Uniformity
Color & Dynamic Range
Motion & Refresh
Text & Sharpness
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PROFESSIONAL SCREEN DIAGNOSTICS
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The Brightness & APL test evaluates your display’s peak luminance and Average Picture Level (APL) handling. Modern displays, especially OLEDs and Mini-LEDs, manage their light output dynamically based on how much of the screen is white.
🔲 Window Size (1–100%): Use the slider to adjust the size of the white window. A 100% (FULL) window tests full-field sustained brightness, while smaller windows (1%, 5%, 10%) test “peak luminance.”
📐 Presets (1%, 5%, 10%, 25%, 50%, FULL): These are the standard industry calibration sizes used for monitor reviews and HDR certifications.
⬅️➡️ Navigation: Click the background or use Arrow Keys to cycle through window size presets.
🔋 ABL/ASL Behavior: On OLED screens, you will notice the screen dims significantly as the white window grows larger. This is the Automatic Brightness Limiter (ABL), which prevents overheating and protects the power supply.
☀️ Peak Brightness: Most HDR displays achieve their highest nit values at the 1% or 10% window sizes. Watch for any flickering or instability in the backlight as you change sizes.
✨ Haloing (LCD/Mini-LED): On displays with zone dimming, look for a “glow” around the white box against the absolute black background.
A high-quality HDR display should maintain consistent window brightness up to at least 10% and have a smooth, predictable dimming curve as APL increases. If your screen has “aggressive ABL,” the brightness will drop sharply the moment you move past a 10% window, which can be distracting during productivity work or gaming.
Online monitor brightness tester, HDR peak luminance tool, APL behavior check, OLED ABL diagnostic, nit measurement helper.
The Stuck Pixel Fixer is a dedicated maintenance utility designed to attempt repairs on “stuck” pixels by rapidly cycling sub-pixels through various color states. This high-speed stimulation can sometimes “unstick” the liquid crystals that have become trapped in a specific state.
This tool generates rapid, high-contrast flashing patterns. 🚫 DO NOT look directly at the screen while the fixer is running.
🧣 Cover the active area with a cloth or look away from the monitor.
🛑 Stop immediately if you feel any discomfort.
🔴🟢🔵 Solid Flash vs. Static RGB: “Solid Flash” cycles the entire area through primary colors, while “Static RGB” creates a high-frequency noise pattern. Both are effective; some pixels respond better to one than the other.
🎯 Spot Fix vs. Fullscreen: Use “Spot Fix” to drag a localized box over a specific defect. Use “Fullscreen” if you have multiple issues or want to “refresh” the entire panel.
⏱️ Timer: Set a duration from 1 minute to 60 minutes. Deeply stuck pixels often require at least 30 minutes of continuous stimulation.
📏 Size: Adjust the box size when in “Spot Fix” mode to perfectly cover the affected area.
🟥 Stuck Pixel (Colored): A pixel that is permanently Red, Green, or Blue. These have the highest chance of recovery (approx. 50-60%) using this tool.
⬛ Dead Pixel (Black): A pixel that remains black on a white background. This is usually a physical hardware failure (burned-out transistor) and is rarely fixable by software.
⬜ Hot Pixel (White): A pixel that is permanently white. These are often difficult to fix but can sometimes be improved by the “Static RGB” mode.
If the pixel is still stuck after 60 minutes, it may be a permanent hardware defect. You can try a second pass after the monitor has “rested” and cooled down. For new monitors, check your manufacturer’s “dead pixel policy” for replacement options.
This free online stuck pixel fixer works on OLED, LCD, and LED displays, including iPhone, Android, and Desktop monitors. No download required.
The Text Sharpness test is a comprehensive suite for evaluating how your display handles typography across different sizes, weights, and contrasts. This is vital for productivity, as poor text rendering leads to eye strain during long working sessions.
🔠 Size Scaling: Displays text from 10px to 48px. This reveals the “legibility threshold” of your screen.
🅰️ Weight Rendering: Tests font weights from 100 (Thin) to 900 (Black). Look for “bleeding” where thick letters blend together, or “fading” where thin letters disappear.
✏️ Sans vs. Serif: Compares font styles to check how your monitor’s pixel grid handles the fine “hooks” (serifs) of traditional fonts.
◼️◻️ Contrast Inversion: A high-contrast block specifically designed to find sharpening artifacts.
🌓 Background (Dark/Light): Switch the entire page between “Dark” (White text on Black) and “Light” (Black text on White) modes using the buttons in the control panel. Some monitors handle one significantly better than the other.
💡 Sharpening Halos: In the “Contrast Inversion” box, look closely at the edges of the letters. If you see a bright white halo around black text, your monitor’s internal Sharpness setting is too high.
🌈 Subpixel Fringing: Look for faint rainbows (Red/Blue fringes) on the edges of vertical strokes. This can indicate a BGR subpixel layout (common in some TVs) or aggressive ClearType/CoreText settings.
🔅 Muddiness: If the smaller text (10px - 12px) looks blurry or illegible, ensure you are running at the monitor’s Native Resolution.
For the best text experience, adjust your monitor’s Sharpness setting until the white halos disappear but the text doesn’t look “fuzzy.” If you are on Windows, you should also run the “ClearType Text Tuner” to match the OS rendering to your specific panel’s subpixel layout.
ClearType test online, font rendering diagnostic, monitor sharpness checker, BGR vs RGB text test, eye strain reduction.
The Screen Uniformity test is the most fundamental diagnostic for any display. It allows you to inspect every square millimeter of your screen for physical defects, panel inconsistencies, and backlight issues.
🎨 Color Cycling: Use the hue slider or click the background to cycle through pure White, Red, Green, Blue, and Black.
⬅️➡️ Navigation: Use the Arrow Keys to quickly jump between primary color presets.
📌 Status Bar: Displays your current color and progress through the test sequence in the control panel.
💡 Backlight Bleeding: Common in IPS and TN panels. If it’s visible in a brightly lit room, it’s considered a defect.
✨ IPS Glow: Unlike bleed, “glow” changes as you move your head. This is a property of the panel technology, not a defect.
☁️ Clouding: Large, uneven “clouds” of light on a black screen signify poor internal pressure or assembly.
📋 Pixel Warranty: Most manufacturers have a specific policy (e.g., “ISO 9241-307 Class 1”) for how many dead pixels are allowed before they will replace the monitor.
Best online dead pixel test for 4K monitors, TV backlight bleed checker, and screen uniformity diagnostic. No ads or distractions.
The Refresh Rate test uses your browser’s requestAnimationFrame API to measure the real-time frequency at which your display is being updated. This is critical for ensuring that your Windows/macOS display settings, GPU drivers, and browser settings are all correctly harmonized.
🔢 Current Hz/FPS: The large number represents the average frames per second over the last 500ms.
⏱️ High-Precision Sync: We use the performance.now() timestamp to ensure 0.001ms precision in our calculations.
✅ Stable Number: If your monitor is 144Hz, the number should hover extremely close to 143.9xx - 144.0xx.
⚠️ Lower than Expected: If you have a 120Hz monitor but the test shows 60.000, your operating system or browser is likely capped. Check your display settings or ensure “Use hardware acceleration when available” is enabled in your browser.
📈 Fluctuating Number (Jitter): If the number jumps wildly (e.g., 144 to 120 to 150), it indicates that your CPU/GPU is under heavy load, or a background process is interfering with the browser’s timing.
🔋 Power Saving: Laptops on battery often cap the refresh rate to 60Hz. Plug in or set to “High Performance” to unlock the full rate.
🖥️ Multi-Monitor setups: Many browsers sync to the refresh rate of the “slowest” monitor in a multi-monitor setup if windows are overlapping.
🔗 VSync: If you see “60” but want “144”, make sure your HDMI or DisplayPort version supports the higher bandwidth and that the cable is rated for it.
Accurate 144Hz test, 240Hz monitor check, 360Hz diagnostic, browser FPS meter, online Hz tester.
The Chroma Subsampling test verifies that your computer and display are communicating with full color resolution. This is critical for reading text, coding, and seeing fine UI details without distracting “color fringing.”
This test uses high-contrast color-on-color text to stress the display interface: 🟦🟥 Cyan/Red Block: Displays Red text on a Cyan background.
🟪🟦 Magenta/Blue Block: Displays Blue text on a Magenta background.
🔳 Pattern Grid: Includes 1-pixel alternating lines of primary colors.
🔎 Text Clarity: Look closely at the “Quick Brown Fox” text. Is it perfectly sharp?
If you “fail” this test, your display is discarding 50% to 75% of the color information to save bandwidth.
Free online 4:4:4 chroma test. Troubleshoot blurry text on TVs-as-monitors and optimize HDMI signal quality for professional work.
The Gray Uniformity test is a deep-dive diagnostic for panel illumination and manufacturing consistency. While the primary Screen Uniformity test uses pure colors, this test uses “mid-tones” where panel defects are often much more visible to the human eye.
🩶 Grayscale Presets (5%, 10%, 20%, 50%, 80%): Cycle through different brightness levels using the buttons in the control panel. The 5% Gray screen is particularly famous for identifying issues on OLED panels, while 50% Gray is best for LCDs.
⬅️➡️ Navigation: Click the background to advance, or use the Left/Right Arrow Keys to jump to specific luminance levels.
📌 Status Indicators: See exactly which percentage of peak luminance you are viewing in the control panel.
No panel is perfectly uniform. However, on a high-quality monitor, you should not be able to see any of these artifacts in normal daily use. If DSE or banding is visible while watching a movie or playing a game, it may be grounds for a warranty claim (Panel Lottery).
Online DSE test, OLED vertical banding checker, vignetting diagnostic, monitor uniformity lottery helper.
The Pixel Inversion test is one of the most demanding diagnostics for display electronics. It exposes how a panel manages voltage polarity across its pixel grid and checks for interference between the sub-pixel structure and the refresh signal.
🔳 Pattern (Checker, Horizontal, Vertical): Different panels use different “Inversion schemes” (column, row, or dot inversion). Cycle through these using the buttons in the control panel to find which one triggers a reaction from your monitor.
📏 Size (1px, 2px, 4px): Tests the spatial frequency of the inversion. Native 1:1 pixel mapping (1px) is the standard test for most high-end monitors.
🏎️ Speed (Pixels/Frame): Adjust the motion speed using the slider from -10 to +10. Setting speed to Static (0) checks for purely spatial artifacts, while Motion (+1 to +5) is best for finding voltage-related flicker.
↔️ Direction: Negative speeds move the pattern to the left, positive to the right.
⚡ Pixel Walk (Inversion): While looking at the gray pattern, does the screen appear to “flicker” or “shimmer”? Do you see a mesh-like pattern that seems to “walk” across the screen? This indicates the panel’s inversion scheme is struggling to balance voltage correctly.
📡 Crosstalk: Look for horizontal or vertical shadows/lines that extend from the moving pattern across the rest of the screen.
🎨 Asymmetric Response: If the gray pattern takes on a distinct color tint (like green or purple) only when moving, it reveals that the pixels turn on faster than they turn off (or vice versa).
Almost all LCDs show some level of pixel walk on at least one pattern, especially at high refresh rates. However, it should not be visible in normal content. If you see heavy flickering at 144Hz but not at 60Hz, it suggests the T-CON (Timing Controller) is pushed to its stability limit.
This tool helps troubleshoot “Scan Line” issues on Samsung Odyssey monitors, “Pixel Walk” on high-refresh gaming panels, and general VGA/Signal clock interference.
The Contrast test evaluates your display’s “Dynamic Range”—its ability to show distinct levels of brightness simultaneously. Proper contrast is essential for seeing detail in both dark shadows and bright highlights, providing depth and realism to images.
🎨 Color Channels (Gray, Red, Green, Blue, Cyan, Magenta, Yellow): Use the colored buttons in the control panel to switch between different color channels.
📏 Gamma Target Strips: Vertical blocks represent gamma values from 1.8 to 2.6.
⬅️➡️ Navigation: Click the background or use the Left/Right Arrow Keys to change color channels.
📌 Status Bar: The active channel name is displayed in the control panel for easy reference.
⬛ Black Crush: Look at the first 3 or 4 bands near the black side. If they look like a single solid black block, your monitor is “crushing” shadows, and you are losing detail in dark scenes.
⬜ Highlight Clipping: Look at the last 3 or 4 bands near the white side. If they blend together, your Contrast setting is too high, and you are “clipping” bright details.
⚖️ Neutrality: On the Gray channel, look for any unwanted colors. The bands should look like “pure” gray. If some look slightly green or blue, your monitor’s color balance is uneven.
Set your monitor to “Standard” or “sRGB” mode. Avoid “Dynamic Contrast” which often hides these bands by constantly changing the backlight. If you see clipping at the white end, try lowering your monitor’s physical Contrast setting until you can see the boundary between the last two bands.
Comprehensive online contrast ratio test, dynamic range checker, black crush diagnostic, and highlight clipping tool for HDR and SDR monitors.
The Aliasing test (also known as the Jaggies test) reveals how your monitor renders fine, angled lines. It is an essential diagnostic for gamers and digital artists to understand the inherent sharpness and scaling quality of their panel’s pixel grid.
🧷 Antialiasing Toggle (ON/OFF): Switch between raw “crisp edges” (1:1 pixel rendering) and smoothed, interpolated rendering.
🏎️ Rotation Speed (1–50°/s): Adjust how fast the line oscillates to check for motion artifacts during rotation.
📐 Angle Range (±1–90°): Set the arc of the oscillation. Small angles are best for finding subtle “stair-stepping.”
📏 Line Width (1–20px): Test how different line weights interact with the pixel grid.
🎨 Custom Colors: Use the color pickers to test aliasing under different contrast conditions (e.g., Red on Green).
〽️ Stair-Stepping (Jaggies): With Antialiasing OFF, look for jagged steps in the line. High-resolution 4K screens will show much smoother steps than 1080p screens.
🌊 Moire Patterns: At specific angles, you might see shimmering “ripples” along the line. This indicates a mismatch between the content resolution and the panel’s native pixel layout.
✨ Sharpening Artifacts: If you see bright “halos” or white shadows around the line, your monitor’s internal sharpening is set too high.
A high-quality monitor should render 1px lines with consistent thickness at all angles. If the line appears to “chunk” or get thicker at 45 degrees, your display might be performing internal scaling. Gaming at native resolution is the best way to minimize aliasing. If you see extreme jaggies, consider enabling software-level AA (like FXAA, TAA, or DLSS) in your games.
Online jaggies test, diagonal line aliasing tool, pixel mapping diagnostic, monitor sharpness evaluator. Works for OLED and LCD gaming monitors.
The Gamma test is an essential precision tool for verifying your display’s “Luminance Curve.” This determines how your screen translates numerical signal color (input) into actual light (output). Incorrect gamma can make an image look “washed out” or “too dark” even if brightness and contrast are theoretically correct.
🏁 The Checkerboard Background: We use a pixel-perfect checkerboard pattern of alternating black and white pixels. This represents a perfect 50% luminance average.
📏 The Solid Strips: These vertical strips display solid colors calculated for specific gamma targets: 1.8, 2.0, 2.1, 2.2, 2.3, 2.4, 2.6.
🎨 Channels (Gray, Red, Green, Blue): Use the buttons in the control panel to switch between color channels. This helps you identify if one specific color sub-pixel has a “gamma shift.”
⬅️➡️ Navigation: Click the background or use the Left/Right Arrow Keys to change color channels.
🌤️ Gamma < 2.2 (e.g., 1.8): Your screen is displaying mid-tones too brightly. Images will look flat and “washed out.” Common on older Macs or monitors in “Office” modes.
🌑 Gamma > 2.2 (e.g., 2.4): Your mid-tones are too dark. This is often preferred for dark-room movie watching but can lead to “shadow crushing” in gaming.
Online gamma calibration tool, gamma 2.2 test, sRGB monitor setup, display luminance curve diagnostic.
The Response Time test is a pursuit-camera style simulation that helps you visualize Gray-to-Gray (GtG) performance. It reveals how quickly your display’s pixels can transition between different colors and brightness levels.
🏎️ Pixel Speed (PPS): Adjust the speed using the slider from 100 to 3000 Pixels Per Second. Higher speeds make ghosting and smearing much more obvious.
📏 Width & Gap: Adjust the size of the moving bars to test how different surface areas affect your perception of motion.
🎨 Custom Colors: This is the most powerful part of the tool. • Obj L / Obj R: Change the colors of the moving bars. • Bg: Change the background color. 💡 Tip: Set Bg to Dark Gray and Obj to Light Gray to test “Dark Level Transitions”.
👻 Ghosting (Motion Blur): Do you see a faint, blurry “trail” left behind the bars? This indicates the pixels aren’t turning off fast enough.
✨ Inverse Ghosting (Overshoot): Do you see a bright or white “glow” trailing or leading the bars? This means your monitor’s Overdrive (Response Time) setting is too high, causing the pixels to “overshoot” their target color.
🖤 Black Smearing: Set the Background to Black and the Objects to a dark color. If you see a long, muddy trail, your panel (likely VA) has slow dark-level transitions.
For a clean gaming experience, you want the bars to look as sharp as possible with no visible trails.
Monitor ghosting test, UFO test alternative, motion blur diagnostic, VA panel smearing check, IPS response time tool.
The Viewing Angle test evaluates how consistently a display renders color and brightness when viewed from different positions. This is a critical metric for large monitors, televisions, and professional design work where color accuracy must be maintained across the entire surface.
🎨 Color Shift: When viewed from the side, does the “White” background take on a blue or yellow tint? Do the primary colors lose their vibrancy?
🌫️ Gamma Shift (Contrast Loss): Does the image appear “washed out” or desaturated as you move off-center? This is very common in VA panels.
✨ Black Level Glow: On an IPS panel, the corners may appear to “glow” with a silver or gray haze when viewed at an angle. This is IPS Glow.
🔄 Inversion: On older TN panels, viewing from below often causes the colors to completely invert (e.g., black becomes white).
💎 OLED/AMOLED: Best-in-class viewing angles. Colors remain nearly identical up to extreme angles.
🖥️ IPS/AAS/PLS: Very good performance with minimal color shift, but prone to IPS Glow in the corners.
📺 VA/MVA: Significant gamma shift. The “Black” level often rises, and colors become pastel-like at angles.
⚠️ TN: Poor performance. Drastic shifts occur even with minor head movements.
Compare IPS vs VA viewing angles online. Professional color shift diagnostic for ultrawide monitors and designer displays.
The Black Level test determines how well your monitor can distinguish between absolute black and “near-black” shades. This is essential for seeing detail in dark video games, noir movies, and professional color grading work.
🔲 The Grid: We display 16 near-black squares focused on the most useful shadow-detail range: RGB 1-8, then 10, 12, 14, 16, 18, 20, 24, and 28.
⬛ The Background: The background is set to absolute black (RGB 0, 0, 0).
🏷️ Labels: Tiny labels indicate the RGB color value of each box.
🖤 OLED Displays: These should easily show Box 1 against the background because they have infinite contrast. If they don’t, check your “Black Level” or “Luminance” settings.
🖥️ IPS/LCD Displays: These often have a “Minimum Luminance” (IPS Glow). Box 1 might be hard to see because the background itself is slightly gray.
🔧 Troubleshooting: If you see a heavy “gray haze” instead of deep black, ensure your PC is outputting a “Full Dynamic Range” (0-255) signal in your GPU settings, not “Limited” (16-235).
Free online black level calibration, fix crushed blacks, monitor shadow detail test, display brightness setup tool.
The White Saturation test evaluates how well your monitor handles bright highlight detail. If your display is poorly calibrated or has the contrast set too high, subtle details in clouds, snow, or bright skin tones will “clip” and appear as flat white blobs.
⬜ The White Grid: We display 16 near-white squares centered on the highlight-clipping range: RGB 235, 238, 240, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, and 254.
🔳 The Background: The background is set to absolute white (RGB 255, 255, 255).
🏷️ Labels: Tiny labels indicate the RGB value of each box.
🔧 How to Fix Clipping: Go to your monitor’s physical menu (OSD) and lower the Contrast setting until you can see the boundary between Box 254 and the white background.
☀️ HDR Displays: On HDR-capable monitors, ensure you are testing in the correct mode. Some HDR implementations “hard clip” everything above a certain luminance to maximize brightness, which may lead to poor results in this specific sRGB test.
Free online highlight clipping test, monitor contrast calibration tool, white saturation checker, and sRGB dynamic range diagnostic.
The Gradient Banding test checks for ‘Posterization’—a visual artifact where smooth color transitions are broken up into distinct, ugly steps. This is a key test for photographers, designers, and HDR enthusiasts who require deep color accuracy.
🌫️ Linear Grayscale Gradient: The standard test for overall bit-depth and luminance transition from pure black to white.
🔴🟢🔵 Primary Channels (Red, Green, Blue): Check if specific color subpixels have trouble with smooth power curves or “voltage steps”.
🟦🟪🟨 Secondary Channels (Cyan, Magenta, Yellow): Verify the display’s internal processing for combined colors.
⬅️➡️ Navigation: Click the background or use Arrow Keys to cycle through the available channels.
📉 Step Patterns (Banding): Do you see clear vertical lines or “steps” instead of a silky-smooth transition? This indicates the panel is struggling to represent 8-bit or 10-bit color depth accurately.
✨ Dithering Noise: Look closely at the gradient. Do you see a faint “sand-like” moving pattern? This is Temporal Dithering (FRC), a technique used by panels to simulate more colors than they can natively show.
🎯 Gray Tracking: In the Grayscale gradient, look for unintended tinting. If certain sections look slightly green or pink, your monitor’s gray tracking is inconsistent across the brightness range.
While almost all digital gradients have some banding due to 8-bit signal limitations, a high-quality 10-bit panel should look nearly perfect from a normal viewing distance.
Professional online gradient test for 8-bit vs 10-bit displays. Detect posterization, dithering, and color depth issues without expensive hardware.
The Blooming test is a high-stress diagnostic for displays using Local Dimming technology, such as Mini-LED and Full Array Local Dimming (FALD) LCDs. It reveals how well the display can maintain deep blacks while showing bright, moving objects.
🏎️ Speed (0–20): Adjust how fast the white ring moves. Motion is critical because it tests the response time of the dimming zones.
📏 Thickness (1–50px): Change the width of the ring. Thinner lines are much harder for local dimming algorithms to illuminate accurately without “bleeding” into adjacent black zones.
⭕ Diameter (10–800px): Larger objects may bridge multiple dimming zones, helping you identify the physical size and shape of your panel’s dimming grid.
✴️ Haloing (Blooming): Look for a gray, blue, or white “cloud” of light surrounding the moving white ring. This is Blooming: light from the backlight zones leaking into pixels that should be pure black.
🐢 Zone Lag: Does a “shadow” of light follow the ring? This indicates your monitor’s local dimming controller is slow to update, causing trailing artifacts in dark scenes.
⚡ Dimming Artifacts: Watch for flickering as the ring passes between zones. Some displays may “pulsate” or change in brightness as the object moves.
While OLED displays have per-pixel lighting and should show zero blooming, all LED-backlit screens will have some degree of haloing.
Professional Mini-LED blooming test. Evaluate FALD haloing, OLED near-black performance, and local dimming zone response time online.
How to use Screenfix
Select any test from the dashboard to begin. Each test is designed to evaluate a specific aspect of your display's performance — from color accuracy to pixel defects.
For best results, run each test in fullscreen mode (press F11 on desktop or use your browser's fullscreen option). This eliminates browser UI interference.
Touch Devices: Tap the left or right edges of the screen to navigate between tests. Swipe horizontally to change slides within a test.
Desktop: Use the ← → Arrow keys to navigate between tests. Click screen edges as an alternative. Press ESC to return to the dashboard.
Controls: Many tests have adjustable settings (sliders, presets, color pickers) in the bottom control panel. Use these to fine-tune each test for your specific display.
The UI (header, controls) will auto-hide after 5 seconds of inactivity to give you an unobstructed view of the test pattern. Move your mouse or tap the screen to bring controls back.
Tap the info icon on any test card to read a detailed description of what the test measures and what to look for.
No display is perfect. Minor backlight bleed, slight color shifts at extreme angles, and imperceptible banding are all normal — especially on consumer-grade monitors.
Dead or stuck pixels appear as dots that remain a fixed color regardless of the test pattern. Use the Stuck Pixel Fixer tool to attempt recovery before contacting your manufacturer.
Compare with specs. Use the Gamma test to verify your display targets γ2.2, and the Refresh Rate test to confirm your monitor runs at its advertised Hz.
Legal & Disclaimer
This application contains patterns involving high-flicker and high-contrast strobing. These may trigger seizures for individuals with photosensitive epilepsy.
Screenfix.app is provided "as is". We are not responsible for any hardware damage, image retention, or burn-in that may result from extended use.
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