How to Check a Used Laptop or Monitor Screen Before You Buy

A used laptop or monitor can be a great deal, until you get it home and find a dead pixel in the middle of the screen. Most screen faults can't be fixed, and they're easy to miss in a shop or a stranger's living room. A ten-minute check with nothing but a browser will show you almost all of them, while you can still say no.

Before you start

You'll need the screen running with a web browser open. On a laptop that's easy. For a monitor, ask the seller to connect it to a computer, or bring a laptop and a cable. Turn the brightness all the way up, and if you can, turn the room lights down. Most screen faults hide in a bright room.

Dead and stuck pixels

Open the Dead & Stuck Pixel Check and go full-screen. Step through each color slowly and look across the whole screen, edges and corners included. A black dot on white is a dead pixel. A dot that stays red, green or blue on every color is a stuck one. One near the edge is easy to live with. One in the middle of the screen is something you'll see every day, so treat it as a reason to walk away or ask for a lower price. Dead vs. stuck pixels explains which kind sometimes clears up.

Burn-in

OLED screens and monitors that have spent years showing the same thing can keep a faint shadow of it, like a taskbar or a game's on-screen display. Run the Burn-in Check and look at the flat gray for soft shapes that shouldn't be there. Burn-in is permanent, so it's worth knowing about before you pay. Burn-in vs. image retention covers how to tell it from a ghost that fades on its own.

Backlight bleed and uniformity

On an LCD, the Backlight Bleed Check shows a black screen where light leaking around the edges stands out. A little glow in the corners is normal on most screens. Bright patches you can see from where you'd normally sit are not. Then run the Grayscale Gradient: visible steps or blotchy, tinted areas point to a tired panel. Backlight bleed vs. IPS glow helps you decide what counts as normal.

Laptops: move the lid

The cable that carries the picture runs through the hinge, and it wears with every open and close. With a bright test color on screen, open and close the lid slowly through its whole range. Flicker, lines or a screen that blanks at certain angles mean that cable is failing, and it usually gets worse. While you're there, turn the screen off and look at it in the light from an angle. Marks in the shape of the keyboard come from the lid being pressed shut, and scratches show up best this way too.

What's worth walking away from

Flicker, lines, burn-in and a dead or stuck pixel near the center are hard to fix and expensive to repair, so they're good reasons to pass or to bargain hard. A single pixel near the edge, or a little corner glow, is usually fine at the right price. If the screen is still under the maker's warranty, check how many faulty pixels it allows before it will replace the panel in the manufacturer policy comparison. Many brands accept a few, so a warranty won't always cover the one you found.