How to check screen defects before a return expires

A new monitor or laptop screen can look fine during ordinary use and still show a bright dot, a dark patch, uneven color, or flicker. Finding a defect before the return period ends gives you time to document it and ask the seller what they need.

Use the Display Test to inspect the screen with colors and other patterns. Then repeat any suspicious finding in normal use and take a photo that shows where it is.

Check the screen before the deadline

Open the Display Test on the screen you want to check. If you have more than one monitor, make sure the test is displayed on the one being inspected.
Look at the screen from a normal viewing distance, then move closer to check small details. Inspect the solid colors and other available patterns for dots, lines, patches, or uneven areas.
Check the whole panel, including the corners and edges. Look at white, black, red, green, and blue areas if available. A defect can be visible on one color and hard to see on another.
Note the location and appearance of anything unusual. For example, record that a tiny green dot stays near the upper-right corner on a black screen.
Repeat the check after cleaning the screen and restarting the device. If the defect remains, photograph it with a phone and keep the original image with your purchase information.

Use normal room lighting and your usual viewing position for the first pass. For faint marks, dim the room slightly, but avoid judging the screen only in complete darkness. A phone camera may add lines, bands, or color shifts that are not visible to your eyes, so compare the photo with the screen itself.

What the result means

A single pixel stays black or colored

A pixel is a tiny part of the image made from red, green, and blue subpixels. If one point stays dark on a bright pattern, it may be a dead pixel. If it stays bright or shows one color on a dark pattern, it may be a stuck pixel or subpixel. Check the same spot on several colors and in a normal app before deciding it is a panel fault.

A patch looks brighter or darker than the rest

Uneven brightness may come from the panel, backlight, or the way the screen is being viewed. Check the area on a full-screen white and gray pattern, then look at it from directly in front. If it remains in the same place and is noticeable during ordinary use, record it as a possible uniformity issue.

You see a line, flicker, or repeated band

A line that stays fixed in the same place across different colors may point to a display or connection problem. Flicker can also come from a refresh-rate setting, a cable, or a camera recording artifact. Confirm the symptom by looking directly at the screen, not only at a phone video.

Nothing unusual appears

The test did not reveal an obvious defect under the conditions you checked. It cannot promise that every fault is absent, especially one that appears only after the screen warms up, at a particular brightness, or while moving content. Use the device normally for a few days and check again if you notice something later.

Rule out settings and connection problems

Clean the screen gently. Turn the display off and use a clean, soft microfiber cloth. A speck of dust or dried residue can look like a pixel defect. Do not press hard or spray liquid directly onto the panel.
Use the screen's native resolution. On Windows 11, open Settings › System › Display and check Display resolution. On macOS, open System Settings › Displays and choose the recommended resolution or default option. Scaling changes the size of items, but the display should still be checked at its recommended resolution.
Check the refresh rate. On Windows 11, open Settings › System › Display › Advanced display and check the selected refresh rate. On macOS, open System Settings › Displays and check the available refresh-rate option if one is shown. Choose a supported setting and repeat the check if flicker or motion artifacts disappear.
Reconnect an external monitor. Turn the monitor off, reseat both ends of the display cable, and try a different port or a known-good cable if available. If possible, connect the monitor to another computer. A fault that follows the monitor is more concerning than one that appears only with a single cable or computer.
Restart and retest. Restart the computer, reopen the test, and check the same colors again. If the symptom appears only in one app, compare it with the desktop and another app before treating it as a screen defect.

When it is likely a hardware defect

A mark is more likely to be a panel defect if it stays at the same physical spot through different colors, apps, and restarts. A fixed line, a cluster of abnormal pixels, or a visible bright or dark patch that remains after cleaning also deserves attention. If the problem disappears when you change a cable or computer, investigate that connection instead.

Check the seller's return terms and the manufacturer's pixel policy before trying any repair. Policies can treat isolated pixels differently from clusters, and a browser test cannot decide whether a screen qualifies for replacement. For a useful record, include the purchase date, the test conditions, the location of the defect, and a clear photo. For more preparation, see how to test a monitor before the warranty deadline.

Take photos that show the problem clearly

Photograph the full screen first so the seller can identify the device and location of the issue. Then take a closer image of the affected area. Use the same test color that makes the defect easiest to see, keep the camera steady, and avoid using digital zoom. If the defect is difficult to capture, note that it is visible to the eye but not clear in the photo. Do not edit the image in a way that changes the appearance of the defect.

Finish the check well before the return deadline so you have time to contact the seller and follow its evidence instructions.