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Free Online Screen Test — Backlight Bleed & Uniformity

Uniformity, backlight bleed, color banding, and sharpness checks.

Switch between test modes to evaluate different aspects of your display.

Solid Colors

How it works

How to use the screen test suite

Each mode in this tool targets a specific aspect of display quality. Switch between them in order and inspect the pattern carefully. For the most accurate results, set your monitor to its native resolution, disable any dynamic contrast or HDR modes, and work in a dimly lit room.

Solid Colors

Full-screen red, green, blue, white, and black checks for dead pixels, stuck sub-pixels, and overall color uniformity. A uniform patch of color across the entire screen — no bright or dark spots — is the goal.

Gradient Banding

Smooth gradients from black to white and through primary colors test the display color depth. Visible steps or stripes indicate a 6-bit panel with FRC dithering. True 8-bit panels produce nearly invisible transitions. 10-bit panels appear perfectly smooth. Banding is most noticeable on large uniform gradient areas.

Grid / Convergence

A fine grid of thin lines checks geometry, pixel mapping, and moiré patterns. Lines should be straight, evenly spaced, and the same thickness across the entire screen. Wavy or bent lines suggest a display scaling issue or panel defect.

Sharpness Text

Small text rendered at the corners and center of the screen tests focus and resolution accuracy. If text looks blurry, smeared, or has color fringing, the display may not be at its native resolution or sharpness settings may be too high.

Backlight Bleed

Pure black fullscreen mode reveals light leaking from the edges of the panel. Some IPS glow in the corners is normal, but large glowing clouds or bright hotspots indicate excessive backlight bleed. This is most visible at high brightness in a dark room.

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Frequently Asked Questions

What is backlight bleed and how do I check for it? expand_more
Backlight bleed is cloud-like patches of lighter gray that appear around the edges or corners of an LCD screen when the screen is black. To check for it, go to a dark room, set brightness to 100%, and switch to the pure Black mode. If you see uneven bright patches especially near bezels, that is backlight bleed. Some bleed is normal on IPS panels, but excessive bleeding warrants a return or replacement.
What does color banding tell me about my display? expand_more
Color banding shows up as visible stripes instead of a smooth gradient. It indicates the display has limited color depth — typically 6-bit + FRC instead of true 8-bit or 10-bit. A display that shows smooth, band-free gradients has higher color accuracy and is better for photo and video work.
What is the convergence grid used for? expand_more
The fine grid pattern checks for geometry issues, moiré artifacts, and pixel alignment. If grid lines appear wavy, bent, or unevenly spaced, the display may have scaling problems, timing issues, or a failing TFT matrix. It is especially useful for testing CRT-to-LCD adapters and vintage monitors.
Why is the sharpness text test important? expand_more
Fine text in the corners and center reveals if your display is running at its native resolution. Blurry or smeared text indicates non-native scaling, incorrect ClearType settings, or a dirty screen. Sharp, crisp text across the full screen confirms proper resolution and good display focus.
How does the gradient test differ from the solid color test? expand_more
Solid colors reveal dead or stuck pixels, while gradients reveal the display color depth and dithering quality. A good panel shows a perfectly smooth transition from one shade to the next. Budget panels show visible steps or lines in the gradient. Both tests together give a complete picture of display quality.