Dead Pixel Test
Fill the screen with five solid colors to spot dead, stuck and hot pixels.
Monitor Test
Check any monitor, laptop, phone or TV screen by filling it with one solid color at a time. Against a flat field, a tint, a blotch, a line or a dot that stays the wrong color is easy to see.
Showing Black
Keys: ← → color · F full screen · A auto cycle · Esc exit
Runs entirely in your browser. Test results, audio and video never leave your device.
How to run the monitor test
- Clean the screen, use your usual brightness and turn off Night light or any blue-light filter, which tints white.
- Press Start test, or click or tap the test area, to fill the screen.
- Move through the colors with Next and Previous, the Left and Right arrow keys, Space, Enter or a tap, or press A to cycle through them every 3 seconds. While the test fills the screen, the keys 1 to 9 and 0 jump straight to a color; before you start, the color buttons pick one, and F starts the test.
- On each color, look across the whole panel from your normal viewing position, including the edges and corners.
- Dim the room for Black and Near black 5%: light leaking at the edges and patchy glow show most clearly in the dark.
- Press Esc or Exit when you are done.
What to look for
- A tint or color cast, such as white that looks yellow, blue or pink.
- Blotches, bands or darker corners on White and Gray 50%.
- Dots that stay black, lit or the wrong color while the rest of the screen changes.
- Lines or stripes that cross the panel in the same place on every color.
- Light at the edges or patchy glow on Black and Near black 5% in a dim room.
What is a monitor test?
A monitor test is a set of full-screen patterns that make display faults visible to the eye. Solid colors come first, for tint, blotches, lines and faulty pixels. Gradients then show banding, dark fields show backlight bleed and glow, and moving patterns show blur and ghosting.
A full monitor check, in order
Solid colors are the first pass. For a new screen while you can still return it, or a used one before you pay, continue in this order:
- Solid colors on this page: tint, blotches, lines and obvious faults. For a particular shade or a custom hex color, use the Screen Color Test.
- The Dead Pixel Test: dots that stay black, lit or one color whatever color fills the screen.
- The Screen Uniformity Test and the Backlight Bleed Test, in a dim room: patches on gray, and light leaking at the edges of a dark screen.
- The Contrast Test and the Gamma Test: black level, white clipping, gamma and shadow detail.
- The Gradient Test: steps or bands in smooth gradients.
- The Refresh Rate Test and the Ghosting Test: whether the screen runs at its rated refresh rate and how clean motion looks.
Laptop, phone or TV screen
- Laptop: connect an external monitor and compare. A fault that shows on the built-in screen but not on the external one points to the built-in display: the panel or its cable. One that shows on both points to the laptop's settings, graphics driver or graphics hardware.
- Phone: turn off automatic brightness if your phone allows it, so the level does not change mid-test. Some phone browsers, including Safari on iPhone, keep their toolbar on screen, so the strip under it is not tested.
- TV: open this page in the TV's web browser. Where the remote's OK button acts as Enter or as a click, it moves to the next color. Many TVs also have a picture test of their own in the support or self-diagnosis menu.
Normal or a defect?
Some unevenness is normal, especially on LCD screens. What matters is whether you notice it in everyday use, not only on a test pattern in a dark room.
| What you see | Usually | What to do |
|---|---|---|
| A slightly darker edge or corner on white or gray | Normal on LCD screens | Nothing, unless you notice it in normal use |
| A glow in the corners of a black screen that changes as you move your head | IPS glow, common on IPS screens | Check it again at your usual brightness and seat |
| Light leaking along an edge that stays put when you move | Backlight bleed | Run the Backlight Bleed Test; consider a return if it shows in dark scenes |
| A dot that stays black, white or one color | A dead, stuck or hot pixel | Count it and read the maker’s pixel policy; see dead vs stuck pixels |
| A line across the screen, or a patch that never changes | A panel or cable fault | Try another cable and input, then contact the seller while the return window is open |
How it works
The page paints the test area with one flat CSS background color at a time: Black, White, Red, Green, Blue, Yellow, Cyan and Magenta at full 8-bit values such as #ff0000, then Gray 50% (#808080, level 128 of 255) and Near black 5% (#0d0d0d, level 13). No image, video or canvas is involved, so nothing is scaled or compressed.
Start test uses the browser's Fullscreen API, or a fixed overlay where it is not available. The controls and pointer hide after 2.5 seconds without input, and a tap that only wakes them does not change the color. Nothing is measured: you judge what you see.
Limitations
- It makes faults visible to your eyes. It cannot measure brightness, color accuracy or response time, and it cannot repair anything.
- Brightness, picture mode, viewing angle and room light all change what you see, so test at the settings you normally use.
- A slight fall-off toward the edges, and some glow on black in a dark room, are common on LCD screens and usually not a defect. Faults you notice in everyday use matter more than ones you have to hunt for.
Frequently asked questions
Do monitors have a built-in self-test?
Many do. On some, unplugging the video cable brings up a message or pattern drawn by the monitor itself; others have a diagnostics item in the on-screen menu. If that looks clean but your computer's picture does not, suspect the cable or the computer. On many Dell laptops, holding D while pressing the power button runs the screen's own color test.
How do I know if my monitor is failing?
Lines, blotches or dim areas that stay in the same place on every color point to the panel. Flicker, a picture that drops out or random sparkles can also come from the cable, the port or the graphics output, so try another cable and input before you blame the monitor.
Can a monitor test check my refresh rate or resolution?
Not with solid colors, but other tests can. The Refresh Rate Test estimates the refresh rate from how often the browser draws frames, and the Screen Resolution Test shows the resolution and pixel ratio the browser reports.
Does a monitor test work on an OLED screen?
Yes. OLED pixels switch off for black, so Black shows no glow at all, which is normal. Near black 5% is the more useful dark field: look for uneven shades or bands on it. For ghost images left by static content, use the Screen Burn-In Test.