A dead pixel test cycles a display through a small set of exact, single-color fields so the eye can spot points that do not match the surrounding background. Most browser-based tests, including the eight-color Dead Pixel Test, fill a fullscreen panel with documented sRGB values like #000000 for black and #ffffff for white, then let the viewer move between them with a click, the Space key, or the arrow keys. Because each color field isolates a different combination of red, green, and blue channels, a pixel that is stuck dark will reveal itself on white and on the primaries, while a pixel that is stuck bright will stand out on black and on every saturated field. This is a visual aid, not a hardware diagnostic: the test identifies the requested stimulus and lets you record what your eyes see, but it does not measure the panel, scan the hardware, or upload anything. The goal is to separate what looks wrong on screen into a clear, repeatable observation you can hand to a manufacturer.
The Eight Solid Colors and Their Purpose
The eight-color dead pixel test is built from a small, deliberate fixture of CSS named colors that exhaustively probe the three sRGB channels. Every value is a documented CSS Color 4 named-color entry, not an approximate theme color, which is what makes the method reproducible across browsers and machines.
| Pattern | Hex value | Channels lit | What it stresses |
|---|---|---|---|
| Black | #000000 | None | Always-on defects and bright stuck points |
| White | #ffffff | Red, green, blue | Always-off defects and dark stuck points |
| Red | #ff0000 | Red only | Green and blue subpixel defects |
| Lime | #00ff00 | Green only | Red and blue subpixel defects |
| Blue | #0000ff | Blue only | Red and green subpixel defects |
| Cyan | #00ffff | Green and blue | Red subpixel defects |
| Magenta | #ff00ff | Red and blue | Green subpixel defects |
| Yellow | #ffff00 | Red and green | Blue subpixel defects |
The color labeled "green" in the cycle is actually the CSS named color lime at #00ff00, which lights only the green channel at full intensity. CSS also defines a darker named green at #008000, but the test deliberately uses the single-channel maximum so the green subpixel is fully exercised the same way red and blue are. By moving through all eight values, the test independently stresses each subpixel in four ways: alone (the three primaries), in pairs (cyan, magenta, yellow), all together (white), and not at all (black). A defect that lives in one subpixel will surface on the fields where that channel is supposed to be active and disappear where it is supposed to be off.
How the Visual Field Inspection Works
A dead pixel test works because each solid color field is, by construction, exactly one color across the entire panel. If a point on the panel does not match the surrounding background, it is either a real physical defect or something sitting on top of the display, and the eye is unusually good at detecting that single mismatched point once the rest of the screen is uniform. The mechanism is simple: the browser paints a single CSS background color onto a focusable panel that covers most of the viewport, with no images, text gradients, or anti-aliased edges that could distract the viewer. A progress line at the edge of the panel reports the current pattern name, its position in the sequence, and the exact hexadecimal sRGB value being shown, so the viewer can verify what they are actually looking at.
The viewer moves through the sequence by clicking the panel, pressing Space, or using the arrow keys. Forward and backward wraparound is supported, which means you can loop the sequence or step backward to compare a suspect point against the color you just left without losing your place. Fullscreen is requested only when the user activates the Start button, because the browser's fullscreen API requires a direct user gesture; if the request is denied because of permissions, embedding, platform policy, or user settings, the in-page panel still works and the test continues as normal.
Run a Dead Pixel Test Step by Step
The following procedure is the verified operating flow for the eight-color Dead Pixel Test and produces a usable observation you can hand to a manufacturer.
- Clean only the outer display surface using the manufacturer's safe method, then select Start fullscreen test.
- Inspect each of the eight colors in order: black, white, red, lime, blue, cyan, magenta, and yellow. Click the panel, press Space, or use the arrow keys to advance or step backward.
- Look at the center first, then sweep toward the edges and corners, since defects near the bezel are easy to miss on a single field.
- Note any stationary point that stays the wrong color on more than one field, because a single-field artifact is usually dust, reflection, or a rendering glitch rather than a panel defect.
- Step backward to compare a suspect point against an adjacent color if you are unsure whether it is really stuck, and watch whether it tracks the channel you are lighting.
- Exit fullscreen normally with Escape or the browser's normal controls when you are done, then consult the manufacturer's diagnostics before any repair decision.
If fullscreen is denied for any reason, continue in the in-page panel; the eight colors still cycle and the rest of the procedure is unchanged.
Interpreting Each Color Field: What Stands Out
Different solid fields make different visual mismatches easier to notice, which is why the test walks through all eight rather than stopping at black and white. A point that remains dark on white or on a primary field is not emitting light when its subpixel is asked to, the classic always-off defect that is most visible against bright backgrounds. A point that remains bright on black is not turning off when its subpixel is asked to, the always-on defect that shows up as a single bright dot in a dark field. A point that shows an unexpected color component, such as a green tint on red or a red tint on blue, suggests a stuck subpixel on a channel that should be off. An artifact that changes shape or position when you resize the window, switch colors, or reload the page is almost certainly outside the panel: dust, a smudge, a screen-protector bubble, or a browser rendering quirk.
A point that remains mismatched across several fields, especially across the primaries and white, is a much stronger candidate for a real panel issue than one that appears on a single color. A bright dot on black alone is suspicious, but a bright dot on black, on red, on blue, and on cyan is far more likely to be hardware.
Factors That Change What You See on Screen
The CSS color the test requests and the physical light the display emits are not guaranteed to be identical, and the test itself is explicit about this. Browser color management, the operating system's color profile, HDR mode, panel gamut, subpixel layout, scaling, viewing angle, local dimming, image enhancement, burn-in protection, and hardware calibration can all shift what your eyes see on each color field. The W3C specification defines the CSS color values; it does not certify the physical output of a particular monitor, so the panel identifies the requested stimulus rather than measuring the emitted color.
The same caution explains why a screenshot is not a substitute for looking at the panel. A physical defect generally does not appear in a screenshot, while a rendering artifact might, so a captured image can sometimes help you tell the two apart when interpreted carefully. For a deeper treatment of how each of these factors shifts the result, see Dead Pixel Test Accuracy: What Affects the Visual Check.
After the Visual Check: Manufacturer Diagnostics
Whatever the test shows, manufacturer diagnostics and warranty policy remain the appropriate authority for repair or replacement decisions. The eight-color method is a visual aid that produces a documented observation; it does not measure the panel, certify the hardware, or predict the outcome of any service action. If you see spreading damage, electrical symptoms, or impact damage, stop using the display and follow qualified manufacturer guidance.
Do not apply pressure, tap the panel, heat it, rapidly flash the test, or follow a destructive "pixel-fixing" claim because of what this visual check shows. The test deliberately uses static fields and provides no rapid strobe or seizure-risk animation, and any tool that promises to repair a pixel through a browser sequence should be treated as untrusted. The reliable contract is narrow: render eight documented CSS sRGB color values in a large focusable panel, support wraparound navigation, request fullscreen only after direct user action, and clearly separate a visual aid from hardware diagnosis or remediation.
Finally, no screenshot, display identifier, color profile, observation, or navigation history leaves the browser. The current pattern index lives only in the open tab and resets on reload, so the visual check is private by construction; the result you take to the manufacturer is the one written down by hand from what your eyes actually saw on each of the eight fields.