A monitor can look perfect in a product photo, then reveal a bright dot, a crushed-black corner, or a distracting motion trail on your desk. Check the actual monitor, laptop, TV, or phone before the return window closes or before you pay for it used.
Use the free Screen & Monitor Test to run each pattern locally in your browser, with no upload and no sign-up required. The guided check can export a local inspection report with notes and marked defect coordinates.
Set up the inspection properly
Give yourself enough time to test the panel before deciding. For a new display, do it soon after delivery while an exchange is still straightforward. For a used monitor, test it on-site and inspect the exact device you will take home.
Start with these basics:
- Let the panel warm up and use its normal resolution.
- Remove windowed apps and notifications that could obscure the pattern.
- Test in normal room light first, then repeat black-screen checks in a dim room.
- Keep a note of anything you see: color, location, test pattern, and whether it moves when you change viewing position.
For a dead-pixel check, get close enough to scan the whole surface methodically. For uniformity and bleed, step back to your usual viewing distance. The two viewing distances answer different questions.
1. Look for dead, stuck, and bright pixels
Open the dead pixel test and cycle through the solid fields. A completely dead pixel stays black, so it is easiest to spot on white or bright color. A stuck sub-pixel stays red, green, blue, or a combination of those colors, and usually stands out against black or a complementary field. A persistent bright point is easiest to spot on a dark field.
Check black, white, red, green, blue, cyan, magenta, yellow, and grey. A single background can hide a fault that another makes obvious. If you find a defect, use the on-screen marker and record its coordinates.
A flashing stuck pixel fixer may help a stuck pixel, but it cannot repair a genuinely dead pixel with a damaged electrical path. The fixer uses a movable patch by default so you can target the affected spot. It flashes rapidly, so read the photosensitivity warning and do not use it if flashing images are unsafe for you.
2. Separate backlight bleed from IPS glow and clouding
Open the backlight bleed test, set the screen brightness high, and dim the room. Look for bright, fixed streaks around an LCD's edges or corners. That is the typical shape of backlight bleed, which is associated with physical pressure or fit in the panel assembly.
Then move your head slightly, or change your viewing angle. A diffuse pale haze that shifts, changes shape, or fades as you move is more consistent with IPS glow, an angle-dependent characteristic of IPS panels. Irregular brighter areas across the centre of a dark or grey field can indicate clouding or non-uniformity.
Use the monitor uniformity test for grey and white fields. It is useful for finding patches that a black screen alone will not show. OLED does not use an LCD backlight, so backlight bleed is not the right diagnosis for an OLED panel.
3. Check gradients, shadows, and highlights
Run the color banding test and look at the grey, RGB, and near-black ramps. You are looking for abrupt steps, tinted sections, or crushed shadow levels where a smooth change should be visible. The test presents 256 equal steps, which makes uneven transitions easier to see.
This is a visual quality check, not a color-depth detector. A browser pattern cannot prove that a panel is true 10-bit. It can show whether the signal chain and display make the supplied ramps look uneven.
Follow it with the contrast and gamma patterns in the main tool. Very dark steps that merge into black suggest shadow detail is being clipped. Very bright steps that merge into white suggest highlight clipping. These can be caused by settings as well as the panel, so note your picture mode before changing anything.
4. Watch motion and refresh behaviour
Open the ghosting test and watch the moving object against its different backgrounds. A soft dark trail behind it points to a slow pixel transition. A bright or inverted halo can indicate overdrive overshoot. A clean edge without a visible trail is the target.
Then run the refresh rate test. It measures the cadence that this browser receives with requestAnimationFrame, and shows frame timing, jitter, missed frames, and a moving pattern for spotting tearing. Treat that reading as a browser-session measurement, not a certified panel specification: background tabs, power-saving modes, privacy settings, and multi-monitor behaviour can limit it.
Turn findings into a useful return or seller conversation
Finish the guided check and save the inspection report as text or PNG. It keeps the device details, results, notes, and marked defect locations together. That gives you clearer evidence than "there is a dot near the left side."
The report does not decide whether a seller must accept a return. Pixel-defect coverage differs by model, region, retailer, and manufacturer policy. Still, it gives you a reproducible record of what was visible, where it was visible, and which test exposed it.
Judge faults where you actually use the display. A minor imperfection visible only from inches away on a test field may not matter. A bright centre pixel, persistent edge bleed during dark games, or obvious text smearing may matter every day.