Monitor Test Online
A structured browser-based screen diagnostic tool to inspect your display for dead pixels, stuck subpixels, backlight bleed, and color uniformity.
Black Screen
Test Color Patterns
Inspect for stuck pixels (subpixels glowing red, green, or blue) and backlight bleed in a dark room.
Screen Settings
Display Text
Display a message in the center of your screen
How This Monitor Test Works
Screen defects like dead pixels, backlight bleed, and dirty screen effect (DSE) are often subtle and easily hidden by standard web pages or video content. This monitor test isolates your display with five calibrated full-screen color fields so your eyes can quickly spot irregularities. If you need a pure ambient screen for focus or lighting, you can also access our Black Screen tool and White Screen tool.
Black Field (Stuck Pixels & Bleed)
Highlights stuck subpixels that continuously glow red, green, or blue. When viewed in a darkened room, it reveals backlight bleed along frame edges.
White Field (Dead Pixels & Dust)
Highlights permanently unlit (dead) pixels, which show up as dark dots. Also illuminates surface dust and marks on the display glass.
Red Field (Red Subpixels)
Exclusively activates the red diodes across your panel to check red color fidelity, sub-pixel dropouts, and red channel banding.
Green Field (Green Subpixels)
Tests green subpixels. Because the human eye is most sensitive to green wavelength variations, green reveals panel tint anomalies faster than any other color.
Blue Field (Blue Subpixels)
Evaluates blue diode performance and checks for color temperature uniformity across wide viewing angles.
Pre-Test Preparation Checklist
- Wipe down your screen: Clean your display using a dry, lint-free microfiber cloth. Dust specks and microscopic smudges look identical to dead pixels under bright illumination.
- Warm up your monitor: Allow your display to run for 15 to 20 minutes before testing. Liquid crystals and LED backlights stabilize color temperature once warmed up.
- Dim room lighting: Turn off overhead lights or close window blinds when inspecting the black field to clearly distinguish backlight bleed from room reflections.
- Maximize to fullscreen: Click the fullscreen toggle in the preview area to ensure the color pattern extends completely edge-to-edge without browser borders.
- Step through all presets: Click each color preset one by one and scan your display from 12–18 inches away in a grid pattern.
Understanding Display Defects: Diagnostic Guide
Dead Pixels vs. Stuck Pixels
A dead pixel is a transistor that cannot receive power. It remains permanently black and is most visible against our white screen. A stuck pixel is a sub-pixel diode frozen in an "open" state, glowing continuously red, green, or blue against our black screen.
Backlight Bleed vs. IPS Glow
Backlight bleed is physical light leaking through bezel pressure points or gaps around the panel frame; it remains stationary regardless of viewing angle. IPS glow is a natural property of IPS panel liquid crystal structures that shifts and changes as you move your head.
Panel Technology Differences: IPS vs. VA vs. OLED
IPS panels deliver wide viewing angles and color accuracy, but are prone to corner glow. VA panels provide deep contrast ratios (3,000:1+), but may exhibit black smearing or gamma shift at extreme angles. OLED displays provide true zero-light black with no backlight bleed, but require testing for near-black chrominance uniformity.
What to Do If You Find a Screen Defect
1. Confirm with a microfiber wipe: Make sure the spot is not physical surface dust.
2. Attempt stuck pixel revival: If a subpixel is stuck on red, green, or blue, rapid color flashing software or extremely gentle localized pressure with a microfiber cloth wrapped around a stylus can occasionally restore diode conductivity.
3. Photograph the defect: Take a photo with macro focus and reduced exposure against both black and white backgrounds for proof.
4. Utilize retailer return windows: If your purchase is within the 14–30 day store return period, an immediate retailer exchange is significantly faster and more forgiving than manufacturer warranty claims.
Diagnostic Notice: This browser test serves as a visual inspection aid. It cannot repair broken hardware diodes or override manufacturer warranty thresholds.
Frequently Asked Questions About Monitor Testing
Can a software monitor test fix dead pixels?
Dead pixels are caused by physical diode failure or broken electrical connections and cannot be repaired by software. However, some "stuck" pixels (subpixels frozen on red, green, or blue) can occasionally be revived through rapid color cycling, although success is not guaranteed.
What is the difference between a stuck pixel and a dead pixel?
A dead pixel is permanently unpowered and appears as a tiny dark or black speck against light and colored backgrounds. A stuck pixel is a sub-pixel diode frozen in an active state, glowing continuously red, green, or blue against a dark background.
How can I take a clear photo of a dead pixel for warranty claims?
Display the solid background that best isolates the defect (white for dead pixels, black for stuck pixels), turn off your phone or camera flash, lower the camera exposure to prevent glare blowout, and photograph the screen perpendicular to the glass from 6–10 inches away with focus locked directly on the pixel.
How many dead pixels qualify for a warranty return?
Most display manufacturers adhere to the ISO 9241-307 Class 1 or Class 2 standard, which usually requires between 2 to 5 defective sub-pixels before replacing a monitor under warranty. Premium monitors occasionally carry a "Zero Bright Dot" guarantee. Always check your specific brand warranty policy.
What is the difference between IPS glow and backlight bleed?
To test the difference, change your viewing angle. If the glow shifts, dims, or moves as your head moves, it is normal IPS glow. If bright light remains fixed along the bezel edge regardless of angle, it is backlight bleed caused by physical bezel pressure.
Why should I clean my screen before running a dead pixel test?
Tiny specks of dust, lint, and dried smudges are the single most common cause of false-positive dead pixel reports. Wiping your screen with a dry microfiber cloth before testing ensures that you only inspect actual display diodes.
How often should I test my computer monitor?
You should always test a brand-new monitor or laptop immediately upon purchase while still inside the retailer's hassle-free return window, and test periodically if you notice unusual color tinting or persistent bright spots.