Dead Pixel Test — Check Your Screen for Dead & Stuck Pixels
This dead pixel test floods your whole screen with one solid colour at a time, so a pixel that is dead, stuck or permanently lit has nowhere to hide. Pick one of the eight swatches above, go fullscreen, and cycle through black, white, red, green, blue, magenta, cyan and yellow with a click or the spacebar. Anything that stays the wrong colour on a flat field is a defect.
How to test for dead pixels
Clean the screen first. On a white field, dust looks exactly like a dead pixel, and a good share of reported defects turn out to be dirt.
Then run the colours. Click any swatch to launch that colour fullscreen, or press Launch fullscreen to start on black. Click or press Space for the next colour, Esc to come back out. The cursor is hidden while the test runs so it cannot be mistaken for a defect. Scan in bands at your normal viewing distance, then again from about 30 cm for the corners.
Each colour is painted as a flat background, not a video, so there is no compression noise to confuse you: every physical pixel is driven to the same value, and anything that differs is the panel's own doing. The full monitor test adds uniformity, gradients, gamma and motion from the same page.
What each colour reveals
Black exposes stuck and hot pixels — a dot glowing red, green, blue or white on a dark field. White exposes dead pixels as black dots and dead sub-pixels as faintly tinted ones. Pure red, green and blue isolate one channel at a time, so a sub-pixel that fails only in green is invisible on white but obvious on a green screen. Magenta, cyan and yellow drive two channels at once and catch a missing sub-pixel most easily.
What this test cannot tell you
A dead pixel test cannot separate a defect from dirt or a scratch — that is your eye's job, and the reason to clean first. Nor can it say whether a fault sits in the panel or upstream: a whole dead row, column or vertical colour line is a driver or cable failure, not a pixel defect. Faint bright or dark patches on grey are panel uniformity, which the screen uniformity test covers, and a smear trailing behind moving objects is response time, measured by the monitor ghosting test.
Dead pixel vs stuck pixel
The difference is which state the pixel is frozen in, and two screens settle it. A dead pixel is permanently off: black on white, red, green and blue alike, because its transistor has failed and it gets no signal. A stuck pixel is permanently on: it glows against black and disappears into white.
Most real cases are sub-pixel faults. Each pixel is three sub-pixels and usually only one misbehaves. A dead sub-pixel shows on white, as a tiny cyan, magenta or yellow dot where one channel is missing. A stuck sub-pixel is the mirror image: a red, green or blue dot on black, gone on white. One rule sorts nearly every case: shows on white means something is dead; shows on black means something is stuck.
Testing a phone or tablet screen
Open this page on the device itself and tap a swatch — no app needed, and tapping cycles colours the way clicking does. On iPhone, Safari does not grant fullscreen to web pages, so the colour fills the viewport but the address and status bars stay; add the page to your home screen and launch it from there for an edge-to-edge field.
Turn off anything that tints the panel before you run a dead pixel test on a phone: auto-brightness, True Tone, Night Shift, blue-light filters and battery savers that dim the screen. A cast over the whole display is a setting, not a defect. On OLED, black is genuinely off, which makes one stuck sub-pixel glaring — but faint uneven patches on mid-grey are normal OLED behaviour. Judge dots, not gradients.
Stuck pixel fixer
Stuck pixels sometimes come back; dead ones essentially never do. If the dot is coloured on black and invisible on white, it is worth twenty minutes. If it is black on every colour, the transistor is gone and nothing displayed on screen will change that.
Two methods have real track records. Rapid RGB flashing cycles the sub-pixels many times a second to jolt a stuck one back into switching — JScreenFix claims around 80% within 20 minutes, while user reports run from an instant fix to nothing after a full night. Gentle pressure is the other: with black on screen, press lightly on the spot through a folded cloth for five to ten seconds. Both carry risk — hard pressure bruises the panel, long flashing sessions stress neighbouring sub-pixels — so time-box them. This page holds each colour steady so you can find a defect; it is a detector, not a fixer, and it deliberately does not flash.
How many dead pixels for a warranty claim
More than most people expect, and it depends on the brand and the tier of panel. Mainstream monitors are sold against the ISO 9241 pixel-fault classes, where a typical Class II panel is allowed a small number of bright and dark sub-pixel faults per million pixels before it counts as defective — so a single dot on a 4K screen of roughly 8.3 million pixels is usually inside spec.
Premium lines are the exception: several manufacturers publish zero-bright-pixel or premium-panel guarantees on professional and OLED models, where one always-on pixel is enough for a free exchange. Thresholds differ by model, so check the policy for your exact model number and whether bright and dark defects count separately. In practice a retail return inside the 14- to 30-day window beats a warranty claim for one pixel, so run a dead pixel test on a new display the day it arrives.
What causes dead pixels
Nearly all of them are manufacturing defects. A 4K panel carries about 8.3 million pixels and close to 25 million sub-pixels, each with its own thin-film transistor, and at that scale a handful fail — at the factory, or within the first months as a marginal one gives out. Nobody has driven that rate to zero, which is why warranty policies tolerate a few.
The main other cause is physical: a dropped phone, a laptop lid closed on a cable, a thumb pressed into the screen. Impact damage looks different — clusters or patches that spread rather than one isolated dot — and it is normally excluded from warranty. Software causes none of it; no update, driver or game reaches the transistor layer. If a mark appeared the day after an update, it was almost certainly already there.
Frequently asked questions
Can a monitor with a dead pixel get worse? Is it still worth buying?
A dead pixel does not spread — it is one failed transistor, not something that infects its neighbours. What can happen is that a panel with a weak batch of transistors produces more failures over time. The real warning sign is cause: if the dot came from a knock or pressure, the damage is physical and usually does grow. A monitor that left the factory with one dot in a corner will most likely stay exactly as it is.
What is the difference between a stuck pixel and a dead sub-pixel, and how do I tell which it is?
Check it on white, then on black. A dead sub-pixel shows up on white: the pixel has lost one colour channel, so it reads as a small tinted dot and vanishes into black. A stuck sub-pixel is the opposite — it glows red, green or blue on black and disappears on white. A fully dead pixel stays black on every field, including pure red, green and blue.
Should I RMA a monitor for one single dead pixel?
Usually not, unless your model carries a zero-bright-pixel or premium-panel guarantee. Mainstream warranties require several defective sub-pixels before a panel counts as faulty, so a single dot is normally refused. Phone support and ask before you ship anything. The exchange is also a gamble — the replacement can arrive with two or three defects in worse positions. If you are still inside the retailer's return window, that route is far more reliable.
Do stuck pixel fixer videos and programs like JScreenFix actually work?
Sometimes, on stuck pixels only — never on dead ones. Rapid colour flashing tries to jolt a sub-pixel that is frozen in one state back into switching. JScreenFix claims it clears about 80% of stuck pixels within 20 minutes; real reports range from an instant fix to nothing after running all night. Give it 20 to 30 minutes, repeat once, then stop. A dot that stays black on every colour is a dead transistor and will not respond.
Dead pixels appeared on my iPhone after a software update — can an update cause that?
No. Nothing in software reaches the transistor layer, so an update cannot kill a pixel. It can change what is on screen and make a defect you had not noticed obvious. Shape is the giveaway: real pixel defects are tiny and random. A semicircle, a blotch, or a mark near a button or edge is usually delamination or pressure damage instead — worth having inspected, since that is covered when there is no physical damage.
What could cause dead pixels? Could it be the user's fault?
Almost always a manufacturing defect, not anything you did. A 4K panel has roughly 25 million sub-pixels, each with its own transistor, and a few fail at the factory or in the first months. User-caused damage looks different: pressure and impact leave clusters, blotches or patches that spread, not one isolated dot. Heat and humidity shorten panel life slightly, but an ordinary desk in an ordinary room does not create dead pixels.