brightness, viewing angle, room lighting, color settings and the camera used to take a photo. Use your eyes to judge the display under normal conditions, and treat the test as a way to make the inspection more systematic.