Screen Test
Fill your whole screen with solid colors, gradients and pixel patterns to check for dead or stuck pixels, backlight bleed, banding and uneven brightness. Works on any Mac, MacBook, PC monitor or laptop screen — nothing to install.
17 screens. Click or press → for the next one, ← to go back, Esc to exit.
Solid colors
Patterns
Color cycle
Flashing warning: the cycle switches the whole screen between red, green, blue, white and black. Skip it if you are sensitive to flashing light. It is capped at 3 changes per second.
What each screen shows
| Screen | What to look for |
|---|---|
| White | Dead pixels (black dots), dust or debris under the glass, hairline cracks, and whether brightness is even from edge to edge. |
| Black | Stuck pixels (bright dots), backlight bleed glowing in from the edges or corners, and IPS glow. On an OLED, any light at all is a fault. |
| Red, green, blue | Each one lights a single subpixel color. A dot that stays dark on one of them but not the others is a single dead subpixel. |
| Cyan, magenta, yellow | Two subpixels at once. Cyan exposes a stuck red subpixel, magenta a stuck green, yellow a stuck blue. |
| Grays | 50% gray shows the "dirty screen effect", vertical banding and tint differences across the panel. 25% and 75% show the same in darker and brighter tones. |
| Gradients | Should be smooth. Visible stripes mean color banding — common on 6-bit panels and after heavy color correction. |
| Gray steps | The bottom two rows step one level at a time. If the first several near-black bars all look like pure black, shadows are being crushed; the same on the right for highlights. |
| Grid & circles | Circles should be round, not oval, and the white border should be visible on all four edges. A missing edge line means the picture is cropped (overscan). |
| Pixel patterns | Single-pixel lines and checkerboards. At native resolution they look like a flat, even texture. Moiré, shimmer or blur means the image is being scaled. |
| Text sharpness | Small text on white and on black, for comparing clarity and color fringing. |
How to check for dead and stuck pixels
- Clean the screen first — a speck of dust looks exactly like a dead pixel until you wipe it.
- Start the full-screen test and go through every solid color slowly, looking at the whole panel from a normal viewing distance.
- A dot that is black on every color is a dead pixel. A dot that stays lit in one color (often visible on black) is a stuck pixel.
- Note where it is and which colors it shows on. Most warranty and return policies count pixel faults by number and position, so a photo helps.
Testing a Mac or MacBook screen
Retina scaling. Macs usually run at a "looks like" resolution that is scaled from the panel's real one. The pixel patterns will show moiré in those modes — that is the scaling, not a fault. To see the panel's true sharpness, pick the "Default" size in System Settings → Displays before running the pixel patterns.
True Tone and Night Shift. Both shift the whole screen warmer. Turn them off before judging white, gray or color tint, or every Mac will look slightly yellow.
ProMotion (120 Hz). The refresh-rate readout measures how often the browser draws. Safari usually limits pages to 60 frames per second, so a 120 Hz MacBook Pro can read as 60 Hz there; Chrome reports the full rate.
Coating damage. On some MacBook models the anti-reflective coating wears into blotchy patches. These show best on the white and 50% gray screens with the brightness up, and look different from dead pixels: irregular smudges that do not wipe off.
Checking a laptop? Test its trackpad and keyboard too.
Trackpad testFAQ
What is the difference between a dead pixel and a stuck pixel?
A dead pixel gets no power and stays black on every color, so it is easiest to see on the white screen. A stuck pixel has one or more subpixels permanently on, so it shows as a bright red, green, blue or white dot — most visible on the black screen.
Can a stuck pixel be fixed?
Sometimes a stuck pixel clears on its own, and some people report success with gentle pressure through a soft cloth or long runs of rapidly changing colors, but none of these is reliable. A dead pixel cannot be fixed by software. If the screen is new, check the manufacturer's pixel policy and return window first.
How much backlight bleed is normal?
Most LCD screens show a little light at the edges on a black screen in a dark room, especially IPS panels, which also have a gray "glow" that changes with viewing angle. Bright patches you can see at normal brightness, in a lit room, or during dark movie scenes are worth raising with the seller. OLED screens should show no light on black at all.
Why does the refresh rate show 60 Hz on my 120 Hz or 144 Hz monitor?
Check the refresh rate set in your operating system's display settings first — many high-refresh monitors default to 60 Hz, or run at 60 Hz over an older cable. Battery-saving modes and some browsers (Safari in particular) also cap page animation at 60 frames per second, which this measurement reflects.