Dead pixel test

Every pixel is made of red, green and blue subpixels. Faults show up differently depending on the background:

Fault	What you see	Best background
Dead pixel	A black dot that stays dark on every color	White, red, green, blue
Stuck pixel	A red, green, blue or other colored dot that never changes	Black
Hot (bright) pixel	A white dot that is always lit	Black

Go through all the solid colors: black, white, red, green, blue, gray, yellow, cyan and magenta. A stuck green subpixel, for example, is invisible on green but obvious on black or red.

1. Clean the screen first. Dust looks like a dark dot; unlike a dead pixel, its shadow shifts when you look from the side.
2. Dim the room lights so reflections don't hide small dots.
3. Look at the screen in sections, top to bottom, at a normal viewing distance and then up close.
4. Note the position of anything suspicious and check it on several colors.

The test opens in full screen so toolbars don't hide the edges, and the mouse cursor is hidden so it can't pass for a stuck pixel. Turn on auto-cycle to step through the colors automatically, which leaves your hands free to move closer to the screen.

Solid colors find single pixels; the extra test screens find other problems:

• Gradients: smooth ramps from dark to light. Visible stripes (banding) or color tints in a gray ramp point to a low-bit panel, aggressive picture settings or a wrong color profile.
• Checkerboard: alternating black and white squares. Flicker, shimmering or uneven edges can reveal panel inversion artifacts, scaling at a non-native resolution, or overly strong sharpness settings.

While solid colors are up, also look for backlight bleed (bright patches near the edges on black), clouding (a patchy gray screen), burn-in (faint outlines of taskbars or logos on OLED screens) and lines (a full row or column of wrong pixels, usually a panel or cable fault).

Photosensitivity warning: the fixer shows rapidly flashing colors. Do not use it if you or anyone who can see the screen has photosensitive epilepsy or is sensitive to flashing light.

The fixer fills a square with flickering red, green and blue noise. Move and resize the square so it covers the stuck pixel, then let it run for several minutes, or longer if needed, and check the spot again on a black background. Rapid switching sometimes frees a subpixel that won't change state.

There is no guarantee: some stuck pixels recover, many don't. A dead pixel that stays black on every color can't be revived by software at all. Never press hard on the screen or use a pen or fingernail.

Manufacturers have dead pixel policies that state how many faulty pixels a display may have before it qualifies for repair or replacement. They differ between brands, product lines and the type of fault, and a bright pixel is often treated more strictly than a dark one. Check the policy for your exact model.

A retailer's return window is often more generous than the pixel policy, so test a new screen as soon as you unpack it and keep the box until you are satisfied.

• Windows and Linux: press F11 to toggle browser full screen if the button doesn't work; Esc exits.
• Mac: press Control+Command+F, or use the green window button.
• iPhone: Safari can't hide all its bars on iPhone. Rotate to landscape and scroll slightly for the largest area. Android: Chrome supports full screen; rotate to landscape for the biggest view.
• Colors look tinted: turn off Night light (Windows 11: Settings › System › Display), Night Shift or True Tone (Mac and iPhone), or the blue light filter on Android while testing, since they tint white and gray.
• TV: open the page in the TV's browser, or cast a browser tab to it.

Check your monitor's real refresh rate with the refresh rate test. For a plain bright screen to use as a light, open the white screen.