By Display Expert TeamApril 9, 2026Updated November 4, 2026

Free Screen Test Tool

This free browser test fills a laptop, monitor, or phone with solid colors to show dead pixels, stuck pixels, bright spots, and backlight bleed. Black on every bright color means a dead pixel: use a return or panel replacement, not software. One fixed color means a stuck pixel: color-cycling software is an unofficial try, and Dell warns it can damage the panel.

A bright spot glows when the field should be black. Backlight bleed is light leaking from the edges of an LCD. The same run also includes color gradients, line and grid patterns, and a motion test. Click the preview card to auto-cycle, then step back and look. Use it the day a device arrives, and again before a return window closes.

How to run the test

1
Show solid colors. Open this page in the browser on the screen you want to test. Nothing to install. Start fullscreen and stop on solid white, then red, green, blue, and black.
2
Inspect each color. On white, red, green, and blue, look for a black pinprick or a dot of the wrong color. On black, look for a pixel stuck on one color or a soft glow. Wipe the glass first — dust moves, a panel defect does not.
3
Mark what you find. Write down where the speck sits and photograph the panel on the color that shows it. A screenshot of the desktop will not capture a panel-only defect. Black on every bright color means a return or panel replacement. One fixed color is the stuck-pixel case: unofficial color-cycling is sometimes tried, and Dell says those tools and screen pressure can damage the panel and may affect warranty.
4
Check bleed and the rest of the cycle. Use Next, Previous, the arrow keys, or Space to move through gradients, patterns, and the motion test. The test-image brightness slider dims only the webpage test image, not your device’s hardware brightness. Lower it in a dark room when you are looking for backlight bleed.

Solid Colors

White

Look for any dark spots, lines, or uneven brightness on a pure white screen.

← → Arrow keys to navigate | Space to advance | ESC to exit fullscreen

What to Look for on Each Color

Each test color reveals a different type of screen defect. Understanding what each color exposes helps you pinpoint the exact issue with your display.

Solid Colors

White

Look for any dark spots, lines, or uneven brightness on a pure white screen.

Black

Check for bright spots, stuck pixels, or light leakage bleeding through dark areas.

Red

Dead pixels may appear as tiny dark dots against the red background.

Green

Examine the entire screen for any abnormal bright or dark regions.

Blue

Blue helps reveal backlight unevenness and color uniformity issues.

Gray

Gray tests for subtle banding, uniformity problems, and faint bright spots.

Gradients

Red Gradient

Red gradient from dark to bright reveals color filter defects and uniformity issues in the red channel.

Green Gradient

Green gradient exposes panel uniformity issues and subpixel degradation in the green channel.

Blue Gradient

Blue gradient reveals backlight unevenness and blue channel defects more clearly than white.

Patterns

Horizontal Lines

Horizontal lines help detect dead pixel rows and uneven backlight across horizontal sections.

Vertical Lines

Vertical lines reveal dead pixel columns and gate driver issues in the vertical direction.

Grid

Grid pattern combines horizontal and vertical lines to catch any line defects across the full display.

Checkerboard

Checkerboard alternates black and white — look for any stuck or missing pixels in the grid.

RGB Stripes

RGB vertical stripes expose subpixel failures and color filter defects across individual color channels.

Motion Test

Motion Blur Test

Watch the moving block — any ghosting or trailing shadow indicates slow pixel response time. Ideal panels show a crisp, sharp block with no trail.

Common Screen Defects

These example images show how various defects appear on your screen.

Laptop and monitor on a white test field, with a black dead pixel and corner light leak — A white screen test makes a dead pixel and corner backlight bleed easy to see

Close-up of a dead black pixel on white, a bright stuck pixel on black, and light leaking at a screen corner — Dead pixel, bright stuck pixel, and backlight bleed look different up close

Person inspecting a solid red laptop screen and a solid black monitor in a dim room — Step back in a dark room and check each solid color for spots, lines, and uneven light

Black monitor with one small glowing white spot in the center — Bright spot on a black screen — a glowing point that should stay dark

Black laptop screen with milky light leaking along the bottom edge and corners — Backlight bleed on a black screen — light leaking along the bottom edge and corners

Gray monitor with cloudy patches and a slight color shift across the panel — Gray uniformity test — cloudy patches and a slight color shift across the panel

Frequently Asked Questions

Is this a free dead pixel test?

Yes. This screen test is free and runs in the browser on a laptop, monitor, tablet, or phone. There is no install and no account. Fullscreen solid white, red, green, blue, and black are the dead-pixel check. Black is where a stuck pixel or a bright spot shows up.

How do I test a laptop or phone screen for dead pixels?

Open this page on that device, in its browser, and run the colors fullscreen on the built-in panel. An external monitor only proves the computer can draw a color. It does not prove the laptop lid or the phone glass is clean. Dim the room, wipe the glass, then inspect white, red, green, blue, and black. On a phone, landscape plus Fullscreen hides more of the browser chrome. A thin system bar can remain.

What is the difference between a dead pixel and a stuck pixel?

A dead pixel stays black on white, red, green, and blue. A stuck pixel holds one color, usually easiest to see on black. Software does not revive a dead pixel — use a return window or panel replacement. Color-cycling software is an unofficial attempt for a stuck pixel only. Dell’s display pixel guidelines, last modified 12 October 2026, warn that pixel-fix software and pressing on the screen can damage the panel and may affect warranty. The stuck-versus-dead page compares appearance, fixability, and those warranty categories.

How do I know if I have a dead pixel?

A dead pixel appears as a small dark dot that never changes color, no matter what is displayed on the screen. To confirm, display a pure white background — a dead pixel will remain black against the white. It will also appear on red, green, and blue backgrounds. If the dot is invisible on a black background and shows one color there, it is a stuck pixel instead.

What is the difference between a dead pixel and a bright spot?

A dead pixel produces no light and appears as a dark or black dot. A bright spot, also called a light spot or white spot, glows on dark backgrounds where it should be dark. Bright spots are often caused by pressure on the screen, backlight bleeding, or dust trapped inside the display panel.

Can a dead pixel be fixed?

A dead pixel that stays black on every bright color cannot be revived with software. The path is a return window or panel replacement. If the pixel is stuck on one color, color-cycling tools are an unofficial attempt some people try. Dell’s pixel guidelines warn that those tools and pressing on the screen can damage the panel and may affect warranty.

What causes backlight bleed and how do I spot it?

Backlight bleed occurs when the backlight behind an LCD panel leaks light from the edges or corners, creating bright patches against dark backgrounds. To detect it, run the black screen test in a dark room. Reduce the test-image brightness slider to 30–50%. That dims the webpage test image toward black and does not change your device’s hardware brightness — severe backlight bleed becomes much more obvious at those levels.

How many dead pixels are acceptable on a new screen?

There is no single worldwide allowance. Dell’s public pixel guidelines, last modified 12 October 2026, allow up to five dark subpixels on many displays and zero bright pixels on Premium Panel Exchange models, with exceptions listed on that page. Other brands publish their own tables, or none. Check the policy for your model before the retailer return window closes.

What causes black or green lines on my screen?

Black or green lines running across your screen are typically caused by a fault in the display panel's gate driver circuitry, a damaged ribbon cable connecting the panel to the motherboard, or in rare cases, GPU issues. Black lines are usually dead pixel rows or columns, while green lines may indicate a stuck row of green subpixels or a connection problem. These lines do not fade on their own and usually require professional repair or panel replacement.

Why is my screen showing an orange or tinted color?

An orange or unusual color tint on your screen usually points to a color calibration issue, a damaged ribbon cable affecting color channels, or in OLED panels, pixel degradation. If the tint appears on a gray background, check your display color settings. If it persists across all colors and inputs, it may be a hardware issue with the panel's color filter or backlight. Try a different cable or input source first to rule out a connection problem.

What is the difference between screen burn-in and image retention?

Image retention is a temporary ghost image that fades after a few minutes when the display shows a different image — it is caused by charge buildup in the pixel capacitors. Screen burn-in, on the other hand, is a permanent defect where the ghost image remains visible regardless of what is displayed, caused by wear on the phosphors in plasma displays or uneven aging in OLED panels. Both appear as faint outlines of previously displayed content, but only burn-in is permanent and irreversible.