What is Screen Color Tester?

Screen Color Tester fills your display with a solid color, a smooth gradient, or a rapid color cycle so you can spot dead, stuck, or hot pixels on your monitor. Switch between eight pure colors, run the pixel fixer to revive stuck sub-pixels, or scan a gradient for banding.

Each solid color fills the viewport with a single uniform value so any pixel that fails to reproduce it stands out. Pure red exposes green and blue sub-pixel faults, pure white reveals dust and dim cells, pure black uncovers backlight bleed and stuck-on pixels. Yellow, cyan, and magenta cover the secondary channels so mismatched sub-pixel pairs cannot hide. Pixel Fixer rapidly cycles the eight colors at sixty changes per second — a known trick to coax stuck sub-pixels back into normal operation after about half a minute. Gradient mode draws a smooth black-to-color ramp that exposes posterization and banding on panels with poor bit depth. Fullscreen mode hides every distraction so nothing stands between your eye and the panel.

How to use

1. Click a color button or press arrow keys to fill the screen with that solid color.
2. Examine your entire screen carefully for any dots that don't match the background color.
3. Cycle through all colors — dead pixels show as black dots, stuck pixels show as colored dots on non-matching backgrounds.

When to use

• Inspecting a new or refurbished monitor before the return window closes.
• Diagnosing flicker or dead spots after dropping a laptop or phone.
• Checking backlight uniformity on an OLED or IPS panel in a dark room.

Result

Testing a new 27-inch monitor — cycle through pure red, green, blue, white, and black. A stuck pixel appears as a bright green dot on the pure red screen, confirming a sub-pixel defect.

FAQ

What's the difference between a dead pixel and a stuck pixel?

A dead pixel stays black on every colour because its transistor never receives power. A stuck pixel shows one fixed sub-pixel — usually red, green, or blue — and ignores the colour the rest of the screen is displaying. Stuck pixels can sometimes be revived with rapid colour cycling; dead ones almost never.

Why do I need to test on solid colours instead of regular content?

Photographs and websites contain too much visual noise to spot a single faulty sub-pixel. A uniform red field forces every red sub-pixel to fire at maximum, so a missing or stuck one shows up as an obvious dark or wrong-coloured dot.

Will running these colours damage my OLED screen?

A short test of a few minutes is fine. Avoid leaving a static full-white image on an OLED for hours — that's how persistent image retention starts. Cycle through the colours and don't park on one for an extended session.

How many bad pixels are normal on a new display?

Most manufacturers use the ISO 9241-307 standard. Class 1 (zero defects) is rare and expensive. Class 2 allows a few stuck or dead sub-pixels on a 24-inch monitor before it qualifies for warranty replacement. Check your maker's exact policy before filing a claim.

The custom colour picker shows a hex code — what should I test?

Mid-grey (#808080) reveals colour casts and tinting that pure values hide. A warm tan (#FFE4B5) is useful for checking colour calibration against a printed sample. Pure cyan and magenta surface mismatched sub-pixel pairs.

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