Before you meet the seller
Look up the monitor model online. Check current retail prices, known issues, and any common defects. Bring a laptop or USB drive with our testing tools bookmarked. Ask the seller how long they have used the monitor and why they are selling it.
Physical inspection
Check the panel surface. Look for scratches, pressure marks, or dents by tilting the screen in the light. Shine your phone flashlight across the surface at a low angle to reveal scratches invisible from the front.
Inspect the stand and ports. Wobbly stands and damaged ports are expensive or impossible to fix. Test each input port (HDMI, DisplayPort, USB-C) if possible.
Look at the casing. Heavy scratches or cracks may indicate the monitor was dropped, which can cause internal damage.
Display tests to run
Dead Pixel Test: Cycle through white, black, red, green, and blue fullscreen. Look for any pixel that does not match. One or two stuck pixels in the corners may be acceptable at a good price, but dead pixels in the center are a dealbreaker.
Backlight Bleed Test: Display a black screen in a dimly lit room. Check for excessive light leaking from the edges. Some bleed is normal on LCD panels, but large bright patches are a problem.
Uniformity Test: Display 50% gray. Look for areas that are noticeably brighter or darker than the rest. Uniformity issues are unfixable.
Color Accuracy: Display red, green, blue, and white. Colors should look pure and even across the screen. Yellowing or tinting usually indicates age or settings issues.
Motion Test: Scroll text or move a window quickly. Excessive ghosting or smearing indicates slow pixel response, which matters for gaming and video.
What is acceptable
No used monitor is perfect. Minor IPS glow, a tiny amount of backlight bleed, and light scratches on the casing are normal wear. What you should reject: dead pixels in the center, severe backlight bleed, color uniformity issues, flickering, or intermittent signal drops.