Current verdict
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Pixel faults marked {{ result ? result.pixel_faults : '—' }} Other findings {{ result ? result.other_findings : '—' }} Panel {{ result ? result.width + ' × ' + result.height : '—' }}
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Clear {{ marks.length }} marks and pattern views?
{{ testHelp }} Use native resolution and confirm a suspected fault on more than one pattern; mark each fault only once.
Use the class or pledge in your warranty terms. ISO and manufacturer checks require black and white inspected; Zero bright dot needs black. Each needs at least 2 seconds of viewing.
Compare with the monitor specification: browser scaling can misreport native panel pixels. Positions are approximate.
Whole pixels, 320–16384 on each side.
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Blank keeps manual stepping. Set 3–120 seconds to advance automatically; the mark picker pauses it.
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Extra patterns:
Add checks to the sequence without changing the pixel policy.
Report details stay in this tab. No storage or network; these details never enter the URL.
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No defects marked. Start the test to record a finding.
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No defects marked. Start the test to record a finding.
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No defects marked. Start the test to record a finding.

The defect map could not load.

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No defects marked. Start the test to record a finding.
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Similar tools

A bright dot and a hazy corner can both stand out on a black screen, yet they call for different checks. Solid colours make isolated pixel faults easier to spot, even grey fields reveal uneven areas, and gradients expose abrupt changes between shades. Inspecting a new or suspect monitor means checking which appearances repeat and recording where they occur.

In a conventional colour LCD, each picture element, or pixel, contains red, green and blue sub-pixels. A fault can affect the whole pixel or just one colour component. The names used by manufacturers sometimes overlap, so the visible behaviour matters more than the informal label.

Dead or dark pixel
A full pixel remains dark when it should be lit, making it conspicuous against white. If only one sub-pixel fails to light, the spot can appear dark or tinted because the other colour components still work.
Stuck pixel or sub-pixel
A picture element fails to follow the changing image. A persistent red, green or blue dot often indicates a sub-pixel stuck on. Some manufacturers also use “stuck pixel” for a white dot.
Hot or bright pixel
All three colour components remain lit, producing a white dot against black. One colour component that stays lit is a bright sub-pixel rather than a full bright pixel.
Enlarged RGB schematic showing all three sub-pixels lit in a bright pixel and only the red sub-pixel lit in a bright sub-pixel fault.
Enlarged RGB schematic. A full-pixel fault and a sub-pixel fault belong to different counting categories.

A single background cannot expose every fault. A non-working red sub-pixel can appear dark on a red field, while a red sub-pixel stuck on is easier to see against black. Comparing black, white and primary colours helps distinguish these behaviours. Smooth grey and colour gradients serve another purpose: visible steps or stripes in an intended smooth transition are called banding.

Broad patches need a different interpretation. Backlight bleed is light leakage in an LCD, often near an edge or corner. In-plane switching, or IPS, displays can also show a glow that changes with viewing angle and distance. Moving back or looking more directly at the display can change that glow; a persistent patch in the same place deserves a separate check. Grey and white fields also reveal uniformity problems, where brightness or tint varies across an otherwise even image.

Room lighting, display brightness and viewing position affect how conspicuous these appearances become. A dim room helps reveal dark-area differences, but a faint corner visible only under extreme viewing conditions does not establish a fault. Comparison at the normal viewing position and under the manufacturer's inspection conditions makes the observation more useful.

Pixel policies set permitted counts by fault type and sometimes resolution. An ISO 9241-307 class named in a specification and a zero-bright-dot pledge describe different acceptance conditions; neither phrase alone establishes every warranty term. Model, region and coverage period matter. A seller's return terms may also differ from the manufacturer's warranty, so early inspection and dated observations help preserve the opportunity to raise a concern before an applicable return deadline.

Browser pattern tests rely on the viewer's eyes and the computer-to-display settings. They can support a repeatable visual inspection, but they do not measure calibrated brightness or colour accuracy and cannot independently identify a damaged physical pixel.

How to Use This Tool:

Open the browser window on the monitor you intend to inspect. The initial setup uses Full check, ISO Class I and a browser estimate of the screen resolution; confirm the resolution and policy before relying on the comparison.

  1. Prepare the display with a gentle clean according to its care instructions, then let it warm up. Dust can resemble a defective dot. Start from your normal viewing position and brightness. Use full brightness only if the maker's inspection procedure calls for it. For dark patterns, dim the room to reveal faint differences, then recheck suspected bleed or glow under normal lighting. Do not press or rub a suspected pixel.
  2. Choose Test type. Full check combines solid colours, dark and mid greys, and gradients. Use a focused sequence for a particular concern. If you want automatic advancement, set Pattern dwell in Advanced to 3 to 120 seconds; leave it blank for manual stepping. Optional extra patterns extend the sequence without changing the policy.
  3. Set Panel resolution to the display's native pixel dimensions, checking its specification rather than assuming This screen is exact. Choose a listed size or Custom.
    If Start is disabled after entering custom dimensions, use whole numbers from 320 to 16,384 for both width and height. Correct the displayed setup warning before starting.
  4. Select Pixel policy from the actual warranty terms. The default class is not a statement about your monitor. For Manufacturer limits, enter the applicable whole-count limits for this display. A blank field leaves that category unchecked; entering 0 allows no faults in it.
  5. Select Start and scan the entire display methodically, including its edges. Use Next and Previous, or Space and the arrow keys, to change patterns. If full screen is unavailable, the test uses a full-window view. The control bar hides when idle; move the pointer or select the three-dot handle to show it again. Exit or Escape pauses the session, and Resume continues it.
  6. Mark a repeatable finding by clicking or tapping its location, choosing its type and selecting Add mark. Confirm it on more than one background, but mark each physical fault only once. Record a sub-pixel colour when identifiable. Select an existing mark on its original pattern to edit or remove it; Undo mark removes the latest mark.
    For keyboard marking, press C to toggle the cursor. Arrow keys then move it by one selected-panel-pixel increment, or ten with Shift; Enter opens the mark choices. Toggle the cursor off to use left and right arrows for pattern navigation.
  7. Review Defect log for duplicate or misclassified marks and Pattern coverage for missing backgrounds. The focused backlight, uniformity and banding sequences do not individually provide both black and white. After Exit, change to Full check or Dead and stuck pixels when those backgrounds are still needed; existing marks and viewing history remain until cleared.
  8. Save the Warranty report after checking the findings. Optional model, serial number, purchase date, seller and notes can be added in Advanced. Copy or download the report before reloading or closing the tab, and send it with separately taken photographs when contacting the seller. Clear session and Start again ask for confirmation before clearing marks and pattern history.

Interpreting Results:

The verdict compares your recorded marks with the selected count limits. An empty log means no findings were recorded, not that the browser inspected the display and found it faultless.

  • No limits set means every manufacturer limit is blank. Enter the limits stated for the display before using that comparison.
  • Not checked yet means a required background has not accumulated enough viewing time. ISO and manufacturer checks require black and white; Zero bright dot requires black only. This status takes priority even when an individual criterion already shows Exceeds.
  • Within followed by a policy name means all its applicable count checks pass after the required coverage. Exceeds means at least one does not. Read Policy check to identify that criterion and confirm its marks.

Inspected means a pattern accumulated at least 2 seconds of recorded viewing time. Repeated visits add together; time spent in the mark picker does not count, and hiding the tab pauses the session. This is a tool-specific coverage rule, not an ISO inspection duration or proof that the whole screen was examined. Take as long as needed to scan it carefully.

For evidence you can send or compare, the four result tables support CSV copy and download, DOCX export and individual row copy. The map downloads as PNG, WebP or JPEG, or its plotted coordinates as CSV; the report supports text copy and download.

Lines, bleed or glow, uneven colour or brightness, banding and other findings remain outside the pixel-policy verdict. Review them separately even when pixel counts are within limits. Policy comparison applies alternative policies to the same observations; it does not discover your warranty terms. The Defect map locates your marks and is not a photograph of the display.

Technical Details:

Pixel-count policies distinguish full bright pixels, full dark pixels and faulty sub-pixels. In the terminology used by the ISO-class comparisons, these are Type 1, Type 2 and Type 3 respectively. A per-million allowance scales with the native number of complete pixels, so a higher-resolution display can have a larger absolute allowance under the same rate.

Formula Core

A count passes a per-million limit when the following comparison is true. Equality is allowed.

c × 1000000 ≤ a × W × H

Here, c is the number of marks in the category being checked, a is its permitted count per million pixels, and W and H are the selected panel width and height in pixels. The same complete-pixel denominator applies to sub-pixel rates; it is not multiplied by three.

Comparisons use the exact products without intermediate rounding. The largest accepted whole count is the proportional allowance rounded down. Displayed proportional allowances may be rounded to two decimal places, but those displayed decimals do not decide the result.

ISO-class count comparisons

The following rates match the manufacturer-published table used for the ISO Class presets. Each row gives maximum counts per million complete pixels. Where a class has several rows, the bright and dark sub-pixel counts must fit the same row after scaling; the largest values from different rows cannot be combined.

Preset Bright pixels Dark pixels Bright sub-pixels Dark sub-pixels
ISO Class 0 0 0 0 0
ISO Class I 1 1 2 1
ISO Class I 1 1 1 3
ISO Class I 1 1 0 5
ISO Class II 2 2 5 0
ISO Class II 2 2 4 2
ISO Class II 2 2 3 4
ISO Class II 2 2 2 6
ISO Class II 2 2 1 8
ISO Class II 2 2 0 10
ISO Class III 5 15 50 50

The full bright-pixel and dark-pixel limits are independent checks. The sub-pixel check passes only when both observed sub-pixel counts fit one permitted pair. All three checks must pass, and there is no additional combined-total limit in these ISO-class comparisons.

ISO 9241-307 covers display analysis and compliance test methods beyond this count comparison. Manufacturer publications also differ: some express sub-pixel limits as a weighted total, including for Class III, rather than the separate bright and dark caps shown above. Cluster rules for nearby faults are not applied here. A result therefore cannot establish complete ISO conformity. The actual model's warranty table, rounding rules and inspection conditions govern a claim.

Other policy rules

Zero bright dot requires both the bright full-pixel count and bright sub-pixel count to be zero, regardless of resolution. Dark faults do not fail this check. A real bright-dot guarantee may have additional model and coverage conditions that the count comparison does not evaluate.

Manufacturer limits uses absolute counts for the entire display. Each entered limit must be a whole number from 0 to 999, and the marked count may equal its limit. Every specified limit must pass. Total pixel faults adds the four pixel and sub-pixel categories only; it excludes lines and other broader findings. These controls support category caps and an unweighted total, so they cannot fully reproduce a warranty with weighted sub-pixel totals, cluster restrictions or other special conditions.

Approximate marked positions

A saved location is converted from its fractional position across the displayed pattern to the selected panel grid. Coordinates start at zero in the upper-left corner, increase rightwards and downwards, and are rounded down with the outer edge capped at the final pixel.

x=min(W−1,⌊u×W⌋) y=min(H−1,⌊v×H⌋)

Here, u and v are the horizontal and vertical fractions from 0 to 1, W and H are the selected dimensions, and the floor brackets mean round down. These coordinates locate an observation approximately. Pointer placement, browser scaling and a full-window view can prevent exact alignment with physical pixels. Each saved mark counts once; nearby or repeated marks are not merged automatically.

Accuracy and Privacy Notes:

Repeat observations under consistent settings before comparing runs. The patterns provide visual inspection aids, and the report preserves your observations rather than a hardware diagnosis or warranty approval.

  • The detected resolution multiplies the browser's screen dimensions by its device pixel ratio and rounds each dimension to a whole pixel. This is an estimate that display scaling can still misreport. Selecting dimensions changes the policy calculation and map coordinates; it does not change the monitor's actual resolution.
  • Browser colour management, display settings, ambient light and viewing angle affect the rendered appearance. Grey percentages name digital pattern shades, not measured fractions of the monitor's light output. The Grey steps pattern contains deliberate bands. The 1-pixel checkerboard uses browser layout pixels, which may not map one-to-one to physical pixels and can create moiré.
  • For an uncertain persistent fault, repeat the check with the monitor's own diagnostic procedure where available. The browser test does not repair pixels or supply calibrated luminance or colour measurements.
  • Marks, viewing history and optional report details are processed in the current tab without being uploaded or saved by the tool. Reloading or closing the tab loses them. Setup choices can be restored from the URL, so sharing that URL shares settings rather than findings or personal report details.
  • Starting requests full screen, without camera, microphone or screen-capture access. Copying uses the browser's clipboard facilities, and downloading saves the chosen output. The defect map may need a network connection to load. The report includes the date and browser information as well as any details you enter.

Worked Examples:

Both cases use a confirmed 1920 × 1080 panel with ISO Class I, black and white each recorded as inspected, and no pixel faults beyond those described.

A third dark pixel changes the verdict

The panel contains 2,073,600 pixels. Class I allows one dark full pixel per million, giving an exact proportional allowance of 2.0736 and a maximum whole count of 2. With two dark-pixel marks, the result is Within ISO Class I. Adding a confirmed third changes it to Exceeds ISO Class I. Check the fault classification and actual warranty before using that difference to support a claim.

Fewer sub-pixel faults can still exceed a pair limit

At the same resolution, the maximum whole-count pairs are 4 bright with 2 dark, 2 bright with 6 dark, or 0 bright with 10 dark sub-pixels. Three bright and four dark marks fit none of those pairs, so the result is Exceeds ISO Class I. A separate observation of two bright and six dark marks fits the second pair and returns Within ISO Class I, despite having more marks in total. Keep the bright and dark classifications accurate; their total alone does not decide this comparison.

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