#FF0000. Only the red sub-pixels are lit, so a red one that has died is a black dot here, and nowhere else is it as plain. A sub-pixel stuck on shows too: green turns its pixel yellow, blue turns it magenta. The page opens on this field.
1 of 6
Click, tap or press the right arrow for the next one. The left arrow goes back.
Red, step 1 of 6#FF0000. Only the red sub-pixels are lit, so a red one that has died is a black dot here, and nowhere else is it as plain. A sub-pixel stuck on shows too: green turns its pixel yellow, blue turns it magenta. The page opens on this field.
Green, step 2 of 6#00FF00. Green carries about 72 percent of a white pixel's light, which makes a dead green sub-pixel the easiest single fault to find: black here and a strong magenta on white. A red sub-pixel stuck on shows yellow against this field, and a blue one cyan.
Blue, step 3 of 6#0000FF. Give this field the longest look. Blue carries only about 7 percent of a pixel's light, so a dead blue sub-pixel hardly dims white at all, yet here it is a plain black dot. The field is dim, so lower the room lights.
Show all 28 colours and findings (25 more)
The six test colours, in order, continued
White, step 4 of 6#FFFFFF, every sub-pixel fully on. A pixel that has died completely is a black dot. With one sub-pixel gone the dot is tinted with what is left: cyan without red, magenta without green, faint yellow without blue. A pixel stuck fully on is invisible here.
Black, step 5 of 6#000000, every sub-pixel asked to go dark. Anything still glowing is stuck on: a red, green or blue point, or white when all three are stuck. Darken the room and give your eyes ten seconds. Dead pixels cannot be seen on this field at all.
Grey, step 6 of 6#808080, every sub-pixel at a part-way level. It is the one field where both kinds of fault show at once: a sub-pixel stuck on is brighter than its neighbours and a dead one is darker. Use it as a last sweep before you leave full screen.
Dark dots: sub-pixels that stay off 5
A black dot on every colourAll three sub-pixels of one pixel stay off. This is the dead pixel proper, which the reference sources call a dark dot defect. It shows on red, green, blue, white and grey alike and hides only on black. A colour-cycling tool is aimed at stuck pixels, not at this.
A black dot on red onlyThe red sub-pixel is dead and the other two work. On white the same pixel is a cyan dot giving about 79 percent of its neighbours' light, and on grey it is a darker blue-green speck. On green, blue and black it looks perfect.
A black dot on green onlyThe green sub-pixel is dead. It is the most visible single fault on white, where the pixel drops to a magenta dot with about 28 percent of its neighbours' light. It is the fault you are most likely to spot in a document before you run any test.
A black dot on blue onlyThe blue sub-pixel is dead. On white the pixel turns a yellow that still gives about 93 percent of full light, which is why this fault slips past a white-only check. Only the blue field makes it obvious.
A black line from edge to edgeA whole row or column has lost its connection to the driver board, a bonding fault that often follows a knock or flexing the panel in transit. It runs the full width or height, no software touches it, and the cure is a new panel.
Lit dots: sub-pixels that stay on 6
A red dot on blackThe red sub-pixel is stuck on. It vanishes on red and on white, where red should be lit anyway, and changes colour against the others: yellow on the green field, magenta on the blue one. It gives about 21 percent of a white pixel's light.
A green dot on blackThe green sub-pixel is stuck on, the brightest of the three at about 72 percent of a white pixel's light, so it is the hardest stuck fault to ignore in a dark scene. It shows yellow on the red field and cyan on the blue field.
A blue dot on blackThe blue sub-pixel is stuck on. At about 7 percent of a white pixel's light it is the dimmest stuck fault and needs a properly dark room. It shows magenta on the red field and cyan on the green one, and hides on blue and white.
A white dot on blackAll three sub-pixels are stuck on, which the reference sources call a bright dot defect or hot pixel. It shows on every field except white, and brightest of all on black, where it sits at full brightness in an otherwise dark picture.
A cyan, magenta or yellow dot on blackTwo sub-pixels of the same pixel are stuck on and the third works. Yellow means red and green are stuck, magenta means red and blue, cyan means green and blue. Note which, because a return form may count it as two faults, not one.
A dot you cannot find twiceNote where it sits the moment you see it, then step through all six colours and back. If the spot is clean on the second pass, note the date and try again tomorrow. A fault that comes and goes is hard to claim for, so photograph it while it shows.
Marks that are not pixel faults 4
A mark that a dry cloth removesDirt on the glass. Wipe with a dry microfibre cloth before you start, because a fleck of dust on a red field can pass for a dead sub-pixel. If the mark smears or moves, it was never part of the panel.
A dot that also shows in a screenshotA screenshot records the picture before it reaches the panel, so a panel fault can never appear in one. Take a screenshot, open it on another device and zoom in. A dot that is still there belongs to the image or the software, not to your screen.
Dots in your photos, not on the screenCamera sensors get defective pixels too, and they record light wrongly where a screen's pixels show it wrongly. Zoom or pan the photo. A sensor fault travels with the picture, while a screen fault stays fixed under the glass whatever you open.
A soft patch wider than a few pixelsA pixel fault has hard square edges and one colour. A cloudy patch with no clear edge is something else: uneven backlight, pressure on the panel, or wear. Plain white and plain black show those far better than this six-colour pass does.
Doing the check properly 7
How many pixels you are checkingA Full HD panel has 2,073,600 pixels and 6,220,800 sub-pixels. QHD has 3,686,400 and 11,059,200. A 4K UHD panel has 8,294,400 and 24,883,200. With that many points to look over, a careful pass takes minutes, not seconds.
Brightness up for colour, lights down for blackDead sub-pixels are dark marks on a lit field, so raise the screen's brightness and keep the room normally lit. Stuck ones are faint lights on black, so for that one step switch the lamps off and shade the screen from windows.
Nine squares, one at a timeDivide the screen into a three by three grid in your head. Clear one square fully before you move to the next, from about 30 cm away. A wandering eye skips whole regions of an eight-million-pixel panel. A square at a time, corners included, skips nothing.
Mark the spot, then change colourStick a small paper note on the bezel level with a suspect dot and another directly above it, so you can find it again without touching the panel. Watch that one pixel on every colour and write down where it shows. Match that against the dark and lit dots above.
Photograph the fault for a returnFill the frame with that part of the screen and include a corner of the bezel to show where it is. Cameras often draw wavy moiré bands across a photographed screen. If they cover the dot, change the distance or the angle slightly and shoot again.
Read the pixel policy before you countMakers differ. Some reject any panel with a single faulty sub-pixel. Others allow a set total, or a set number inside a small cluster, and may count a dark pixel differently from a stuck sub-pixel. If the shop's return window is still open, that is often the simpler route.
Phone OLED screens share red and blueThe table assumes three sub-pixels side by side in every pixel. Most phone OLED panels use a red, green, blue, green layout with one third fewer sub-pixels: every pixel has its own green, while red and blue are shared between neighbours, so the table fits those screens less exactly.
How this list was compiled: Written for this page. The colour each fault shows against each field, and every light percentage, were computed: a dead sub-pixel was set to 0 and a stuck one to 255 in the field's sRGB value, and light is relative luminance (0.2126 R + 0.7152 G + 0.0722 B on linear values, white as 100) from https://en.wikipedia.org/wiki/SRGB. Pixel and sub-pixel totals are width times height, times three for an RGB stripe panel. The names and causes of the faults (dark dot defect, bright dot defect or hot pixel, stuck sub-pixel, the edge-to-edge line of a tape automated bonding fault), the way makers' replacement policies differ, and defective pixels in camera sensors are from https://en.wikipedia.org/wiki/Defective_pixel. The red, green, blue, green layout of most phone OLED panels, with one third fewer sub-pixels, green mapped one to one and red and blue shared, is from https://en.wikipedia.org/wiki/PenTile_matrix_family. Moiré bands in photographs of screens are from https://en.wikipedia.org/wiki/Moir%C3%A9_pattern. All checked 2026-09-19. No pixel-fault class numbers from any standard are printed, because makers apply them differently. Licence: own work
How it works
A dead pixel test fills your screen with red, green, blue, white, black and grey so that one bad pixel stands out. What to look for names the fault, from a dead pixel to one stuck sub-pixel.
Read the full guide
How to check for dead pixels
Press Go full screen. Click, tap or press the right arrow for the next colour, and look over each one from corner to corner. Watch any suspect dot on all six colours, then match it to a line under What to look for.
Why this pixel test uses six colours
Every pixel is three sub-pixels: red, green and blue. Each primary lights one kind alone, so a dead sub-pixel is a black dot on its own colour. A dead blue one leaves white at about 93 percent of its light, which a white-only check misses. Black shows anything stuck on. Nothing flashes.
New screen? Run the six colours while the shop's return window is open, and note each fault's name for the form.
Need both hands for a magnifier? Tick Step on by itself, then pick 5 to 30 seconds under Every.
Questions and answers
Does this monitor dead pixel test work on a laptop, phone or TV?
Yes. It is a dead pixel checker and finder for any display with a browser: a monitor, laptop, LCD or OLED phone, or TV. Most phone OLED panels share red and blue sub-pixels between neighbours, so the named faults fit them less exactly.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel stays off: a black dot on every colour, hidden only on black. A stuck pixel, or one stuck sub-pixel, stays on: a red, green or blue point that shows best on black. The stuck pixel tool is for the stuck kind only.
How many dead pixels are acceptable on a new monitor?
There is no single number: each maker sets its own limit. A claim needs the fault's name, the colours it shows on and where it sits. Inside the shop's return window you may not need the maker's policy at all.
Dust or dead pixel: how can I tell?
Wipe with a dry microfibre cloth: a mark that moves or smears was dirt. Then take a screenshot and open it on another device. A defective pixel never shows in a screenshot, because the picture is recorded before it reaches the panel.