What is the Pixel Grid Test?
The pixel grid test verifies native resolution rendering and panel sharpness. At native resolution, each software pixel maps exactly to one physical pixel — the image is maximally sharp. At non-native resolutions, the display must interpolate, causing visible softness or a pixel grid overlay effect.
The test also reveals sub-pixel layout (typically RGB stripe) and checks for any persistent pixel irregularities not related to dead pixels — including sub-pixel defects where only the red, green, or blue element of a pixel is faulty.
How to Use the Pixel Grid Test
Step 1 — Set your OS resolution to native. Before testing, confirm your display settings show the monitor's native resolution (e.g., 1920×1080, 2560×1440, 3840×2160). Non-native resolutions invalidate the test.
Step 2 — Launch and display the fine grid pattern. The alternating 1-pixel checkerboard pattern appears as a uniform grey at native resolution. Any visible patterns, moiré, or inconsistent brightness indicates a rendering pipeline issue.
Step 3 — Check sharpness at corners. Tap or look closely at each corner — sharpness should be consistent across the panel. Corner softness suggests panel bow or inconsistent pixel pitch at the edges.
Step 4 — Look for coloured fringing. A 1-pixel alternating black-and-white pattern should render as pure grey. Any red, green, or blue fringing indicates sub-pixel rendering anomalies or incorrect sub-pixel layout in the OS configuration.
What to Look For
| Observation | Meaning |
|---|---|
| Uniform grey on fine checkerboard | Native resolution confirmed, rendering correct |
| Visible black grid lines on checkerboard | Non-native resolution or scaling active |
| Moiré pattern (wavy interference) | Panel pixel pitch interacting with content frequency |
| Colour fringing on fine lines | Sub-pixel rendering misconfigured or sub-pixel defect |
| Corner areas visibly softer | Panel mounting stress or manufacturing tolerance |
| Isolated coloured pixels | Sub-pixel defect (partial pixel failure) |
Scaling and HiDPI
On HiDPI (Retina) displays, the OS renders at 2× or higher — 4 physical pixels per logical pixel. At 200% scaling, the pixel grid test verifies that the 2× mapping is clean and consistent. Mismatched scaling ratios produce visible artefacts.
Windows ClearType sub-pixel rendering is optimised for RGB horizontal stripe layouts. If your monitor uses a different sub-pixel arrangement (common on some IPS panels from certain manufacturers), ClearType rendering can appear coloured on fine text.
Frequently Asked Questions
What resolution should I run the test at? Always at native resolution — the physical pixel count the panel was manufactured with. Running at any other resolution introduces interpolation, which will produce false positives in the pixel grid test.
What does a sub-pixel defect look like? A sub-pixel defect shows as a tiny point that appears coloured (red, green, or blue) rather than black or white on a dead pixel test. On a pixel grid test it appears as a persistent coloured dot that does not change with the displayed pattern.
Why does the fine grid look grey instead of black and white? At native resolution the eye cannot resolve individual 1-pixel-wide alternating columns — they merge optically into a mid-grey. This is correct behaviour. If you can distinctly see individual black and white columns from normal viewing distance, you are likely running at less than 90 PPI.
Does scaling affect pixel clarity? Yes. Integer scaling (100%, 200%, 300%) preserves pixel sharpness. Fractional scaling (125%, 150%) requires interpolation and produces softness or fringing artefacts. Use integer scaling where possible for best clarity.