Screen Tester Tool
Monitor & Display Diagnostic Checker
14 professional display tests in your browser. Dead pixels, refresh rate, ghosting, backlight bleed, PWM flicker, uniformity, motion blur, black/white level, overdrive, and more.
Select color → Launch fullscreen → Look for dots that don't change. Dead = always black. Stuck = fixed color.
| Type | Appearance | Cause | Common Fix |
|---|---|---|---|
| Dead Pixel | Always Black | Transistor failure | Pressure/cycle fix |
| Stuck Pixel | Fixed R/G/B | Transistor stuck ON | JScreenFix method |
| Hot Pixel | Always White | Constant leakage | Often unfixable |
| Partial Dead | Dim/Off-color | Partial failure | Rare |
🏆 TEST RECORDS (click to collapse) ▾
| ESC | Exit fullscreen / close modal |
| F | Launch fullscreen for current test |
| SPACE | Start / stop active animation |
| ← / → | Cycle through test modes |
| ↑ / ↓ | Cycle colors in fullscreen |
| 1–9 | Quick-switch to test 1–9 |
| R | Reset / clear current test |
| T | Toggle dark / light theme |
| C | Toggle compact mode |
| S | Save current test result |
| G | Open settings panel |
| Tap canvas | Start / stop animation |
| Tap swatch | Set fullscreen color |
| Swipe tabs | Scroll mode tabs |
| Long press | Instant fullscreen |
| ‹ Left arrow | Scroll tabs left |
| Right arrow › | Scroll tabs right |
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Screen Test Tool — Complete 14-Test Monitor Diagnostic Guide
Our browser-based screen test suite covers every critical aspect of monitor performance without any software installation. Whether evaluating a new purchase, debugging display issues, or profiling a monitor for color-critical work, this toolset provides professional-grade insight.
Dead Pixel & Stuck Pixel Test
Cycles through 16 solid colors — black, white, all primaries, secondaries, and near-black — to reveal pixels that fail to change color. Dead pixels remain black, stuck pixels hold a fixed color, and hot pixels are always white. The auto-cycle mode tests all 16 colors automatically at your chosen interval.
Refresh Rate Meter
Uses requestAnimationFrame to precisely measure how many frames your browser renders per second, directly corresponding to your display's actual refresh rate. The test tracks average, minimum, maximum, stability percentage, and frame drops over a configurable sample window.
PWM Flicker / Strobe Test
Generates controlled strobe patterns at frequencies from 10Hz to 250Hz. If the strobe is clearly visible or causes discomfort at a certain frequency, your monitor may use PWM dimming at or near that rate. High-frequency PWM (above 1000Hz) and DC dimming are considered flicker-free technologies.
Uniformity Test
Divides the screen into a configurable grid (3×3, 4×4, or 5×5) and fills each zone with an identical solid color. Brightness variations between zones reveal backlight uniformity issues. Color tint differences between zones indicate poor panel uniformity — particularly common in lower-cost IPS monitors.
Motion Blur & UFO Test
Animates a moving object across the screen to visualize motion clarity at different speeds. The estimated blur calculation (speed × response time) gives a theoretical blur in pixels. OLED and TN panels excel here; IPS and VA panels may show trailing. Enabling overdrive can reduce but may introduce inverse ghosting.
Black Level & White Saturation
The black level test shows near-black squares (values 0–50) on a dark background. Counting visible distinct squares measures how well your monitor resolves shadow detail. The white saturation test shows near-white squares (205–255) to detect highlight clipping and measure bright detail reproduction.
Test Results Reference
| Test | Excellent | Good | Poor |
|---|---|---|---|
| Dead Pixels | Zero defects | 1–2 outside center | 3+ or any in center |
| Refresh Rate | At spec, stable ±2Hz | At spec, some variance | Below spec or unstable |
| Response/Ghosting | No visible trail | Slight trail at high speed | Heavy ghost or smear |
| Reaction Time | Below 200ms | 200–300ms | Above 350ms |
| Backlight Bleed | Invisible in dark room | Minor corner glow | Visible at normal brightness |
| Flicker (PWM) | Not visible at any freq | Barely visible below 50Hz | Visible at 60Hz+ |
| Uniformity | All zones identical | Minor corner variation | Obvious brightness bands |
| Gradient Banding | Perfectly smooth | Subtle banding in 1 channel | Obvious steps in all channels |
Frequently Asked Questions
Use the Dead Pixel Test to fill your screen with solid colors one at a time. Dead pixels appear as black dots that don't change color. Stuck pixels appear as a fixed red, green, or blue dot regardless of the screen color. Use the auto-cycle feature to automatically rotate through 16 test colors. Examine all corners, edges, and the center carefully in a dim environment.
60Hz is sufficient for office work, video, and casual use. 120–144Hz provides noticeably smoother motion and is excellent for gaming. 165–240Hz+ is for competitive gaming where every millisecond counts. The jump from 60Hz to 144Hz is very noticeable; from 144Hz to 240Hz is more subtle and mainly benefits fast-twitch game types like CS2 or Valorant.
PWM (Pulse Width Modulation) dims LCD monitors by rapidly switching the backlight on and off. At lower brightnesses, the frequency may drop. People sensitive to flicker can experience eye strain, headaches, or fatigue. If you're sensitive, look for "flicker-free" certified monitors that use DC dimming instead. The flicker test in this tool helps you identify perceivable frequencies.
Overdrive is a feature that speeds up pixel transitions to reduce ghosting. Too much overdrive causes "inverse ghosting" — a bright or dark halo that appears ahead of a moving object. The overdrive test shows both normal ghosting (trail behind object) and inverse ghosting (corona ahead of object). The ideal overdrive setting minimizes both.
The browser may cap frame rates in background tabs. Your GPU driver settings may override the monitor refresh rate. Adaptive sync (G-Sync/FreeSync) may limit the range. Close other browser tabs, ensure your display is set to its maximum refresh rate in OS display settings, and confirm your cable supports the bandwidth required (e.g., HDMI 2.1 for 4K@144Hz).
Ghosting is caused by slow pixel response time — pixels change color too slowly, leaving a visible trail behind moving objects. Motion blur is caused by sample-and-hold, where each frame is displayed for the full refresh interval. Higher refresh rates reduce motion blur. Strobing/motion blur reduction backlight (like ULMB) can dramatically reduce both, but usually requires locking to a specific refresh rate.