Click to Begin Inspection
Cycles through pure Black, White, Red, Green, and Blue screens. Look for any pixel that remains static or different from the surrounding field.
Web browsers cannot physically detect dead pixels via software code alone. Visually inspect the entire display surface during each color cycle. Clean your screen first to prevent confusing dust particles with defective pixels.
Active Screen Metrics
1.00x DPRHow to Identify Pixel Defects
A pixel whose transistor is permanently off. Stays completely black against a white or bright background.
One or more subpixels remain permanently on. Appears as a bright red, green, or blue dot across different backgrounds.
All RGB subpixels remain permanently on at full intensity. Appears as a bright white spot on black backgrounds.
Light leakage or cloudy patches around display corners and edges on LCD panels during dark screens.
Understanding Display Defects
How to Thoroughly Test Your Screen
- Clean the surface. Dust specks frequently look identical to dead pixels. Gently wipe your display with a microfiber cloth before starting.
- Dim ambient lighting. Backlight bleed, clouding (Mura), and dark-level subpixel anomalies are best spotted in a dimly lit room.
- Inspect from angles. View the panel directly and from slight side angles to differentiate IPS glow from permanent backlight bleed.
- Mark & Document. Click anywhere on the screen during fullscreen test to record exact pixel coordinates in your session log.
Honest Diagnostics & Privacy
- 100% Client-Side. All test pattern generation, canvas loupe magnification, and defect coordinates remain strictly in your browser memory.
- Zero False Claims. We never fabricate fake hardware defect counts or claim software guarantees for physical panel repairs.
- True Pixel Alignment. Patterns render at native 1:1 hardware pixel ratio using your Device Pixel Ratio.
- Session Report Export. Download your observation logs as a structured diagnostic summary.
Pixel Architecture & Defect Classification
What Is a Dead Pixel?
In modern flat-panel displays, a single image pixel comprises three separate red, green, and blue (RGB) subpixel chambers. Each subpixel is actuated by microscopic thin-film transistors (TFT) or discrete organic diodes. A dead pixel represents a state where all subpixel transistors within that specific triad have completely failed into an unpowered, inactive off-state.
Because zero optical luminance passes through or is emitted by a dead pixel, it appears as an indelible, sharply defined dark or black speck. Dead pixels are most conspicuous when viewing solid, high-luminance fields such as pure white, light gray, or vibrant pastel backgrounds. Because computer operating systems and graphic drivers cannot receive physical electrical feedback from defective panel nodes, human visual inspection during full-screen color tests remains the definitive method for defect verification.
What Is a Stuck Pixel?
Unlike a dead pixel that receives no power, a stuck pixel occurs when electrical current continuously energizes one or two subpixel cells, or when a liquid crystal molecule remains mechanically frozen in an open optical orientation. As a consequence, specific color filters allow backlight or emissive energy to radiate continuously without modulating in response to incoming image data.
Stuck pixels typically manifest as pinpoint dots of pure red, pure green, pure blue, or secondary combinations such as cyan, magenta, or yellow. They are most glaringly obvious on solid dark backgrounds and dark-mode software interfaces. Because a stuck pixel’s underlying transistor circuit still conducts electricity, rapid state-transition cycles (such as high-frequency subpixel strobing) can occasionally encourage the stuck crystal to resume standard switching behavior.
Comparative Analysis: Dead vs Stuck vs Hot vs Dim Pixels
Understanding visual symptoms helps determine the physical nature of screen anomalies.
| Defect Category | Visual Manifestation | Underlying Physical State | Optimal Detection Pattern | Software Exercise Potential |
|---|---|---|---|---|
| Dead Pixel | Permanent black or dark spot across all backgrounds | All subpixel TFT switches completely unpowered or broken | Pure White / Light Grayscale | None (Permanent) |
| Stuck Pixel | Static single color dot (Red, Green, Blue, Magenta, Yellow) | One or more subpixels continuously energized or crystal misaligned | Pure Black + Inverse RGB | Possible via Subpixel Strobe |
| Hot / Bright Pixel | Brilliant pure white dot at maximum light emission | All three RGB subpixels locked fully open simultaneously | Pure Black (0% Gray) | Low Probability |
| Dim Pixel | Lower brightness than neighbors; faint shadow appearance | Partial subpixel voltage delivery or physical diffuser obstruction | 50% Gray / Flat Tonal Screens | Unlikely |
| Subpixel Defect | Microscopic off-color hue visible only in close inspection | Isolated failure of an individual color cell in 4K/QHD density | Targeted Red, Green, Blue Screens | Possible for Stuck State |
How to Thoroughly Test Your Screen Online
Methodical Step-by-Step Display Diagnostic Procedure
Perform this structured 10-step visual audit to verify display health, isolate defective coordinates, and document panel anomalies accurately.
Clean the Panel Surface
Turn off the screen and gently wipe the panel with a clean microfiber cloth. Surface dust and skin oils can mimic subpixel defects under ambient light.
Confirm Native Resolution
Ensure your operating system is set to native 100% scaling and native resolution using our Resolution Checker to ensure 1:1 pixel rendering.
Launch True Fullscreen
Click Start Fullscreen Test. Fullscreen mode removes browser tabs, URL bars, taskbars, and OS window chrome for zero edge obstruction.
Audit Pure White Screen
Scan horizontally across the entire illuminated white field. Look for dark or black pinpoint specks indicating dead pixels or blocked light guide channels.
Audit Pure Black Screen
Inspect with room lights dimmed. Look for bright white (hot) pixels, glowing red/green/blue dots, and perimeter backlight bleed pools along the bezel.
Cycle Primary RGB Screens
Cycle through Pure Red, Pure Green, and Pure Blue fields using Space. A subpixel defect will stand out as an off-color dot.
Inspect Panel Corners & Edges
Users frequently miss edge anomalies. Systematically trace the extreme 10% perimeter and all four corners where mechanical bezel stress is highest.
Use the Built-in Loupe Magnifier
Press M to open the real-time 8x canvas loupe over suspicious spots to verify whether an entire pixel or single subpixel is affected.
Mark Defect Coordinates
Click directly on any defect to open the coordinate marker. Categorize the defect, add notes, and store precise X/Y pixel coordinates in your session log.
Primary Inspection Colors & Subpixel Isolation
No single test color can expose all pixel defects. Because an image is produced by mixing varying intensities across red, green, and blue subpixels, each solid testing field targets specific physical operational states of the panel.
Pure Black Screen
Commands all subpixels to block light (LCD) or turn off (OLED). Exposes hot white pixels, stuck RGB subpixels, and backlight bleed.
Pure White Screen
Commands all subpixels to 100% maximum luminance. Highly effective for detecting dead (black) pixels and severe panel tinting.
Pure Red Screen
Isolates the red subpixel channel. A dark speck on red reveals a dead red subpixel; a green/blue dot indicates an erroneous cross-channel activation.
Pure Green Screen
Human vision is most sensitive to green wavelength luminance. Green screens quickly reveal dark or stuck green subpixels.
Pure Blue Screen
Isolates blue subpixels. Critical for evaluating organic subpixel health on OLED displays, where blue emitters experience the highest operational stress.
Display Uniformity, Backlight Bleed & IPS Glow
Backlight Bleed vs IPS Glow
Many users confuse IPS glow with backlight bleed. While both manifest as unwanted corner luminance on dark screens, their underlying physics and implications are fundamentally distinct.
Occurs when the structural bezel applies uneven pressure or when optical adhesive gaps allow light from edge LEDs to escape around the display frame. Backlight bleed remains in a fixed position and does not diminish when you change your viewing position.
An inherent optical property of In-Plane Switching liquid crystal alignment. Off-axis light dispersion produces a subtle silver or amber sheen across screen corners when viewed from short distances. IPS glow changes in intensity and shifts position as you move your head or increase your viewing distance.
Screen Uniformity & Mura Clouding
Screen uniformity quantifies how evenly brightness (luminance) and color temperature (chromaticity) are distributed across the active panel area. In a consumer display, slight variances from center to edge are normal, but severe variations can disrupt color-critical graphic editing and video workflows.
Mura (from Japanese for unevenness) refers to subtle, cloudy patches or localized tinting visible on flat mid-tone fields (such as 25% or 50% gray). It is caused by minor manufacturing discrepancies in liquid crystal layer thickness, optical diffuser plates, or localized backlight thermal buildup. Testing across our 20%, 40%, 60%, and 80% flat grayscale patterns reveals any distracting clouding characteristics.
Grayscale, Banding & Sharpness Diagnostics
Grayscale Steps & Gamma
Our Grayscale 16-Step and 32-Step patterns verify tone reproduction. A well-calibrated panel should clearly separate deep shadow blocks (0% vs 3%) without "black crush," and separate peak highlights (97% vs 100%) without "white clipping." Compare with our dedicated Contrast Checker for comprehensive dynamic range testing.
Color Banding & Bit-Depth
Smooth horizontal and vertical color gradients test internal signal bit-depth (e.g., 6-bit+FRC, true 8-bit, or 10-bit). Abrupt vertical lines or stepped artifacts within a continuous gradient indicate signal quantization limits, aggressive GPU color compression, or internal LUT dithering constraints.
Text Sharpness & 1px Grid
Our 1px Geometry Grid and Text Sharpness matrix test native pixel alignment and subpixel antialiasing (such as Windows ClearType or macOS font smoothing). Blurring, color fringing around letters, or moiré wave patterns indicate non-native display scaling or subpixel layout mismatches (e.g., BGR vs RGB, or OLED subpixel fringing).
Display Panel Technologies Compared
OLED & QD-OLED
EmissiveIndividual self-lit pixels provide true 0-nit black levels and high dynamic range. When testing OLEDs, focus on near-black uniformity (1%–5% gray) to check for vertical manufacturing banding. Use solid colors to inspect for temporary image retention or subpixel aging.
IPS Panels
TransmissiveRenowned for wide viewing angles and consistent color fidelity. Testing should focus on distinguishing benign off-axis IPS glow from true mechanical backlight bleed along corners and frame edges during black screen patterns.
VA Panels
High ContrastVertical Alignment offers superior native contrast ratios (typically 2500:1 to 4000:1). Test for off-axis gamma shift and dark-level response transitions. Check for clouding patches across 50% gray fields.
TN Panels
Legacy SpeedTwisted Nematic panels offer rapid pixel response but narrow vertical viewing angles. When testing TN screens, maintain an exact perpendicular eye line to prevent vertical color inversion from interfering with defect checks.
OLED Burn-In vs Temporary Image Retention
On organic self-emissive displays (OLED, AMOLED, QD-OLED), users must differentiate between harmless temporary image retention and permanent burn-in.
Temporary Image Retention (Ghosting)
Temporary retention is an ephemeral electrical charge bias across recently driven organic diodes. After displaying static elements (e.g., bright HUDs or spreadsheets) for prolonged periods, a faint shadow may linger on mid-gray screens. This resolves naturally after turning off the panel or executing the built-in short pixel refresher cycle.
Permanent Burn-In (Subpixel Degradation)
Permanent burn-in represents irreversible physical degradation of organic light-emitting subpixels caused by thousands of cumulative hours of high-luminance static graphics. The degraded subpixels permanently produce lower peak luminance than surrounding pixels, leaving static outlines visible across uniform color screens. Software tools cannot repair physical emitter wear.
Used & Refurbished Monitor Purchase Checklist
Field Inspection Guide for Second-Hand & Refurbished Purchases
Before accepting or finalizing payment for a used monitor, connect a laptop or source device and execute this complete pre-purchase verification.
Run the 5-color Quick Test. Check particularly near the screen center where defects cause maximum visual distraction during daily work.
Display Pure Black in dimmed lighting. Look for severe corner flare or pinched edges that suggest drops, frame warping, or improper repairs.
Display neutral gray to immediately expose surface scratches on anti-glare coatings, internal diffuser stains, or localized Mura patches.
Confirm the panel negotiates native resolution with our Resolution Checker and check maximum refresh rates using our Refresh Rate Checker.
Test all DisplayPort, HDMI, and USB-C inputs. Ensure signal handshakes remain stable without screen blackouts or flickering artifacts.
Adjust height, swivel, and pivot mechanisms. Feel the rear power casing for excessive heat buildup or unusual buzzing/coil whine from the power supply.
Screen Troubleshooting & Anomaly Isolation
Is It a Dead Pixel or Surface Dust?
Airborne dust specks and microscopic liquid residue commonly look identical to dead pixels at first glance. To reliably distinguish them:
- Parallax Effect: Move your head left to right while observing the anomaly. Surface dust sits on the outer glass surface and shifts position relative to the pixel grid beneath. A true dead pixel remains strictly anchored to the subpixel matrix.
- Geometry Under Magnification: Using our 8x loupe tool or a smartphone camera macro mode, a real subpixel defect exhibits rigid, rectangular pixel grid geometry. Dust particles show irregular organic contours.
Panel Defect vs GPU / Driver Artifact
Not every screen anomaly stems from panel hardware. Before filing a warranty claim, rule out upstream software and transmission issues:
- Cable Integrity: Loose or out-of-spec HDMI/DisplayPort cables can generate sparkling colored pixel noise across the screen. Re-seat or swap cables.
- GPU Memory Artifacts: Overclocked or failing VRAM generates shimmering clusters of pixels that move with application windows. Real panel defects stay permanently fixed in physical coordinate space regardless of window movement.
Warranty Policies & Return Decisions
When purchasing a new monitor, always test the screen immediately upon unboxing. Understanding commercial return windows and manufacturer pixel fault policies protects your consumer rights.
Retailer Return Window
Most major retailers offer a 14 to 30-day "no-questions-asked" return or replacement window. If you spot any dead or stuck pixels in your primary viewing area, returning through the retailer is faster and simpler than filing a manufacturer warranty claim.
Manufacturer Defect Policies
Each manufacturer establishes specific dead and stuck pixel thresholds for warranty service, which often depend on panel grade, resolution, and product tier. Some premium models include Zero Bright Dot (ZBD) guarantees during the initial warranty period, while others require multiple defective subpixels before qualifying for replacement.
Defect Location Matters
A dead pixel located in the center quadrant of the display is significantly more disruptive than one located along the outer edge. Use our session Defect Log to export coordinate reports for your retailer or manufacturer support tickets.
Diagnostic Capabilities & Limitations
What This Online Tool Can Accurately Test
- Provides 100% native 1:1 Device Pixel Ratio rendering directly to your display.
- Generates 25 high-precision color fields, grayscale ramps, gradients, and 1px grids.
- Offers real-time canvas loupe magnification up to 16x for subpixel analysis.
- Logs exact hardware pixel coordinates and defect types for warranty documentation.
- Provides targeted stuck-pixel color exercise routines with safety timers.
What Software Alone Cannot Determine
- Browsers cannot automatically detect physical pixel failure without human visual verification.
- Cannot measure physical colorimeter metrics (Delta E color accuracy, absolute candelas/nits).
- Cannot guarantee electrical repair of broken transistors or burnt-out emissive diodes.
- Does not replace professional hardware color calibration tools (colorimeters and spectrophotometers).
Frequently Asked Questions
What is a dead pixel?
A dead pixel is an individual picture element on an electronic display whose controlling thin-film transistors (TFT) or emissive diodes have failed into an unpowered, inactive state. On backlit LCD panels (including IPS, VA, and TN) and emissive OLED displays, a dead pixel remains permanently dark and unlit, making it most noticeable as a tiny black speck against pure white or bright solid backgrounds.
What is a stuck pixel?
A stuck pixel occurs when one or two subpixels (Red, Green, or Blue) remain locked in an energized state, allowing light to pass continuously through those specific color filters regardless of the requested image signal. Stuck pixels appear as constant, vivid pinpoint dots of red, green, blue, cyan, magenta, or yellow, and are most visible against dark or contrasting solid backgrounds.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel is completely non-functional and permanently dark (black) because its subpixels receive no power. A stuck pixel is actively receiving power or has a misaligned liquid crystal cell, causing one or more colored subpixels to stay permanently turned on. While dead pixels cannot be fixed via software, some stuck pixels can occasionally return to normal operation after rapid color stimulation or thermal stabilization.
What is a hot or bright pixel?
A hot or bright pixel is a full pixel where all three primary subpixels (Red, Green, and Blue) are stuck at maximum brightness simultaneously. This creates a brilliant, pure white dot that stands out sharply against solid black or dark-themed backgrounds.
What is a subpixel defect?
Each physical pixel consists of three or four individual color components called subpixels (typically Red, Green, and Blue, or RGBW). A subpixel defect occurs when only a single subpixel fails or sticks rather than the entire pixel cluster. Because modern high-density screens pack millions of pixels into tight spaces, subpixel defects appear as tiny color imbalances visible only on specific color test screens.
How do I test my monitor for dead pixels?
To test your monitor, clean the display surface with a microfiber cloth, set your operating system to the display's native resolution, and launch the fullscreen test. Methodically cycle through primary solid colors (Pure Black, Pure White, Pure Red, Pure Green, and Pure Blue). Carefully scan the entire panel from top to bottom and corner to corner on each color, noting any static dots that do not match the background.
Which colors are best for finding dead and stuck pixels?
Pure White is optimal for spotting completely dead (black) pixels and dim subpixels. Pure Black is best for locating bright white (hot) pixels, stuck colored subpixels, and backlight bleed. Pure Red, Pure Green, and Pure Blue isolate individual subpixels to expose single-channel stuck or dead subpixel anomalies.
What is backlight bleed?
Backlight bleed is a hardware characteristic of liquid crystal displays (LCDs) where light from the edge-lit or direct-lit CCFL/LED backlight assembly escapes around the perimeter, corners, or bezel housing. It appears as fixed, cloudy light pools along the display edges that remain visible during dark scenes and do not change with viewing angle.
What is IPS glow and how does it differ from backlight bleed?
IPS glow is an inherent optical property of In-Plane Switching (IPS) panel architecture caused by off-axis light dispersion through the liquid crystal matrix. Unlike backlight bleed (which is localized light escaping through panel seams), IPS glow appears across broad corners when viewing dark screens from an angle and visibly shifts, dims, or moves as you change your physical viewing position.
How do I test a monitor for backlight bleed?
Set the monitor to a normal viewing brightness rather than an unusually high or low setting, dim the room lights to eliminate ambient glare, and display a fullscreen pure black pattern. View the monitor directly perpendicular from a normal viewing distance (at least arm's length). Fixed bright flare along panel bezels that does not shift when shifting your head indicates backlight bleed.
What is screen uniformity?
Screen uniformity refers to the consistency of luminance (brightness) and chromaticity (color temperature) across the entire active display area. Poor uniformity results in darker corners, center hot spots, or localized color tints (e.g., warmer or cooler patches) when viewing uniform white, gray, or solid-color backgrounds.
What are Mura and clouding?
Mura (a Japanese term for unevenness) refers to subtle, blotchy, or cloudy luminance variations across an LCD or OLED panel caused by slight manufacturing variations in substrate thickness, liquid crystal density, or light guide plate diffusion. It is most noticeable on mid-tone gray test patterns (such as 25% or 50% gray).
How do I test an OLED or AMOLED monitor?
Test OLED and AMOLED screens using near-black test patterns (1%, 3%, and 5% gray) to evaluate low-luminance uniformity and near-black vertical banding. Pure black can help you inspect whether individual pixels remain visibly illuminated when they should be off, while solid color patterns help check for subpixel aging, tint shifts, or image retention artifacts.
What is the difference between OLED image retention and permanent burn-in?
Image retention (ghosting) is a temporary visual artifact where faint ghost images of static UI elements linger for a short time after high-contrast display usage, resolving naturally as the panel rests or runs a pixel refresher cycle. Permanent burn-in represents irreversible non-uniform degradation of the organic emissive subpixels caused by cumulative static exposure, resulting in permanent ghost outlines.
Can a stuck pixel be fixed with software?
Some temporarily stuck subpixels caused by minor liquid crystal alignment hesitation can occasionally recover through rapid subpixel exercise routines that trigger high-frequency color cycling. However, software routines provide no guarantee of hardware recovery, and completely dead transistors cannot be repaired through software code.
Should I physically press or massage a stuck pixel?
We strongly advise against pressing, rubbing, or applying mechanical pressure to modern LCD or OLED panels. Applying physical force can damage the delicate internal layers, harm adjacent functional subpixels, and may affect warranty coverage.
How do I distinguish a dead pixel from a dust particle?
Dust particles rest on the exterior glass or anti-glare coating and change their parallax position relative to the underlying pixel grid when you shift your viewing angle. A genuine dead pixel is embedded within the subpixel layer, remains precisely stationary regardless of viewing angle, and exhibits sharp, square geometric subpixel boundaries under magnification.
How should I test a used or refurbished monitor before purchasing?
Run a systematic inspection: (1) Check solid colors for dead/stuck pixels; (2) Display pure black in dim lighting to check backlight bleed and corner glow; (3) Display 50% gray to inspect for clouding, scratches, or uneven wear; (4) Display fine 1px grid patterns to check whether fine pixel-level patterns render as expected at the display’s native resolution; (5) Inspect physical ports, bezel seals, and stand stability.
Can this online test automatically detect dead pixels without human inspection?
No. Web browsers and operating systems only transmit image framebuffers to the display controller; they lack optical sensors or physical feedback mechanisms to know whether a physical pixel's transistor actually emitted light. Visual inspection by the user in fullscreen mode is essential for identifying physical display defects.
When should I return a monitor due to pixel defects?
Monitor return policies vary significantly by retailer and manufacturer pixel-defect policies. If a defect is located in the central viewing zone, remains highly visible during normal workflow, or if your retailer offers a standard return window (typically 14 to 30 days), consider returning or exchanging the display immediately.
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