Dead Pixels, Stuck Pixels and Backlight Bleed: How to Test a New Monitor Before Your Return Window Closes

The best time to find a problem with a new monitor is the day it arrives. Most retailers give you a return window, often somewhere between two and four weeks, and returning a screen to the shop is almost always easier than going through a manufacturer's warranty. After that window closes, a dead pixel in the middle of your screen might just be yours to keep.

So here's how to test a new monitor properly. It takes about twenty minutes, and you don't need any special software beyond a full-screen color test like WakeMode's Screen Test.

Know what you're looking for

Every pixel on your screen is made of three tiny subpixels: red, green and blue. Most pixel faults come down to one of those subpixels misbehaving.

A dead pixel stays black no matter what's on screen. None of its subpixels light up. You'll spot it easily on a white or bright background.

A stuck pixel is stuck on one color, usually red, green or blue, because one subpixel won't turn off. It stands out against black and against colors that don't contain it.

A hot pixel, sometimes called a bright dot, stays white or very bright all the time. These are the most annoying in practice, because they jump out against anything dark.

Backlight bleed is different. It isn't a pixel problem at all. On LCD monitors, light from the backlight can leak around the edges of the panel, showing up as brighter patches near the corners or edges on a dark screen.

Set up before you test

A few minutes of preparation stops you from chasing problems that aren't there.

Clean the screen first with a dry microfiber cloth. A speck of dust looks exactly like a dead pixel, and you'll waste time worrying about it.

Let the monitor warm up for ten or fifteen minutes. Brightness and color can shift slightly as the panel reaches its normal temperature.

Set the brightness to where you'll actually use it, not maximum. Maximum brightness exaggerates bleed and makes perfectly normal panels look worse than they are.

Check every pixel with solid colors

Open a full-screen color test and go through black, white, red, green and blue, one at a time. On each color, scan the screen slowly in sections, left to right and top to bottom, the way you'd read a page. Don't rush. A single pixel on a 27-inch 4K monitor is tiny.

If you find a suspicious dot, check it on the other colors. A dot that changes color depending on the background is probably a stuck pixel. A dot that's black on everything is dead. If it disappears after you wipe the screen, it was dust. Your phone camera's zoom is handy for a closer look.

Check backlight bleed and glow

Turn the room lights off, or close the curtains, and show a full black screen. Sit at your normal viewing distance and look at the edges and corners.

Some light near the edges is common on LCD monitors, especially IPS panels. There are two different things to tell apart. Backlight bleed stays in the same place when you move your head. IPS glow is a soft shimmer that changes or shifts as you change your viewing angle. Glow is a normal trait of IPS panels. Strong bleed that's visible in normal use is worth returning.

One warning: don't judge bleed from a phone photo. Phone cameras boost dark scenes and make almost every monitor look terrible. Trust your eyes at your normal brightness.

If your monitor is OLED, there's no backlight, so there's no bleed. Instead, check a very dark gray screen for banding (visible stripes) or uneven tints.

Check uniformity and gradients

Show a full mid-gray screen. It should look like one even shade from corner to corner. Look for darker clouds, a color tint on one side, or corners that are noticeably dimmer. Then try a smooth gradient. You want a clean blend, not visible steps or stripes.

Perfect uniformity is rare, and some variation is normal, especially on cheaper panels. What you're looking for is anything you'll notice in everyday use, like a grayish cloud in the middle of a dark movie scene.

Check the pixel policy before you decide

Manufacturers accept that a few faulty pixels can happen, and most have a pixel policy that says how many they'll tolerate before they'll replace a panel. Policies often treat bright dots more strictly than dark ones, and some premium lines promise zero bright dots. Look up the policy for your exact model.

But remember the order of things: the retailer's return window is usually your easiest route, and it doesn't care about pixel policies. If you find something that bothers you, act within that window.

Can you fix a stuck pixel?

Sometimes. Stuck pixels occasionally recover after showing rapidly changing colors over that spot for a while. Dead pixels almost never come back. Avoid any advice that involves pressing or rubbing the screen. It can make things worse and may not be covered by warranty. And don't spend your whole return window trying fixes. If it's still there after a day or two, decide.

Buying used? Check a few more things

With a second-hand monitor, add a couple of checks. On OLED screens, look for burn-in by showing solid gray, red and blue, and watching for faint ghost shapes like taskbars or logos. Test every input you plan to use, and check the stand and ports for damage.

A quick checklist

1.       Clean the screen and let it warm up.

2.       Set your normal brightness.

3.       Check black, white, red, green and blue, section by section.

4.       Check bleed on black in a dark room.

5.       Check uniformity on gray and a gradient.

6.       Note anything you find with a photo and the date, then contact the retailer within the return window.

Twenty minutes now is a lot better than years of staring at one bright dot.