What a pixel defect is
A screen picture is made of a grid of small elements, and each one is built from smaller colored parts called subpixels, usually red, green and blue. The article on how pixels and subpixels form an image explains the structure. A pixel defect is a pixel, or one of its subpixels, that does not respond properly to the signal it is sent.
The terms are used loosely, but a useful working distinction is:
- Dead pixel. A pixel that stays dark. It never lights, whatever the picture does. It appears as a small black dot, most visible against a bright background.
- Stuck pixel. A pixel, or a subpixel, that stays lit in one color: red, green, blue, or sometimes white. It is most visible against a dark background.
- Hot pixel. A term some people use for a pixel that is always on at full brightness. It is closely related to a stuck pixel and the names are often interchangeable.
Many everyday “dead pixel” reports are actually stuck subpixels, since a colored dot is easy to mistake for a pixel that has died.
Why they happen
The causes depend on the panel type.
On LCDs, each subpixel is controlled by a tiny transistor that sets how much light passes through a layer of liquid crystals, as covered under how liquid crystals control light. If the transistor does not work, the subpixel can end up always open or always closed. A subpixel stuck open shows as a bright colored dot; one stuck closed shows as dark. A speck of dust or a flaw in a layer during manufacturing can have a similar effect.
On OLED screens, each subpixel makes its own light, so a failed subpixel is simply a dark point, and a subpixel that is stuck on is a drive-circuit problem. Because the emitters are organic materials that can age, there is also the possibility that a subpixel degrades unevenly over time, as the explanation of organic light emitters hints.
These faults are mostly the result of manufacturing at tiny scale: a typical screen has millions of subpixels, and making every one of them work perfectly is difficult. Occasionally a defect appears after some time in use, or after physical stress, but most are present from the start and do not spread or change much.
How to check
Fill the screen with a plain color and look at it from a normal distance, in a dim room:
- Black: stuck bright subpixels stand out as colored dots.
- White: dead pixels stand out as dark dots.
- Red, green and blue in turn: these help identify which subpixel is affected.
The test patterns article explains why such simple full-screen colors reveal so much. Keep the screen clean when checking, because a speck of dust or a smudge can look like a pixel defect. A defect stays in the same place and does not wipe away.
A camera or magnifier can help make out what you see, although a very close look can make a tiny fault seem larger than it is at normal viewing distance. Pixel density affects visibility: on a screen with very fine pixels, a single defect is smaller and often harder to see than on a coarser one.
Why makers tolerate some
It may seem odd that a new screen can be sold with a defect. The reason is mainly economic and practical. Producing panels with zero defective pixels is possible in principle but would drive up the cost, because many panels would be rejected. Makers therefore define an acceptance threshold and publish it as a policy. Some choose a stricter policy for premium products or for specific uses.
Policies vary widely, and this article does not give typical numbers because there is no single standard that all makers follow. Generally, a policy specifies things like:
- how many defective pixels are allowed in total,
- whether the limit depends on the type of defect, with bright dots usually treated as more serious than dark ones because they are more noticeable,
- whether location matters, with the center of the screen often treated as more important than the edges,
- whether clusters of defects close together are allowed.
Some makers also specify that a certain number of defective pixels is considered normal and not covered by warranty, while others allow a return or replacement if the number goes above a limit. The policy is typically found in the warranty terms or product documentation, and it is worth reading before purchase if a flawless screen matters to you. Retailers’ own return policies may be more flexible than the maker’s.
Where screen quality is tightly controlled for professional use, the topic overlaps with display quality control, which includes inspecting panels before they ship.
Can they be fixed?
Dead pixels, where something is physically broken, cannot generally be repaired by the user. Stuck pixels are sometimes reported to improve, but results are mixed and nothing is guaranteed.
You will find software tools and videos that flash rapidly changing colors on the screen in the hope of freeing a stuck pixel. Some people report success, and for some pixel states that are not permanent faults it may help. For most true hardware defects, it does nothing. These methods are generally harmless if used for short periods, though the flashing patterns can be unpleasant for people sensitive to flicker or with photosensitive conditions, so some caution is reasonable. Pressing on the screen with a finger or a tool is a method sometimes suggested, and it risks causing more damage. It is not advised.
Replacing the panel is the only reliable fix for a true defect, and because of how screens are built, repair is often not cost-effective, as discussed under screen repairability.
Putting a defect in perspective
A single dead or stuck pixel is a cosmetic issue for most people. It does not spread, and it does not indicate that the rest of the screen will fail. Whether it matters depends on how closely you look at the screen and what you use it for. Someone doing detailed image work might care about a stuck pixel in the middle of the image; someone watching video from the sofa may never see it.
If a screen has several defects, a cluster in a visible location or new ones appearing over time, it is reasonable to contact the seller or maker. Documenting the defect with a photo of a full-screen color before contacting them can make the conversation easier.