A used monitor or laptop can look fine on the desktop and still have dead pixels, uneven backlight, burn-in, color tint, or flicker. A five-minute screen check before buying can save you from a repair bill or an annoying defect you notice only after getting home.
Start with a Full-Screen Pixel Test
Open the MyDeviceScan Dead Pixel Test and switch to full-screen mode. Cycle through white, black, red, green, blue, yellow, magenta, and cyan. Look slowly across the screen from different angles. A true dead pixel usually appears as a black dot on bright backgrounds, while a stuck pixel may show as one color on several test screens.
If you are testing in a store or during a local sale, ask permission before opening a browser page. The test does not require installing software, which makes it easier to run on devices you do not own yet.
Check Backlight Bleed and Uniformity
Set the screen to black in a dim room. Some glow is normal on LCD panels, especially near corners, but large bright patches can be distracting during movies or dark games. Then switch to white and gray backgrounds to check for yellow tint, dark spots, or uneven brightness.
OLED screens need a different check. Instead of backlight bleed, look for burn-in: faint outlines of taskbars, app icons, navigation bars, or channel logos that remain visible on solid colors.
Used Screen Inspection Checklist
- Dead or stuck pixels - test multiple colors, not just white.
- Backlight bleed - check black screen in a dim environment.
- Burn-in - look for persistent shapes on OLED and older phone displays.
- Color tint - compare white and gray screens for uneven warmth or green/pink tint.
- Flicker - lower brightness and watch for visible pulsing or eye strain.
- Physical damage - inspect edges, pressure marks, scratches, and hinge pressure areas.
How Many Defects Are Acceptable?
For a new premium display, even one dead pixel can be unacceptable depending on warranty. For a used budget monitor, a single pixel near an edge may be tolerable if the price is low. The key is location. A stuck pixel in the center of the screen is far more annoying than one near a corner.
If you find multiple defects, negotiate the price or walk away. Screen replacement often costs more than the discount on a used device, especially for laptops, tablets, and phones.
Test the Real Use Case
After solid-color tests, open the kinds of content you actually use: text documents, dark video, a game menu, or a photo. Some defects are invisible during normal use, while others become obvious on text or dark scenes. If you are buying a monitor for design work, also check color consistency from left to right and top to bottom.
Finish by testing the device's native resolution and refresh rate in system settings. A monitor advertised as 144Hz but running at 60Hz may need a better cable, different port, or driver setting. Pixel tests catch panel defects; system settings catch configuration problems.