Monitor Test

What to look for

Each pattern in the new monitor check, what's normal, and what it can't tell you.

1. 1. Black

   On screen

   The whole screen is pure black, RGB 0, 0, 0.

   Look for

   Lit dots that stay bright on black. A dot that glows white, red, green or blue here is a stuck subpixel or pixel.

   Usually normal

   A faint glow at the edges or corners of an LCD in a dark room is backlight bleed or IPS glow, not a pixel fault. Dust on the screen moves when you wipe it.

   Can't tell you

   The browser can't see your panel, so it can't tell a stuck pixel from a speck of dust or a reflection. Only your eyes can.

2. 2. White

   On screen

   The whole screen is pure white, RGB 255, 255, 255.

   Look for

   Dark dots that stay black on white. A dot that's black on every color is a dead pixel.

   Usually normal

   Small brightness changes across a large white field are common, especially near the edges.

   Can't tell you

   Brightness and color depend on your monitor settings and the room. This isn't a brightness or white point measurement.

3. 3. Red

   On screen

   The whole screen is pure red, RGB 255, 0, 0.

   Look for

   Dots that look black, green or blue instead of red. A dark dot here but not on white means the red subpixel is out.

   Usually normal

   Red can look slightly orange or pink depending on the panel's color space and the monitor's picture mode.

   Can't tell you

   This doesn't check color accuracy. It only makes each red subpixel light up so you can spot one that doesn't.

4. 4. Green

   On screen

   The whole screen is pure green, RGB 0, 255, 0.

   Look for

   Dots that look black, red or blue instead of green. Green subpixels are the brightest, so a dead one is easy to see here.

   Usually normal

   Wide gamut monitors can show a very saturated, almost neon green. That's the panel, not a fault.

   Can't tell you

   This doesn't check color accuracy. It only makes each green subpixel light up so you can spot one that doesn't.

5. 5. Blue

   On screen

   The whole screen is pure blue, RGB 0, 0, 255.

   Look for

   Dots that look black, red or green instead of blue. Blue is the darkest primary, so look closely.

   Usually normal

   Pure blue looks darker than red or green. Slight unevenness on blue is hard to judge and often normal.

   Can't tell you

   This doesn't check color accuracy. It only makes each blue subpixel light up so you can spot one that doesn't.

6. 6. Gray

   On screen

   The whole screen is a flat neutral gray at RGB 128, about 50% of full white.

   Look for

   Darker or lighter patches, a tint that changes across the screen, vertical or horizontal bands, or a dirty, smudged look when you move your head.

   Usually normal

   Some falloff toward the corners is common on LCDs, and curved or large screens look less even from a close seat. Small changes you only see on a flat gray rarely show in normal use.

   Can't tell you

   This is a visual check, not a uniformity measurement. Room light, viewing angle and screen reflections all change what you see. Measuring uniformity takes a colorimeter.

7. 7. Dark gray

   On screen

   The whole screen is a very dark neutral gray at RGB 26, about 10% of full white.

   Look for

   Clouding, bright patches near the edges, and on OLEDs, faint vertical bands or a blotchy look that only shows near black.

   Usually normal

   Some near-black unevenness is normal on many OLED and LCD panels, and it's much easier to see in a dark room than in daily use.

   Can't tell you

   Near-black results swing a lot with brightness, local dimming, and the room. Treat what you see as a reason to look again with normal content, not a verdict.

8. 8. Gray gradient

   On screen

   A smooth gradient from black to white, running left to right.

   Look for

   Visible steps or bands instead of a smooth blend, and color tints in what should be pure gray.

   Usually normal

   A gradient across a wide screen has only 256 levels per channel in an 8-bit signal, so faint banding can be normal, especially in the dark part.

   Can't tell you

   Banding can come from the browser, the graphics driver, color profiles, display scaling, the cable signal or the panel. This pattern shows banding but can't say which step caused it.

9. 9. Color gradients

   On screen

   Four smooth gradients from black to red, green, blue and white, running left to right.

   Look for

   Steps or bands in any of the four ramps, and a ramp that clips to full color too early.

   Usually normal

   Banding is often easier to see in one channel than the others. Faint steps are common on 8-bit signals.

   Can't tell you

   Like the gray gradient, this shows that banding exists somewhere in the chain, not where it comes from.

10. 10. Gray steps

    On screen

    32 labeled patches from black (0) to white (255) in even steps.

    Look for

    Two neighboring patches that look the same, which means the screen merges those levels, and patches with a color tint.

    Usually normal

    The darkest steps can be hard to tell apart in a bright room. Steps that look evenly spaced aren't required, since screens follow a gamma curve.

    Can't tell you

    This uses code values, not measured brightness. It can't check gamma or calibration.

11. 11. Near-black steps

    On screen

    16 labeled patches with code values 1 to 16 on a pure black (0) background.

    Look for

    How many of the dim patches you can tell apart from the background. Many monitors show the first visible patch somewhere in the low single digits.

    Usually normal

    Not seeing the faintest patches is common, especially on LCDs in a lit room or with a low brightness setting.

    Can't tell you

    This isn't a black level, contrast or HDR test. Your monitor settings, graphics driver range setting (full vs limited) and room light all change the result.

12. 12. Near-white steps

    On screen

    16 labeled patches with code values 239 to 254 on a pure white (255) background.

    Look for

    Whether the brightest patches blend into the background. If several vanish, highlights are clipping.

    Usually normal

    The patches closest to 255 are often very hard to see, even on a good screen.

    Can't tell you

    This uses code values, not measured brightness, so it can't confirm calibration or HDR highlight handling.

13. 13. Sharpness

    On screen

    Fine line pairs, a one-pixel checkerboard and small text in black and white. The lines are drawn one canvas pixel wide to match device pixels where the browser allows it.

    Look for

    Line pairs that look gray, blurry or wavy instead of crisp, color fringes around text, and soft edges that suggest the image is being scaled.

    Usually normal

    Fine patterns can shimmer or show moire on some screens, and text has some color fringing with subpixel antialiasing.

    Can't tell you

    Browser zoom, operating system scaling and a non-native resolution all blur these patterns. If they look soft, check that the monitor runs at its native resolution and zoom is 100% before blaming the panel.

14. 14. Motion

    On screen

    High contrast blocks and a line of text move left to right at 960 CSS pixels per second over black, gray and light bands. Space pauses and plays it.

    Look for

    Trails behind the moving blocks, bright or dark halos around edges (overshoot), and text you can't read while it moves.

    Usually normal

    Every screen blurs moving objects a bit when your eyes follow them. Faint trails at high speed are normal, especially on LCDs at 60 Hz.

    Can't tell you

    This shows what you see, not a response time or input lag number. The browser's frame delivery, your refresh rate and variable refresh all change it. A photo or screen recording of it doesn't prove anything about the panel.

Limits of any browser test

• A browser can't read your panel. Every result here is what you see, not a measurement.
• It can't measure brightness, contrast, color accuracy, response time or input lag. That takes a colorimeter or dedicated hardware.
• Browser zoom, operating system scaling, HDR mode, color profiles and the monitor's picture settings all change what the patterns look like.
• It doesn't repair pixels, and passing it isn't proof for a warranty claim. Check the maker's pixel policy for that.