Screen Tester

Screen Tester - Test Your Monitor for Dead Pixels

A comprehensive online screen testing tool that helps you check your monitor or display for dead pixels, stuck pixels, and other display issues. Test with solid colors (RGB), grayscale levels, and various patterns in fullscreen mode for accurate diagnostics.

How do I test my screen for dead pixels?

Testing your screen is simple:

1. Click 'Start Test' or choose any color (Black, White, Red, Green, Blue, etc.)
2. The screen will fill with that color
3. Look carefully for any pixels that are:
- Dead pixels: Always black/dark, even on bright colors
- Stuck pixels: Always bright or showing wrong color
- Hot pixels: Always bright white
4. Press Space to cycle through colors
5. Press F to enter fullscreen mode for better viewing
6. Use grayscale levels to check brightness uniformity
7. Try test patterns to check for alignment and geometry issues

Dead pixels are easiest to spot on white, red, green, and blue backgrounds.

What is the difference between dead and stuck pixels?

Dead and stuck pixels are different issues:

Dead Pixels:
- Always appear black or dark
- Completely non-functional
- Don't light up at all
- Usually cannot be fixed
- Most visible on white or bright backgrounds

Stuck Pixels:
- Appear as bright colored dots (red, green, blue, or white)
- Stuck in the 'on' position for one or more sub-pixels
- Most visible on black backgrounds
- Sometimes can be fixed by:
- Pixel-fixing software that rapidly changes colors
- Gentle pressure massage on the area
- Leaving the screen off for extended periods

This tool helps identify both types by testing all RGB channels.

What colors should I use to test?

Different colors reveal different problems:

Primary Colors (Best for dead pixel detection):
- Black: Shows stuck bright pixels, hot pixels
- White: Shows dead pixels (dark spots)
- Red: Shows dead or stuck red sub-pixels
- Green: Shows dead or stuck green sub-pixels
- Blue: Shows dead or stuck blue sub-pixels

Secondary Colors:
- Yellow (R+G): Tests red and green sub-pixels
- Cyan (G+B): Tests green and blue sub-pixels
- Magenta (R+B): Tests red and blue sub-pixels

Grayscale:
- Tests brightness uniformity
- Reveals backlight bleeding
- Shows color tinting issues

For comprehensive testing, cycle through all colors.

What are the test patterns for?

Test patterns help identify different display issues:

Grid Pattern:
- Check screen alignment
- Detect geometry distortion
- Verify pixel grid uniformity
- Test sharpness and clarity

Horizontal Lines:
- Check for horizontal banding
- Test vertical sync
- Detect scan line issues
- Verify even spacing

Vertical Lines:
- Check for vertical banding
- Test horizontal uniformity
- Detect column driver issues
- Verify pixel column alignment

Gradient:
- Test color transitions
- Detect color banding
- Check grayscale smoothness
- Verify gamma correction

These patterns are especially useful for calibrating monitors and checking for manufacturing defects.

How does Auto Rotate work?

Auto Rotate mode automatically cycles through all test colors:

1. Click 'Auto Rotate' to enable
2. Colors change every 2 seconds
3. Cycles through: Black → White → Red → Green → Blue → Gray → Yellow → Magenta → Cyan
4. Press 'A' on keyboard or click button again to stop
5. Great for continuous monitoring

This is useful when:
- You want to step back and view from different angles
- Testing multiple monitors simultaneously
- Demonstrating display issues to others
- Performing prolonged pixel tests

The rotation continues even in fullscreen mode.

Should I use fullscreen mode?

Yes, fullscreen mode is highly recommended for accurate testing:

Benefits:
- Fills entire screen with test color
- Eliminates browser UI distractions
- Provides true edge-to-edge testing
- Easier to spot pixels in corners and edges
- Better for backlight bleed detection
- More immersive testing experience

How to use fullscreen:
- Click the 'Fullscreen' button
- Or press 'F' on keyboard during test
- Press 'Esc' to exit fullscreen

Note: Fullscreen may not work on some mobile browsers. Use the largest view available.

Can this tool fix dead pixels?

No, this tool cannot fix dead pixels - it only helps detect them:

Dead Pixels:
- Usually permanent hardware failure
- Cannot be fixed by software
- Require screen replacement for true repair
- Some manufacturers have dead pixel policies

Stuck Pixels (may be fixable):
- Try pixel-fixing software that rapidly flashes colors
- Gentle pressure massage might help
- Leaving screen off for 24-48 hours
- Sometimes unstick on their own

If you find dead or stuck pixels:
1. Check your warranty or return policy
2. Many manufacturers allow returns for a certain number of dead pixels
3. Document the issue with photos
4. Contact manufacturer support

This tool is most valuable for:
- Testing new monitors before accepting delivery
- Checking used monitors before purchase
- Verifying warranty claims
- Regular maintenance checks

What keyboard shortcuts are available?

Keyboard shortcuts for efficient testing:

During Test:
- Space / → : Next color or pattern
- ← : Previous color or pattern
- F : Toggle fullscreen mode
- Esc : Exit test mode
- A : Toggle auto-rotate
- G : Show grid pattern
- H : Show horizontal lines
- V : Show vertical lines

These shortcuts allow you to:
- Test quickly without touching the screen
- Avoid causing stuck pixels from pressure
- Control from a distance
- Perform testing with one hand

All shortcuts work in both normal and fullscreen modes.

Key Features

• Test screen for dead and stuck pixels
• Full RGB color testing (Red, Green, Blue)
• Secondary colors (Yellow, Magenta, Cyan)
• Pure black and white tests
• Gray color for general testing
• 6 grayscale levels (10% to 90%)
• Grid pattern for alignment testing
• Horizontal and vertical line patterns
• Gradient pattern for color banding
• Fullscreen mode for accurate testing
• Auto-rotate through all colors
• Keyboard shortcuts for hands-free testing
• High contrast color name display
• Instructions visible on hover
• Works on desktop monitors, laptops, tablets
• Support for LCD, LED, OLED, AMOLED displays
• 100% client-side - no data collection
• No installation required
• Responsive design
• Dark mode interface support