Screen Test — Dead Pixel, Backlight Bleed & Grayscale Online Check
Free online screen test: solid colors for dead pixels, grayscale, gradient banding, backlight bleed and text sharpness — runs in your browser, no install.
Test cards
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Free online screen test that checks a display in one page: dead pixel scans with fullscreen solid colors, grayscale uniformity, gradient banding, backlight bleed, text sharpness, touch dead zones and motion smear. Three modes cover every depth — a one-click 5-color cycle, a step-by-step inspection wizard with a verdict, and a pro console with 8 adjustable tests. Nothing to install, nothing uploaded: every test fills your screen from the browser, on desktop, tablet or phone.
Buy a new monitor, laptop or phone? Test it on day one. A dead pixel found inside the 7-day return window is a free exchange; found a month later it is a warranty argument most vendors decline.
How to test — three steps
- Dim the room. Bleed and dark pixels only show in the dark. Turn the lights off or draw the curtains, and set brightness to maximum.
- Cycle the solid colors fullscreen. On black look for glowing dots (hot pixels) and corner glow (bleed); on white look for black dots (dead pixels); on red / green / blue a wrongly-colored dot pinpoints a damaged sub-pixel.
- Finish with grayscale and gradient. Grayscale exposes uneven brightness and tint blotches; the gradient exposes banding. If all pass, the panel is healthy.
Hot pixel, dead pixel, sub-pixel defect — what is what
| Type | Most visible on | Looks like | Cause |
|---|---|---|---|
| Hot pixel | Solid black | A tiny dot that keeps glowing white or colored | Sub-pixel stuck always-on |
| Dead pixel | Solid white | A black dot that never lights | Pixel fully failed |
| Color dot (defect) | Red / green / blue | A dot of the wrong color (e.g. black on red) | One damaged sub-pixel |
| Backlight bleed | Black + dark room | Whitish glow along edges and corners | Backlight assembly tolerance — very common |
Naming varies by site ("stuck" vs "dead"), but the detection method is identical: fill the screen with a known color and look. That is exactly what this screen test tool does.
LCD vs OLED — what to check
- LCD (most laptops and monitors): backlight bleed is the signature issue — check the four corners on pure black in a dark room. Mild glow is normal and affects nearly every panel; bright patches visible in daytime use are not. "IPS glow" in the corners is a related trait that shifts as you move your head; it is panel technology, not a defect.
- OLED (flagship phones, TV, premium laptops): pixels emit their own light, so bleed does not exist — and pure black is truly black. Instead, watch for brightness unevenness on solid gray (which also reveals burn-in-prone areas), and check low-gray banding on gradients, where OLED historically struggles.
- Both: grayscale steps must be distinguishable and neutral (a color codes table helps you judge whether tones drift); text must be crisp without red/blue fringing (fringe usually means a resolution/scaling mismatch — check system scaling before blaming the panel).
Warranty and returns: how many pixels is "too many"?
There is no universal legal threshold; each vendor publishes (or quietly applies) a pixel policy:
- Most monitor brands follow an ISO 9241-style rule: up to a handful of hot/dead/sub-pixel defects (commonly 3–5 total, with sub-limits per type) counts as within spec — no replacement.
- Phone and laptop makers are usually stricter, because a dense screen makes any dot obvious; some advertise "zero dead pixel" exchange policies, others follow the same 3–5 window.
- The 7-day (or 14/30-day) no-questions return window that many online stores offer is your strongest card: it ignores vendor pixel policies entirely. Test on day one, photograph any defect with this page open as evidence, and note the position (row/column or clock position).
Re-test occasionally after purchase: sub-pixel defects and backlight issues sometimes develop after weeks of use, and a documented early screen test makes any later claim much easier.
More free utilities — browse the tools hub.
FAQ summary
Is a browser-based test as good as software? For every visual check — pixels, bleed, uniformity, banding — yes: both just fill the screen with a color. There is nothing a native app can show that a fullscreen web page cannot.
Does it work on phones? Yes — rotate to landscape, open a color card and use fullscreen. The wizard's phone scene adds a touch dead-zone drawing test.
Can a test fix a dead pixel? No tool can promise that. Gentle "pixel massage" (rapidly cycling colors over the spot for hours) occasionally revives a stuck sub-pixel; the 7-color auto cycle gives you that pattern for free — but a fully dead pixel is hardware failure, full stop.
FAQ
Is an online screen test accurate? How is it different from desktop software?
For visual-judgment checks like dead pixels, backlight bleed and grayscale uniformity, an online fullscreen tool works exactly like native software — both just fill the screen with a given color. The only difference is convenience: it runs in the browser, with nothing to download or install.
Can I test a phone screen?
Yes. The tool works in phone and tablet browsers. After opening a color card, rotate to landscape and use fullscreen to hide the browser UI so the picture fills the screen. Tap once for the next color, swipe left or right to switch; the wizard's phone scene adds a touch dead-zone drawing test.
How many dead pixels count as normal? Can I return the device?
Warranty policies differ by brand: most vendors treat up to 3–5 lit/dead pixels as within the "normal range" and decline replacement, but within the 7-day return window most stores accept a direct return or exchange. Test a new monitor, laptop or phone on day one and keep photo evidence to support your claim.
Does backlight bleed always mean a defective screen?
LCD screens almost always have slight bleed, especially in the corners — a common trait of backlit panels; a faint glow along the edges on a black screen in a dark room is normal. Only pay attention if you see clear light patches in normal daytime use, or uneven brightness on an OLED panel.