Black Screen Test: Check Backlight Bleed & Dead Pixels
Test your monitor, TV, or smartphone for IPS backlight bleed, OLED true black uniformity, dead pixels, and stuck subpixels in 100% fullscreen with zero distractions.
How to Test Your Screen in 3 Steps
Darken Your Room
Turn off overhead lights and draw the window shades. A dark environment eliminates reflections and makes backlight bleeding instantly noticeable.
Launch Fullscreen Black
Click the preview pad to enter true fullscreen. Wait 2 seconds for the mouse cursor and HUD toolbar to fade away completely.
Inspect Edges & Cycle Colors
Check the corners for yellowish or cloudy light leakage. Tap the Spacebar to cycle through red, green, blue, and white to catch dead pixels.
The Complete Guide to Backlight Bleed, Dead Pixels & OLED Uniformity
When buying a new gaming monitor, TV, or laptop, testing the display panel within the return window is vital. Understanding the physical causes of screen defects helps you determine whether an RMA replacement is justified.
IPS Backlight Bleed vs. IPS Glow
IPS panels are widely celebrated for superior color accuracy and viewing angles, but their physical design requires an LED backlight shining through liquid crystal layers:
- Backlight Bleed (Manufacturing Defect): Occurs when the monitor's outer bezel applies uneven physical pressure on the LCD panel, creating an opening where light from the backlight escapes along the edges or corners. Backlight bleed remains in the exact same spot regardless of your head position.
- IPS Glow (Normal Physical Property): Caused by the optical nature of the liquid crystal structure refracting light at wide viewing angles. IPS glow shifts, changes color, and moves as you move your head or sit further back from the monitor.
Dead Pixels vs. Stuck Pixels vs. Hot Pixels
Every display pixel consists of three subpixels (Red, Green, Blue):
- Dead Pixel: The transistor is permanently dead and receives zero current. It appears as an immovable black dot against white, green, or red backgrounds. Dead pixels cannot be repaired by software.
- Stuck Pixel: The transistor is frozen in an active electrical state, appearing as a bright, glowing red, green, or blue dot on a pure black screen. Stuck pixels can often be fixed using high-frequency pixel exercisers.
- Hot Pixel: A pixel that glows pure white across all subpixels when the screen is displaying black, often found in camera sensors and OLED panels.
OLED True Blacks and Near-Black 5% Grey Banding
Unlike LCDs, OLED (Organic Light Emitting Diode) and QD-OLED displays feature self-emissive pixels. When rendering pure black (#000000), the individual pixel turns completely off, emitting exactly 0 nits of light and producing an infinite contrast ratio. Testing with a 5% near-black dark grey screen reveals panel uniformity and vertical banding that is invisible on pure black.
Display Defect Types & Diagnostics Reference Matrix
Reference guide for identifying panel defects, recommended test colors, and repair options:
| Defect Type | Best Test Color | Visual Appearance | Panel Types Affected | RMA / Warranty Eligibility |
|---|---|---|---|---|
| Backlight Bleed | Pure Black (#000000) | Bright yellowish/white patches along bezel edges | IPS, VA, TN (LCDs with edge/direct LED) | Eligible if severe and visible in normal lighting |
| IPS Glow | Pure Black (#000000) | Silver or amber sheen that shifts as viewing angle changes | IPS panels only | Normal panel characteristic (Not eligible) |
| Dead Pixel | Pure White (#ffffff) | Tiny black dot that never lights up | All panels (LCD & OLED) | Subject to manufacturer ISO pixel policy (usually 3-5+ dead pixels) |
| Stuck Pixel | Pure Black (#000000) | Bright, single red, green, or blue subpixel dot | All panels (LCD & OLED) | Often fixable with pixel reviver tools |
| Dirty Screen Effect (DSE) | 50% Grey (#808080) | Cloudy, smudgy vertical or horizontal bands during panning | LCD TVs, large gaming monitors | Eligible if severe banding disrupts normal viewing |
| OLED Burn-In / Retention | 5% Grey, Red, Magenta | Faint ghost outlines of static UI elements (taskbar, logos) | OLED, QD-OLED | Covered under modern 3-year OLED burn-in warranties |
Frequently Asked Questions
Click the ⚡ Stuck Pixel Fixer button to activate our high-speed RGB strobing box. Drag the flashing box directly over the stuck pixel and let it cycle for 15 to 30 minutes. The rapid voltage switching frequently unsticks the liquid crystal transistor.
Screen Cleaning Mode fills your display with an undisturbed black or white canvas so that dust, fingerprints, and micro-scratches stand out clearly. You can safely wipe down your screen with a microfiber cloth without accidentally clicking browser links.
Our tool measures the interval between consecutive display paint cycles using the browser's requestAnimationFrame API over 120 frames to calculate your monitor's active refresh rate (e.g., 60Hz, 120Hz, 144Hz, 240Hz).
When inspecting for backlight bleed or dead pixels, a bright white mouse cursor creates optical glare that obscures subtle panel flaws. Moving your mouse brings the cursor and controls back immediately.