Monitor Test
Check your screen for dead/stuck pixels, backlight bleed, ghosting and panel uniformity - a free visual self-check that runs 100% in your browser.
What this checks: Four visual self-checks that run in your browser: dead and stuck pixels (eight solid colors, a per-pixel gradient and a random-pixel view), backlight bleed (black and dim-gray fields), ghosting (a moving square at a speed you set) and panel uniformity (an eleven-step gray ramp).
Everything runs on this device in your browser. Nothing is uploaded, no camera is accessed and no account is needed.
This is a visual self-check. You are the instrument: what you see depends on the room, the angle and your eyes. A "clean" run is not a panel defect certificate, and a suspect pixel you see here is worth checking again - it is not a confirmed defect.
Setup
- Dim the room: close the blinds, switch off ceiling lights and use low monitor brightness.
- Sit about 60 cm away and let the panel warm up for 30 seconds before you start judging it.
- Look at the edges, corners and the area around the ports on the black field first, then compare with the dim-gray field.
What to look for
- Dead pixel: permanently off - it shows as a white point on the black field or a black point on a colored field.
- Stuck pixel: stuck at one color on every field - it never matches the color around it.
- Off-white pixel: looks faintly colored instead of pure white - easiest to spot on the white and gray fields.
- Start the solid-color field and go full-screen, then step through all eight colors with the swatch strip.
- Scan the whole panel - center, edges and corners - and check every suspect spot on several colors before you call it.
- Switch to the gradient and the random-pixel view: they expose suspect pixels that hide on a single solid color.
Backlight bleed
Watch for patchy bright spots at the edges and corners. Some even, faint edge glow is normal on IPS-type panels - note it, judge it, but do not panic over it.
Ghosting
Watch for a faint smear or trail behind the moving square - that is ghosting. The square bounces left to right at the speed you set; the higher the speed, the more response time the panel has to hide it.
Reduced motion is on: the ghosting object stays stationary so you can still inspect the fields. Turn off reduced motion in your system settings to watch it move.
Uniformity
Eleven gray steps from pure black to pure white, one column per step with 1-pixel separators, spanning the full viewport height.
Watch for banding - visible steps or stripes inside what should be a flat column - and for non-uniform brightness, for example brighter corners or a brighter center than the edges.
How to use the Monitor Test
How to run each mode
- Dead / stuck pixel: start the mode, go full-screen, and step through the eight solid colors, the gradient and the random-pixel view. Scan the whole panel - center, edges and corners - and re-check every suspect spot on several colors.
- Backlight bleed: dim the room and start the black field. Wait the full 30-second warm-up before you judge the edges, corners and the area around the ports.
- Ghosting: pick a speed and start. A faint smear or trail behind the moving square is slow pixel response; the side-by-side compare shows both fields at once with a single shared clock.
- Uniformity: start the mode and read the eleven gray columns for banding (visible steps inside a flat column) and brightness differences between the center and the edges.
Tips
- Full-screen is the honest view: browser pixels map one-to-one to screen pixels only in full-screen, so a windowed check covers just the area the window occupies.
- Even, faint edge glow on IPS-type panels is normal after warm-up; patchy or bright spots are not. Note what you see and where.
- If your system requests reduced motion, the ghosting object stays stationary so you can still inspect the fields - the static modes are unaffected.
This is a visual self-check. You are the instrument: what you see depends on the room, the angle and your eyes. A "clean" run is not a panel defect certificate, and a suspect pixel you see here is worth checking again - it is not a confirmed defect.
Use cases
Five situations where a five-minute self-check pays off before money changes hands.
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Before you keep a new monitor
Run all four modes right after unboxing, while returns are free. A dead pixel found in week one is a no-questions replacement; the same spot in month six is an argument.
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Second-hand purchase check
Bring the monitor test to the deal: open the dead-pixel solid fields and the uniformity ramp before you pay. Bleed and ghosting are visible only on the actual panel, so the seller can't demo their way past it.
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Troubleshooting before an RMA
When a spot on screen looks off, the eight solid fields and the random-pixel view separate a dead pixel from a stuck one and from a dust speck on the glass - most of the time, before you ever open a support ticket.
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Comparing two panels
New panel versus the old one on the same desk: run the same gray ramp and the same ghosting speed on both and look at them back to back. Differences in bleed, uniformity and smearing become obvious that way.
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After a cable or settings change
Swapped the cable, the refresh settings or the output device? A quick pass over the solid fields and the uniformity ramp takes a minute and rules out the obvious before you chase the rest of the stack.
Frequently asked questions
- Why does the monitor test ask me to be full-screen?
- Because windowed pixels are not the whole screen. Full-screen makes every browser pixel map one-to-one to a screen pixel, so the solid fields, the gradient and the uniformity ramp cover the entire panel - including the edges, where most suspect pixels hide.
- How do I know if a pixel is dead or stuck?
- A dead pixel is permanently off: it looks like a white point on the black field or a black point on a colored field. A stuck pixel is stuck at one color: it shows the same color on every field, never matching its neighbors. A pixel that looks faintly colored on white is an off-white pixel - the easiest one to confirm, and the easiest to miss.
- Is backlight bleed a defect?
- Not always. Some edge glow in the corners and around the ports on a black field is normal on many IPS-type panels, especially at low brightness. Patchy, bright or uneven spots - or bleed that gets worse the more you look - are the ones worth logging, and they are always worth checking before you keep the panel.
- What is ghosting?
- Ghosting is slow pixel response: a moving image leaves a faint smear or trail behind it. The ghosting mode moves a square at a speed you set, so you can compare the light-on-dark field, the dark-on-light field and both at once to see whether your panel keeps the edge crisp or smears it.
- Why is there no automatic score?
- Because you are the instrument. A browser can paint the fields, but it cannot see your panel from your chair in your light. The test shows the fields and tells you what to look for; the verdict is yours, which is also why there is nothing to upload and no account to create.