Screen Issues
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Free Screen Test Tool

A dead pixel is a pixel on your screen that has stopped working and remains permanently dark. A bright spot, on the other hand, is an area that glows even when it should be black. Backlight bleed is light leaking from the edges of an LCD screen, while screen burn-in leaves ghost images on the display. This free screen test tool helps you detect all of these issues in one test sequence: pure solid colors (white, black, red, green, blue, and gray) to expose dead pixels and bright spots; color gradients (red, green, and blue) to reveal banding, color tinting, and uniformity issues; test patterns (horizontal lines, vertical lines, grid, checkerboard, and RGB stripes) to find pixel rows, columns, or subpixel failures; and a motion blur test to evaluate your display's response time. By cycling through each test, you can quickly identify whether your display has any defects. Use this tool on laptops, monitors, tablets, or smartphones to get a clear picture of your screen's health. Click the preview card to auto-cycle through every test hands-free, so you can step back and inspect your screen from a distance. Whether you just bought a new device or want to check an existing one before returning it, this tool gives you an immediate and reliable diagnosis.

How to Use This Tool

  1. 1

    Click the preview card to start a fullscreen auto-cycle through every test. Close any applications or windows you do not want visible during the test.

  2. 2

    Use the "Next" and "Previous" buttons or the left and right arrow keys on your keyboard to cycle through each color. Press Space to advance one step.

  3. 3

    Look carefully at each solid color screen for any dark spots, bright spots, lines, color tinting, or uneven brightness. Do not rush — spend a few seconds on each color.

  4. 4

    Use the brightness slider at the bottom of the fullscreen view to reduce brightness. At lower brightness levels, backlight bleed and uniformity issues become much more visible.

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

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, it may be 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?
Dead pixels caused by complete transistor failure cannot be revived with software. However, if your pixel is stuck (showing one color instead of changing) rather than dead (showing nothing), pixel-fixing tools that rapidly cycle through colors may help. For truly dead pixels, screen replacement is the only solution.
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 brightness slider to 30–50% — severe backlight bleed becomes much more obvious at low brightness levels.
How many dead pixels are acceptable on a new screen?
Standards vary by manufacturer, but a common guideline allows up to 3 to 5 dead pixels depending on their location and the screen size. Apple, for example, will replace a MacBook screen if there are 6 or more dead pixels in a specific cluster. Check your manufacturer's warranty policy before the return window expires.
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.

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