LCD Screen Tester
Test your display for dead pixels, stuck pixels, and uniformity issues
Click to cycle through all test patterns. Press ESC to exit anytime.
Grayscale Test
Click any shade to view fullscreen. Check for banding or uneven gradients.
Dead Pixels
Appear as black dots on bright colors. Permanently non-functional pixels.
Stuck Pixels
Appear as colored dots. Sometimes fixable with pixel-fixing videos.
Backlight Bleed
Light leaking from edges, visible on black screen in dark room.
Related Tools
What is LCD Screen Testing and Why Is It Important?
An LCD screen tester is a diagnostic tool that displays solid colors and patterns across your entire display to help identify dead pixels, stuck pixels, backlight issues, and other screen defects. Whether you're purchasing a new monitor, inspecting a used laptop, or troubleshooting display problems, running a comprehensive screen test reveals issues invisible during normal use.
Our free online LCD test works directly in your browser without any software installation. It cycles through pure colors including black, white, red, green, blue, and gray scales, making it easy to spot any pixel that doesn't display correctly. This type of testing is essential for anyone who relies on accurate screen performance for work, gaming, or creative projects.
Understanding Different Types of Pixel Defects
Dead Pixels
A dead pixel is a pixel where all three sub-pixels (red, green, blue) are permanently turned off. Dead pixels appear as tiny black dots that remain visible regardless of the image displayed. They're easiest to spot on white or bright backgrounds and represent a permanent hardware failure that cannot be repaired through software.
Stuck Pixels
Stuck pixels occur when one or more sub-pixels remain permanently lit. Unlike dead pixels, stuck pixels show a fixed color such as red, green, blue, or combinations like cyan, magenta, or yellow. Stuck pixels are sometimes repairable using pixel fixing software that rapidly cycles colors to unstick the transistor.
Hot Pixels
A hot pixel (or white pixel) occurs when all three sub-pixels are permanently on, creating a bright white dot. Hot pixels are most noticeable against dark backgrounds and can be particularly distracting during movie watching or gaming in dimly lit scenes.
Sub-Pixel Defects
Sub-pixel defects affect individual color components within a pixel. Since each pixel contains red, green, and blue sub-pixels, a single sub-pixel failure may only be visible when displaying certain colors. These subtle defects often go unnoticed until a thorough screen test is performed.
How to Properly Test Your LCD Screen for Defects
Prepare Your Display
Before running the dead pixel test, clean your screen thoroughly with a microfiber cloth. Dust particles and smudges can be mistaken for pixel defects. Also, let your monitor warm up for 10-15 minutes to ensure stable operation, as some pixel issues only appear once the display reaches normal operating temperature.
Test in Fullscreen Mode
Always run screen tests in fullscreen mode to eliminate distracting interface elements. Our tester automatically enters fullscreen when you click a test color. Examine the entire screen area systematically, including edges and corners where defects are commonly found.
Check All Color Channels
Cycle through primary colors (red, green, blue) and secondary colors (cyan, magenta, yellow) to test each sub-pixel channel. A pixel that appears normal on white might reveal defects when displaying pure red or green. The gray scale test helps identify uneven luminance and color accuracy issues.
LCD Panel Technologies and Their Common Issues
IPS Panels
IPS (In-Plane Switching) panels offer excellent color accuracy and wide viewing angles, making them popular for professional work. However, IPS displays are prone to IPS glow, a subtle brightening in corners visible on dark backgrounds, and potential backlight bleed along edges.
VA Panels
VA (Vertical Alignment) panels deliver superior contrast ratios and deep blacks compared to IPS. Common issues include black smearing during fast motion and potential color shift when viewed off-angle. VA panels are favored for movie watching and gaming where contrast matters most.
TN Panels
TN (Twisted Nematic) panels offer the fastest response times, making them ideal for competitive gaming. Trade-offs include limited viewing angles and less accurate colors. Color banding in gradients is more common on TN displays due to their 6-bit color depth with dithering.
OLED Displays
OLED screens don't use traditional backlighting, offering perfect blacks and pixel-level dimming. However, OLED panels can develop burn-in from static images and may exhibit uniformity issues where colors appear slightly different across the screen.
When Should You Run an LCD Screen Test?
Running a comprehensive monitor test is recommended in several situations to ensure your display meets quality standards and to document any defects for warranty purposes.
New Monitor Purchase
Always test new monitors immediately upon unboxing. Most manufacturers have dead pixel policies that allow returns within a specific timeframe if pixel defects exceed acceptable thresholds. Document any issues with photographs for warranty claims.
Buying Used Equipment
When purchasing second-hand monitors, laptops, or phones, run a dead pixel test before completing the transaction. Sellers may not disclose minor defects, and identifying problems beforehand helps negotiate fair pricing or avoid problematic purchases.
After Physical Impact
If your device has been dropped, bumped, or subjected to pressure, test the screen for new defects. Internal damage may cause pixel failures or backlight problems that aren't immediately visible but worsen over time.