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Check for dead pixels, bright spots and dark spots
Professional Screen Testing
No software installation needed. Using browser fullscreen capability to provide pixel-perfect screen quality testing.
Pixel-Level Dead Pixel Detection
Multi-color fullscreen frame-by-frame scanning to precisely locate bright spots, dark spots, and stuck pixels. Supports 8+ solid color backgrounds with keyboard shortcuts, making every abnormal pixel visible.
Color & Greyscale Analysis
Full-spectrum testing covering color accuracy, gamut, greyscale, banding, and depth. sRGB/DCI-P3 gamut hidden pattern tests, 256-level greyscale transition evaluation to help judge your panel's true color performance.
20+ Testing Tools
Dead pixels, backlight bleed, greyscale, color accuracy, gamut, refresh rate, ghosting, blooming, HDR... covering every dimension of screen quality.
Free · No Download
All tools run in browser fullscreen. No downloads needed. Supports phones, tablets, laptops, monitors, and TVs.
Why Choose ScreenTester.io?
A professional screen testing platform with 20+ testing tools covering every quality dimension.
Pixel-Perfect Precision
Pure color fullscreen + F11 fullscreen mode ensures test patterns cover every physical pixel. Keyboard shortcuts and multiple test modes leave no defect undetected.
All Devices Supported
Phones, tablets, laptops, desktop monitors, TVs — any device with a screen. Just open the browser and test. No software or driver installation needed.
Complete Test Coverage
Dead pixels, backlight bleed, greyscale, color accuracy, gamut, refresh rate, ghosting, blooming, color depth, HDR — 20+ professional tools covering every display quality metric.
How to Get Started
Just three steps to fully understand your screen's quality.
Choose a Test Tool
Select dead pixel, backlight bleed, color accuracy, or other tests based on your needs. Beginners: start with dead pixel test — it's step one of any screen inspection.
Go Fullscreen (F11)
Press F11 to enter browser fullscreen. Pure color patterns will cover the entire screen. Use arrow keys or click to cycle colors and carefully examine every corner.
Review & Judge
Compare against quality standards: ≥1 bright pixel warrants a return; severe bleed warrants a return. Check our inspection guides for detailed criteria.
Core Testing Tools
Dead Pixel Test
Solid-color fullscreen frame-by-frame scan. Detects bright pixels (always-on), dark pixels (unresponsive), and stuck pixels (fixed color). The essential first step for any new screen.
Backlight Bleed
Pure black fullscreen in dark room to detect LCD backlight leakage and IPS Glow. Distinguishes fixed bleed (defect) from IPS Glow (normal characteristic).
Greyscale Test
256-level greyscale transition smoothness check. Reveals shadow crushing, highlight clipping, and color banding. Best used together with gamma calibration.
Color Accuracy
Standard color card comparison for bias diagnosis. ΔE<2 is professional grade; ΔE<3 is excellent for daily use. Quickly assess if your screen reproduces colors faithfully.
Color Gamut
sRGB/DCI-P3 hidden pattern gamut test. If you can see the hidden pattern, your screen covers that gamut. Instantly verify wide gamut claims.
Refresh Rate
Real-time frame rate detection to verify your panel's actual refresh rate. Claiming 144Hz but outputting 60Hz? This tool catches configuration issues.
Ghosting Test
Moving block test for response time and grey-to-grey transition speed. IPS ~1ms, VA ~4-15ms — dark scene ghosting is VA's biggest weakness.
Blooming Test
Mini LED local dimming precision test. Block/circle/subtitle patterns check halo overflow range. Higher zone counts produce less blooming.
Screen Troubleshooting Guide
Experiencing display issues? Use these guides for self-diagnosis:
Bright/Dark Spots on Screen
Solution:
2. Verify the same spot across multiple solid colors.
3. ≥1 bright pixel or ≥3 dark pixels — recommend return/exchange within return window.
4. Screenshot the defective pixel location as return evidence.
Screen Edge Light Leakage
Diagnosis Steps:
2. Distinguish IPS Glow (shifts with viewing angle) from true bleed (fixed position).
3. Assess severity at normal seating distance (50-70cm).
4. Severe bleed warrants return; IPS Glow is a normal characteristic.
Inaccurate / Shifted Colors
Troubleshooting:
2. "Vivid/Gaming" modes typically have poor accuracy — don't use as reference.
3. Grey backgrounds are most sensitive — green/red tint on grey indicates color accuracy issues.
4. For precise calibration, consider a hardware colorimeter (e.g., Spyder).
Wrong Refresh Rate / Stuttering
Common Causes:
2. Check cable — HDMI 2.0 only supports 4K@60Hz.
3. Laptops: confirm dedicated GPU direct connection (not iGPU output).
4. Some monitors require manually enabling high refresh in OSD menu.
Device Inspection Guides
Specialized testing workflows for different devices and panel technologies.
Laptop Screen Test
8-step laptop inspection flow. PWM flicker, gamut misrepresentation, panel lottery — all covered.
Mobile Screen Test
OLED burn-in, touch dead zones, PWM flicker — essential for used phone inspection.
TV Screen Test
Mini LED blooming, backlight bleed, MEMC verification. Must-do after new TV unboxing.
Monitor Screen Test
IPS/VA/OLED panel testing, PPI verification, G-Sync/FreeSync validation.
OLED Screen Test
Burn-in, PWM, ABL, black crush — comprehensive OLED-specific issue coverage.
LCD Screen Test
IPS bleed, VA ghosting, Mini LED blooming — complete LCD panel evaluation.
Use Cases
New Device Inspection
First thing after unboxing a new monitor, laptop, or phone — dead pixels, bleed, color accuracy. Find issues within the return window for easy exchanges.
Used Devices
Essential pre-purchase screen check. OLED: check burn-in. LCD: check bleed. Verify screen hasn't been replaced with a non-original panel.
Design & Color Work
Designers and photographers confirming screen color accuracy and gamut coverage. 100% sRGB is the minimum; wide P3 gamut is preferred. Test before calibrating.
Gaming Optimization
Gamers verifying refresh rate, response time, and VRR are working correctly. Catch the '144Hz advertised, 60Hz actual' problem before it's too late.
Frequently Asked Questions
Q.Are these tools accurate?
We render pure color patterns in browser fullscreen, directly driving GPU output to every physical pixel. Dead pixel and bleed detection works on the same principle as professional equipment. Color accuracy tests rely on visual comparison — for precise data, pair with a hardware colorimeter.
Q.Do they work on phones/tablets?
Yes. All tools are fully compatible with mobile browsers (iOS Safari / Android Chrome). For phone testing, turn off auto-brightness and manually set brightness to maximum for the most accurate results.
Q.How many dead pixels are acceptable?
Strictly speaking, any bright pixel is unacceptable — a constantly lit pixel on a black background is extremely visible. 1-2 dark pixels at the edges may be marginally acceptable. We recommend testing within your return window. Brand policies vary, but your consumer rights apply.
Q.How long does testing take?
Quick test (dead pixels + bleed): ~5 minutes. Full 8-step inspection: ~20 minutes. We recommend a quick test immediately after receiving the device, with a full inspection when time permits.
Q.Why must I test fullscreen?
Non-fullscreen mode leaves browser address bars, taskbars, and other UI elements covering screen edges — exactly where bleed and dead pixels are most common. Press F11 (desktop) or use the fullscreen button (mobile) to ensure complete coverage.
Q.Do I need a dark room?
Backlight bleed testing requires a dark room. Other tests are best done in normal lighting — since that's how you actually use your screen. Dark rooms amplify many details that are 'invisible during normal use,' which can trigger unnecessary concern.
Screen Testing Tips
Warm Up 15-30 min
Panel color temperature and brightness are unstable before warm-up. Wait at least 15 minutes after boot before color accuracy and greyscale tests for more reliable results.
Disable Enhancements
Turn off vivid mode, dynamic contrast, HDR, and other enhancements. Test in sRGB or Standard mode to avoid distortion.
Use Native Resolution
Non-native resolution triggers scaling that can hide dead pixels. Confirm system output resolution matches panel native resolution.
Use Proper Cables
DisplayPort 1.4 or HDMI 2.1 cables. Budget cables may not support high refresh/resolution, causing frame rate and resolution anomalies.
Dark Room for Bleed
Backlight bleed must be tested in total darkness. Pure black fullscreen, max brightness. Focus on corners and bezel junctions.
Judge at Normal Distance
After close-up inspection, step back to normal seating distance (50-70cm). Flaws only visible up close don't affect daily use.
Pixel-Perfect Precision for Every Screen
Whether you're inspecting a new display, testing a second-hand monitor, or diagnosing OLED burn-in, ScreenTester.io provides the most accurate screen testing tools — all free, all in your browser.