Dead Pixel & Flicker Test Suite

Select a test. Each launches fullscreen. Esc exits. → cycles options mid-test.

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IPS glow diagnostic checklist

  • Test pattern full black, in a completely dark room, at default factory brightness
  • Angle test glow that fades when you look straight on is IPS glow, not backlight bleed
  • Adaptation pause at least 30 seconds before judging the corners
  • Return threshold glow visible at normal seating distance during real dark content, not just on a test pattern

IPS glow diagnostic checklist

  • Test pattern full black, in a completely dark room, at default factory brightness
  • Angle test glow that fades when you look straight-on is IPS glow, not backlight bleed
  • Adaptation pause at least 30 seconds before judging the corners
  • Return threshold glow visible at normal seating distance during real dark content, not just on a test pattern

Bleed pattern types

  • Edge bleed bright band along one or more sides
  • Corner bleed triangular bright region in the corners
  • Clouding diffuse irregular patches, common on VA panels
  • Worm bleed thin streaks a few centimetres into the content area

All patterns stay fixed regardless of viewing angle — that's what separates bleed from IPS glow.

DSE diagnostic checklist

  • Test pattern 50% mid-grey, full-screen, at normal viewing distance
  • Static confirmation scroll content underneath; DSE patches stay fixed to the panel
  • DSE signature irregular blotchy or worm-like patches, not smooth gradients
  • Most affected VA panels, especially 27 to 32 inch and larger

A patch that moves or disappears when you scroll is a cable or driver artefact, not DSE.

DSE diagnostic checklist

  • Test pattern 50% mid-grey, full-screen, at normal viewing distance
  • Static confirmation scroll content underneath — DSE patches stay fixed to the panel
  • DSE signature irregular blotchy or worm-like patches, not smooth gradients
  • Most affected VA panels, especially 27" to 32" and larger

A patch that moves or disappears when you scroll is a cable/driver artifact, not DSE.

OLED retention diagnostic steps

  • Test pattern solid 50% grey, the most sensitive background for faint ghosting
  • Confirm it is real ghost visible at the same location across multiple content types
  • Try first the panel's built-in pixel refresh or self-cleaning cycle
  • Recent vs. old retention short-session ghosts often reverse with cleaning, months-old retention rarely does

OLED retention diagnostic steps

  • Test pattern solid 50% grey — the most sensitive background for faint ghosting
  • Confirm it's real ghost visible at the same location across multiple content types
  • Try first the panel's built-in pixel refresh/self-cleaning cycle (ASUS: ~6 minutes, recommended every 4 hours)
  • Recent vs. old retention recent, short-session ghosts often reverse with cleaning; months-old retention rarely does

Two-pass uniformity test

  • Mid-grey pass reveals broad brightness gradients and DSE-style patches
  • White pass reveals tonal and colour-temperature shifts across the panel
  • Common patterns centre-bright gradient, edge-bright gradient, left-right tonal shift
  • Colour-critical threshold professional standards such as EBU Tech 3320 define explicit chromaticity-uniformity requirements

The same region reading off on both grey and white confirms genuine panel variation rather than a reflection or lighting artefact.

Two-pass uniformity test

  • Mid-grey pass reveals broad brightness gradients and DSE-style patches
  • White pass reveals tonal/color-temperature shifts across the panel
  • Common patterns centre-bright gradient, edge-bright gradient, left-right tonal shift
  • Color-critical threshold professional standards like EBU Tech 3320 define explicit chromaticity-uniformity requirements

The same region reading off on both grey and white confirms genuine panel variation rather than a reflection or lighting artifact.

Diagnosing VRR flicker

  • Common floor many FreeSync panels list a VRR minimum around 48 Hz
  • Confirm it's VRR disable VRR in the GPU driver — if flicker stops, it's a VRR-floor timing issue, not a defect
  • Find your floor test fixed frame caps (60, 55, 50, 45 FPS) and note where flicker starts
  • Fix cap frames a few FPS above the floor, or enable Low Framerate Compensation (LFC)

Windows 11 pre-test checklist

  • HDR Settings > System > Display > Use HDR — disable for baseline SDR tests
  • Night Light Settings > System > Display > Night Light — disable, it shifts white point warm
  • Refresh rate Settings > System > Display > Advanced Display — confirm it matches the monitor spec
  • VRR active check Xbox Game Bar (Win+G) — refresh readout should vary with frame rate, not stay fixed

macOS pre-test checklist

  • True Tone System Settings > Displays — uncheck, it shifts white balance to ambient light
  • Night Shift System Settings > Displays > Night Shift — disable
  • Color profile sRGB IEC61966-2.1 — the standard baseline for colour-sensitive tests
  • External refresh rate macOS sometimes defaults to 60 Hz — confirm the max Hz in the Displays dropdown

IPS glow vs backlight bleed test

  • IPS glow changes with viewing angle — fades when you look straight-on
  • Backlight bleed fixed position and brightness regardless of viewing angle
  • Panels affected virtually all IPS; W-OLED has none (no backlight)
  • Reduces glow A-TW polariser technology (some Nano IPS models)

Both can appear on the same unit — a corner may show bleed at one edge and glow at another.

Backlight bleed patterns

  • Edge bleed bright band along one or more screen edges
  • Corner bleed concentrated around one or more corners
  • Clouding irregular bright patches spread across the panel surface
  • Fixed vs. angle-dependent bleed stays in the same position as viewing angle changes — IPS glow doesn't

Pixel defect types

  • Dark pixel all three subpixels stuck off — black dot
  • Bright pixel all three subpixels stuck on — bright white dot
  • Stuck subpixel one red, green, or blue subpixel stuck on or off
  • Reference standard ISO 9241-307 — the standard most warranty policies cite

A genuine defect stays fixed at the same panel location across all six test colors; dust or reflections move when you clean the screen or shift your angle.

DSE vs other uniformity issues

  • DSE irregular patches, smears, or worm-like streaks fixed to the panel
  • Backlight gradient smooth brightness transition, not patchy
  • Cable/driver artifact moves or changes with signal conditions — DSE never does
  • Most affected VA panels, due to liquid crystal cell alignment sensitivity
Dead Pixel Detection — Solid Color Screens

Left-click or use ← / → to switch colors · Space to show/hide cursor · right-click to mark pixels.

Motion & Ghosting

Press Space mid-test to toggle dark / light background.

Flicker Tests

VRR: press ← / → to change target FPS, ↑ / ↓ for gray shade.  PWM: press Space to switch static / alternating mode.

Color Gradient & Banding
Advanced Tests
Refresh Rate Converter

Enter a refresh rate in Hz to get the frame time in ms, or enter ms to get the Hz equivalent.

Refresh Rate Hz
Frame Time ms
  1. Click any solid color in the Dead Pixel Detection section to launch that test fullscreen — start with Black, then White.
  2. Scan the entire panel slowly from corner to corner. Any fixed dot that differs from the background color is a dead or stuck pixel.
  3. Press Space to show or hide the cursor. Use Left/Right arrow keys to cycle through colors. Right-click to mark a suspect pixel for reference.
  4. Click UFO Ghosting Test — watch the trailing edge behind each orb. A faint smear is normal; a dark halo in front of the orb indicates overdrive overshoot.
  5. Click a gradient test (Horizontal or Vertical) and look for visible bands or stripes across the smooth tonal range.
  6. Use Checkerboard to check sharpness and sub-pixel rendering; use Contrast Patches for near-black and near-white detail.
  7. VRR Flicker: use Left/Right arrows to lower the target FPS (try 24 or 30) and watch a dark gray field for brightness pulsing — a sign your display flickers under VRR.
  8. PWM Flicker: reduce monitor brightness to 25–50%, then aim your phone camera at the screen. Dark horizontal bands in the camera preview indicate backlight PWM flicker. Press Space to switch to alternating mode.
  9. Press Esc at any time to exit fullscreen.
Updated:  ·  Published:  ·  18 min read

How to check a new monitor for dead pixels

A dead pixel is a display cell that has permanently failed. A stuck pixel is powered but locked to a single colour, while a bright subpixel stays fully lit. A dead pixel receives no power and appears as a small fixed black dot on a bright background, and a bright subpixel can appear as a white or coloured dot on a dark screen.1

Monitor test menu with eight solid color screens, ghosting, flicker, gradient and advanced tests, and a refresh rate converter showing 165 Hz
All tests open from one menu: eight solid colors for dead pixels, then ghosting, flicker, gradient and contrast checks. The converter at the bottom turns 165 Hz into a 6.06061 ms frame time.

The correct method: run the Pure Black test and scan every corner slowly. Press Space to show/hide the cursor. Left-click or use ← / → to switch colors. Right-click to mark any suspect pixels. Switch to Pure White, where pixels stuck at black show clearly. Repeat with each primary colour. A stuck subpixel appears as a coloured dot on the other colour screens and vanishes on its own.2

NOTE Dim the room before testing. Dead pixels that are nearly invisible in bright light become obvious in darkness, and the same is true for faint backlight bleed along the edges. Test at your normal seating distance instead of pressing your face against the panel, since faults are easier to judge from where you actually sit every day.2

What can and cannot be fixed

Not every dot you find has the same prognosis. Failed completely, a dead pixel receives no power, stays black on every background, and no software can revive it, so the only cures are a panel replacement or learning to live with the dot. A stuck subpixel is in better shape. It is powered but locked on, and a subpixel in that state sometimes releases after rapid color cycling across the fault, with no guarantee the release happens. Honesty about this suite: it finds and marks faults on solid backgrounds, and it does not include a color-cycling repair mode, so the cycling attempt happens elsewhere if you try it at all.

Where these faults come from is less mysterious than it sounds. Some pixels are faulty from the factory, small defects that slipped past the panel's quality control and reached your desk anyway. Others develop later, when the tiny transistor driving an individual subpixel fails or its connection degrades with age. Finally, physical stress: a panel that takes a knock, or pressure from an uneven mount, can finish off cells that were already marginal. None of these causes is anything you did while testing, and a dead pixel does not spread to its neighbors, which is worth knowing before you start worrying about the count growing.

Burn-in is the fault people fear after finding a pixel problem, and it is a different animal. Where a dead pixel is one failed cell, burn-in is cumulative image retention: static content held on screen for long periods wears an area unevenly, leaving a faint ghost of a taskbar, a map, or a channel logo behind after the content changes. The effect concerns OLED panels far more than LCDs, and it develops across a region rather than appearing as one dot. The OLED burn-in test guide walks the OLED-specific check, and the IPS glow guide separates angle-dependent corner glow from fixed backlight bleed.

A dead pixel check works best as a slow sweep, not a quick glance at one colour. Dead pixels are display elements that have permanently failed and show the wrong colour regardless of the image content. Truly dead pixels appear black because the pixel receives no signal. Stuck pixels show a constant colour, red, green, or blue, and may respond differently to diagnostic patterns. Both types are easiest to find by sweeping through solid colour patterns.1

Running the test systematically

Running a complete dead pixel check requires cycling through each solid colour in a defined sequence rather than a quick glance at one or two patterns. Start with pure red: stuck green and blue sub-pixels appear as coloured dots against the red field, while dead pixels appear as small dark interruptions. Switch to green, then blue, then white; each pattern reveals defects masked against the previous colour.

Sweeping through every solid colour

Finish with the black pattern, which exposes hot pixels and bright sub-pixel failures that a white pattern would conceal. The mid-grey pattern is the most sensitive final pass: sub-pixel defects too faint to register clearly on a pure colour sometimes appear on grey because the luminance contrast sits in the mid-tone range where the eye is most sensitive. Spend at least 30 seconds on each colour and scan all four corners, where defects are easiest to miss at a glance.2

If you find a single defect on one colour but not the others, note exactly which pattern it appeared on; that pattern-specific detail tells support staff which sub-pixel type is affected and whether it matches their defect-classification tables. A defect that vanishes when you switch patterns is a stuck sub-pixel; one that persists across all colours is a full dead pixel and typically carries more weight under warranty policies.

How to confirm a defect is actually fixed to the panel

How to confirm a defect is actually fixed to the panel

Before treating any visible dot or mark as a genuine pixel defect, systematically rule out dust on the screen surface, reflections from ambient light sources, and browser scaling artefacts that can mimic sub-pixel failures when the browser is not rendering at native resolution. Clean the microfibre cloth across the screen, change the test colour pattern, and move the browser window slightly off its current position. A true pixel defect remains fixed at exactly the same panel location regardless of the test pattern or window position, while dust particles move relative to the panel content when you shift the glass or clean it, and reflections shift predictably when you change your viewing angle relative to the light source.

Once the defect is confirmed as panel-fixed rather than a surface artefact, photograph it on the specific test colour pattern where it contrasts most sharply against the background, as this dramatically improves the usefulness of your documentation. A black dead pixel is most visible and clearest on the solid white pattern, a stuck red pixel stands out most on the green or blue patterns where the red subpixel is the only bright element, and a hot or stuck-bright pixel is most visible on the solid black pattern. These precise, pattern-specific notes and photos make warranty discussions significantly more productive and help support staff process your claim faster.

Photographing and documenting defects

Documenting pixel defects before contacting the manufacturer or retailer significantly strengthens your warranty or return case. Photograph the defect while displaying a pattern where the pixel contrasts most visibly: a blue stuck pixel is clearest on a white or yellow background, a dead black pixel stands out on a white field. Use a phone camera at close range without flash in a room with stable, consistent lighting.

When to try pixel cycling first

Stuck pixels, those showing a constant colour rather than black, are sometimes described as recoverable through cycling tools that rapidly switch the pixel through all colour states, but Dell warns that software tools are not officially supported and may not work.1 If a stuck pixel resolves during cycling, it leaves no visible evidence for a subsequent warranty claim. Dead pixels, which appear permanently black, cannot be recovered through cycling because the pixel has stopped working completely.3

Warranty coverage and return decisions

Many monitor warranties set pixel-defect thresholds rather than guaranteeing a perfect panel; ISO 9241-307 defines analysis and compliance test methods for electronic visual displays.4 Dell's standard monitor policy allows several bright pixels or subpixels, while premium programmes like Dell Premium Panel Exchange and ASUS Zero Bright Dot are stricter for bright defects.5 Check your order confirmation or warranty documentation before deciding whether your defect count qualifies.

Why the retailer return window beats a warranty claim

Acting within the retailer return window is almost always faster and simpler than a manufacturer warranty claim, because return windows are typically 14 to 30 days after delivery and require no minimum defect count threshold to qualify. If you find a defect on day one, the retailer return route bypasses the ISO count arguments entirely. Document the defect first with pattern-specific photos, then initiate the return process before the window closes.

Run this test immediately after unboxing before setting up your operating system, ideally as part of this six-colour defect inspection so the same six-colour sweep runs alongside uniformity and refresh-rate checks in one session. Most manufacturer warranty policies require a minimum number of pixel defects before a replacement is approved. Identifying defects within the retailer return window gives you the strongest recourse.25

Finding a stuck red pixel

Before 
Bright red dot visible on the green and blue test patterns
After 
Dot disappears on the red test pattern; it blends in

Run each colour pattern in sequence. A stuck pixel blends into a pattern that matches its stuck colour. Run all six patterns to catch every possible stuck state.

Distinguishing a dead pixel from dust

Before 
Dark spot visible on the white test pattern
After 
Spot remains in the same position across all patterns; confirmed as a dead pixel, not dust

Dust sits on the screen surface and can be removed with a clean microfibre cloth. A dead pixel is inside the panel and stays in exactly the same position on every test pattern.

Sources for this section
  1. 1.

    Dell, "Dell Display Pixel Guidelines," dell.com, accessed June 2026. https://www.dell.com/support/kbdoc/en-us/000126004/dell-display-pixel-guidelines

  2. 2.

    Lenovo, "What if defective pixel is found on your monitor - Policy and Standard, Lenovo Monitors and All-in-One Desktop," support.lenovo.com, last modified April 2026. https://support.lenovo.com/us/en/solutions/ht002800

  3. 3.

    LG, "LG Monitor - Troubleshooting the Monitor Screen," lg.com, August 2024. https://www.lg.com/us/support/help-library/lg-monitor-troubleshooting-the-monitor-screen--20153192527480

  4. 4.

    ISO, "ISO 9241-307:2008," iso.org, November 2008, confirmed 2024. https://www.iso.org/standard/40102.html

  5. 5.

    ASUS, "Zero Bright Dot," asus.com, May 2017. https://www.asus.com/us/support/article/696/

FAQ

A dead pixel receives no power and stays black. A stuck pixel is stuck in an on state and shows a constant colour regardless of the displayed content. Stuck pixels sometimes recover after pixel cycling; dead pixels are permanent.

It depends on the monitor and warranty programme. Some standard policies use ISO-style defect thresholds, while premium bright-pixel programmes such as Dell Premium Panel Exchange and ASUS Zero Bright Dot are stricter. Check your order confirmation, warranty card, or regional support page before assuming a single defect qualifies.

Sometimes, but it is not guaranteed. Pixel cycling tools rapidly switch colours to try to dislodge a stuck pixel; Dell warns that software tools are not officially supported and may not work. Try it before pursuing a warranty claim, but document the defect first in case it remains visible.

CapyToolkit's solid colour patterns cover dead (black), stuck (constant colour), and hot (always-on white) pixel types. Sub-pixel defects, where only one of the three sub-pixels in a pixel cell has failed, are also caught by running all six colour patterns.

Yes. OLED pixels fail differently from LCD pixels; a failed OLED subpixel typically goes dark (dead) rather than stuck. Run the same solid colour sweeps on OLED monitors to check for any dark subpixel anomalies.

Backlight bleed and IPS glow

When a monitor shows bright patches or silvery corners on a dark screen, the cause is usually one of two things: backlight bleed or IPS glow. They look similar at a glance but have completely different origins, and knowing which one you are dealing with determines whether the panel is actually defective or just behaving as its technology dictates.

How backlight bleed happens

LCD panels shine a backlight through a liquid crystal matrix. When the backlight leaks around the panel edges because the frame clamping is uneven, bright irregular patches appear on dark screens. This is a build-quality issue that varies from panel to panel and can worsen if the monitor is subjected to pressure during shipping or storage.3

On a Pure Black test screen, bleed usually shows as brighter corners or cloudy patches along one or more edges. Because it comes from physical light leaking through the panel assembly, its location and intensity stay fixed regardless of where you sit or how you tilt your head, which is the simplest way to tell it apart from IPS glow.

Why IPS glow is different

IPS glow is related but distinct. It is an inherent optical property of IPS panels that produces a silvery shimmer in the corners at oblique viewing angles, and it is present to some degree on nearly every IPS-type panel on the market.4 Run Pure Black in a dark room and compare the two. Bleed shows as bright patches along edges that stay put when you tilt your head, while IPS glow visibly shrinks or shifts with your viewing angle. That angular dependence is the defining characteristic. Extreme bleed that remains visible during normal daytime use may justify contacting the retailer or manufacturer for a replacement.3

Ghosting and pixel response time

Ghosting is the faint trail you see behind moving objects on screen, and it is the most visible symptom of a panel whose pixels cannot keep up with the refresh rate. The underlying cause is response time: the milliseconds each pixel takes to move from one shade of grey to another. A single headline GtG figure rarely tells the whole story because real panels have dozens of possible colour transitions, and some are much slower than others.

What ghosting looks like

Ghosting is the faint trail behind moving objects caused by pixels that cannot transition between states fast enough to keep pace with the frame rate. The response time spec (measured in milliseconds, GtG) quantifies how long a pixel takes to move from one shade of grey to another, but real panels have many possible transitions, so a single headline spec may not describe every worst-case colour change you will actually notice.5

Reading the UFO test pattern

Run the UFO test and watch the trailing edge of each orb against the background. A faint, barely visible smear behind the fastest orb is typical for mid-range panels and is not a defect. A long bright trail that takes several frames to fade is significant ghosting worth noting. A dark halo appearing in front of the orb, known as inverse ghosting, indicates the overdrive circuit is set too aggressively and is pushing pixels past their target colour.5

When to run these tests

Run these tests the same day the monitor arrives, before you mount it, cable-manage around it, or get used to how it looks. Spend at least five minutes working through the full suite while the panel is still in front of you in its out-of-the-box state, so any visible defect is easy to document with plenty of time left on the return window.

If you find a defect, document it while the monitor is still in the relevant test mode. Photograph the screen, note the approximate pixel position relative to the screen edges, and record whether the fault appears on dark or bright backgrounds. Contact your retailer promptly with that evidence in hand, because most return windows are short and a clear photo speeds up the replacement process considerably.

How many pixels is too many is a policy question rather than a physical one, and the answer varies by manufacturer. EIZO, for example, covers fully-lit subpixels under a bright-pixel policy while explicitly excluding dark subpixels, and Dell treats light leakage as a defect only when it significantly affects the viewing experience, so what justifies a replacement under one warranty can be within spec under another.14 Before contacting anyone, find the policy page for your exact model and read it against the evidence you documented above. Lead with the photos and the positions, not with an argument about fairness: a claim that matches the policy's own language moves faster than one that fights it.

PWM backlight flicker and eye comfort

Many LED monitors dim their backlight by switching it on and off rapidly rather than by reducing the current. This technique is called pulse-width modulation, and at low brightness settings the off-periods become long enough that some viewers notice eye strain, headaches, or a visible flicker when they move their eyes across the screen. The test patterns here help you detect whether your display uses PWM and at what brightness it becomes a problem.

How PWM dimming works

Backlight flicker occurs when a monitor uses pulse-width modulation (PWM) to control brightness. Rather than varying the backlight current continuously, a PWM-dimmed panel switches its backlight on and off at high frequency. At low switching rates this flicker may be visible to some users, or it may still cause side effects such as eye strain and headaches during long sessions, particularly at lower brightness settings where the duty cycle is most extreme and the dark intervals between pulses are longest.6 IEEE 1789-2015 treats LED modulation frequencies as a health-risk area and recommends practices to reduce adverse effects for sensitive viewers.7

Detecting flicker with a phone camera

The PWM Flicker test uses a phone camera's rolling shutter to make flicker visible to you. Point your phone camera at the test pattern on the monitor and look for dark horizontal bands scrolling through the camera preview. Their presence confirms that PWM dimming is active at the current brightness.8 Test at 25 to 50 percent brightness, because many monitors use PWM only below a certain threshold and switch to flicker-free dimming above it. Monitors that use DC dimming vary the backlight current directly and avoid PWM-driven rolling bands, which is the preferable behaviour if flicker-related eye fatigue affects you during long work sessions.6

Pixel defect thresholds and the return window

Most manufacturers do not guarantee a perfect panel. Instead they set a defect threshold, and ISO 9241-307 defines the analysis and compliance test methods for electronic visual displays that those policies reference, so a single fault can be within spec for one brand and outside it for another. Check the policy page for your exact model before assuming a dot qualifies.9

Timing matters more than the wording. Retail return windows usually run 14 to 30 days after delivery and require no minimum defect count, so a fault found on day one is almost always faster to resolve through the retailer than through a manufacturer claim. Document the defect first with a photo taken on the pattern where the pixel contrasts most clearly, start the return before the window closes, and note that premium bright-pixel programmes such as Dell Premium Panel Exchange and ASUS Zero Bright Dot are stricter than the standard terms for bright defects in particular.10

Dead Pixel & Flicker Test Suite Reference

  • PWM flicker test brightness 25–50%
  • Ghosting — normal Faint smear behind fastest orb
  • Ghosting — significant Long bright trail across several frames
  • Minimum scan time per color At least 30 seconds

Run the PWM Flicker and UFO Ghosting tests above and compare what you see against this scale.

Sources
  1. 1.

    EIZO, "Warranty & Recycling Information," eizo.com, accessed June 2026. https://www.eizo.com/warranty/

  2. 2.

    EIZO, "EIZO Monitor Test," eizo.com, accessed June 2026. https://www.eizo.com/library/basics/eizo-monitor-test/

  3. 3.

    TFTCentral, "Terms and Functions," tftcentral.co.uk, accessed June 2026. https://tftcentral.co.uk/features

  4. 4.

    Dell, "How to Distinguish IPS Glow and Light Leakage in a Dell Monitor," dell.com, accessed June 2026. https://www.dell.com/support/kbdoc/en-aw/000318297/how-to-distinguish-ips-glow-and-light-leakage-in-a-dell-monitor

  5. 5.

    Nicholas Di Giovanni, "Our Monitor Motion Tests: Response Time," rtings.com, April 2026. https://www.rtings.com/monitor/tests/motion/motion-blur-and-response-time

  6. 6.

    Simon Baker, "Pulse Width Modulation (PWM)," tftcentral.co.uk, March 2015. https://tftcentral.co.uk/articles/pulse_width_modulation

  7. 7.

    IEEE, "IEEE 1789-2015: IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers," standards.ieee.org, June 2015. https://standards.ieee.org/ieee/1789/4479/

  8. 8.

    Libo Zhu et al., "Combined Flicker-banding and Moiré Removal for Screen-Captured Images," arxiv.org, accessed June 2026. https://arxiv.org/html/2602.01559v1

  9. 9.

    ISO, "ISO 9241-307:2008," iso.org, November 2008, confirmed 2024. https://www.iso.org/standard/40102.html

  10. 10.

    Dell, "Dell Display Pixel Guidelines," dell.com, accessed June 2026. https://www.dell.com/support/kbdoc/en-us/000126004/dell-display-pixel-guidelines

FAQ

A dead pixel gets no power and appears as a permanently black dot. A stuck pixel is powered but locked to one colour. On the pure black test, stuck pixels show as a coloured dot. Dead pixels are easier to spot on the white or solid-colour screens.

Yes. The tests are designed to cover your entire display so you can scan every corner and edge without the browser UI getting in the way. Use the fullscreen button before running any pattern.

As dark as you can manage. Dead pixels that are nearly invisible in daylight become obvious in low light. The same applies to backlight bleed.

It depends on the behaviour. If the patches shrink or shift when you tilt your head, that is IPS glow, an inherent property of IPS panels and not a fault. If they stay fixed regardless of viewing angle, that is backlight bleed, which can be a warranty claim if severe enough to be visible in normal use.

Yes. Open the tool on your phone and ask a staff member to load the URL on the display you want to check, or cast from your phone. You can run the solid-colour dead pixel tests right there in the store.

At least 30 seconds per colour, longer on the black screen. Your eyes need time to adjust and scan the full panel. Rushing the dead pixel check is the most common reason people miss faults until after the return window closes.

Additional resources

Dead Pixel & Flicker Test Suite Reference Every display artifact the suite tests for, dead pixels, backlight bleed, ghosting, and more, with identification criteria and what actually causes each one. Dead Pixel & Flicker Test Suite: Code Examples Windows 11 and macOS setup guides for HDR, Night Light, refresh rate, and VRR configuration, so the readings the suite gives you actually match your display settings. Dead Pixel & Flicker Test Suite: Conversions Hz to ms and ms to Hz refresh-rate math, worked out for common gaming monitor refresh rates so you know the frame time before you run a test.

Guides

IPS Glow Test and Per-Model Notes Check IPS glow and backlight bleed on a budget or premium IPS panel, and see what changes on the Acer Nitro XV272U, ASUS ROG Swift PG279QM, BenQ MOBIUZ EX2710S, Dell UltraSharp U2724DE and S2721DGF, Gigabyte M27Q3, LG 27GP850-B, 27GR83Q-B and 27GR93U and MSI MAG274QRF-QD. Backlight Bleed Test - How to Check Your Monitor Check your monitor for backlight bleed using a full black test pattern. Identify edge and corner bleed before your return window closes. Dirty Screen Effect Test and Per-Model Notes Check a VA panel for dirty screen effect on a mid-grey test pattern, and see what changes on the Dell S2722DGM, Samsung Odyssey G3 and Odyssey G7 and AOC C27G2Z. OLED Burn-In Test and Per-Model Notes Check an OLED monitor for image retention and early burn-in on a grey test pattern, and see what changes on the Alienware AW2725D and AW2725DF, ASUS ROG Swift PG27AQDP and PG27UCDM and Samsung Odyssey OLED G5. Monitor Uniformity Test and Per-Model Notes Check a monitor for backlight uniformity on grey and white patterns, and see what changes on the AOC Q27G3XMN and Samsung Odyssey Neo G7 32 inch, two mini-LED VA panels. VRR Flicker Test - Check for Variable Refresh Rate Artifacts Check your monitor for FreeSync or G-Sync flicker at low frame rates. Diagnose VRR range floor issues before adjusting your GPU settings.