Monitor Test
Comprehensive display diagnostics — dead pixels, color, contrast, refresh rate, uniformity and more
Your Display at a Glance
Dead Pixel Test
Enter fullscreen and look for pixels that do not match the solid background color. Click or press arrow keys to cycle through colors.
Pixel Fix Mode (Flash)
⚠ Warning: Rapid flashing may trigger discomfort in people with photosensitive epilepsy. Proceed with caution.
Rapidly cycles RGB colors at ~60fps. May help unstick stuck sub-pixels.
Color & Gradient Test
Evaluate color accuracy, gradient smoothness, and wide color gamut coverage.
P3 gamut pattern: the outer ring uses colors beyond sRGB. On a P3-capable display you will see a clear color boundary. On an sRGB display, the ring looks identical to the background.
Contrast & Levels Test
Test black levels, white clipping, gamma linearity, and near-black/near-white shadow detail.
Refresh Rate Test
Measures your display's actual refresh rate using requestAnimationFrame timestamps. Results reflect what your GPU is delivering to the monitor.
Warming up — discarding first 30 frames…
High variance in frame intervals may indicate VRR (FreeSync / G-Sync) is active.
Result lower than expected? On multi-GPU systems the browser often runs on the integrated GPU, which may only drive a 60 Hz output. Fix: Windows Settings > Graphics > select your browser > High performance (dedicated GPU).
Uniformity & Backlight Test
Check for backlight bleeding, vignetting, and Mini-LED halo artifacts. Best done in a dim room with monitor brightness reduced.
Motion Blur Test
7 motion tests in one fullscreen sequence. Configure speed, background and flicker frequency below, then start.
Sharpness & Clarity Test
Evaluate pixel sharpness, sub-pixel rendering, and text readability.
Viewing Angle Test
Detect color shift, IPS glow, and contrast loss when viewing from off-center angles.
View the screen from the sides, top, and bottom while patterns are displayed and observe any color shift or brightness change.
How the Monitor Test Works
This tool uses the HTML5 Canvas API and browser screen metrics to run all diagnostics locally in your browser — no download, no plugins required. Each test tab provides specialized patterns designed to reveal specific display characteristics that are difficult to detect under normal conditions.
What Is a Dead Pixel?
A dead pixel permanently stays off (black). A stuck pixel is fixed at one color — red, green, or blue. Uniform solid-color screens make both defects easy to spot. The Pixel Fix mode rapidly flashes colors to potentially restore stuck pixels by exercising the liquid crystal cells.
Why Refresh Rate Matters
This tool timestamps every requestAnimationFrame callback using the browser high-precision performance.now() clock. After a 30-frame warm-up, the average interval across 60 consecutive frames is converted to Hz. The result is the actual frame cadence the browser delivers to your display, which can be lower than your panel spec if the browser is power-throttled, the window is not in the foreground, or the browser is rendered on a GPU different from the one driving your high-refresh display.
On multi-GPU systems (e.g. laptop with integrated + dedicated graphics) the browser often defaults to the integrated GPU. If the integrated GPU drives a 60 Hz output, the browser caps rAF at 60 Hz even if a dedicated GPU is connected to a 240 Hz display. Fix: open Windows Settings > Graphics, select your browser, and set it to High performance (dedicated GPU). NVIDIA and AMD control panels offer the same option under per-application settings.
HDR & Wide Color Gamut
HDR monitors produce significantly brighter highlights and deeper blacks than SDR displays. The Screen Info tab shows whether your browser and OS report HDR (dynamic-range: high) and wide color gamut (P3/Rec.2020) support. The Color tab's P3 Gamut Border pattern visually confirms whether your display can render colors outside the sRGB spectrum.
Frequently Asked Questions
- Does this tool work on mobile?
- Screen Info, Refresh Rate, and most static tests work on mobile. Fullscreen-based tests require a tap to enter. For the best experience, use a desktop or laptop with a dedicated monitor.
- Can rapid flashing really fix stuck pixels?
- There is anecdotal evidence that rapidly alternating pixel colors can sometimes restore stuck sub-pixels, but it is not guaranteed. The fix mode is experimental and results vary.
- Why does my measured refresh rate not match my monitor spec?
- The most common cause on multi-GPU systems is that the browser is rendered by the integrated GPU, which may only drive a 60 Hz output - even if your dedicated GPU connects to a 240 Hz monitor. Fix: open Windows Settings > Graphics, select your browser, set it to High performance (dedicated GPU). Other causes: browser power-saving mode caps rAF at 60 fps; the browser window lost focus; or heavy background GPU load.