Utility · Screen & OLED testing
Test a screen with plain fields of colour
Open a pure black, white or primary-colour field full screen and look at the panel instead of at a picture. Dead pixels, backlight bleed, banding and dust all show up on a flat field, and the colour-cycle mode keeps an OLED panel evenly worn. Every test also works from the URL hash, so the page still works with JavaScript turned off.
What each test is for
eight fields, no picturesA flat field of one colour is the only image that isolates the panel from the content. Everything below is a full-bleed field with nothing drawn on top of it, so anything you see comes from the screen and not from the page.
| Field | What it is for | When to use it | How to read the result |
|---|---|---|---|
| Black | Panel uniformity and how black the panel can go | First test on any screen, in a dim room | Bright corners, a cloudy patch or horizontal bands point to backlight bleed or local-dimming zones |
| White | Brightness and colour evenness, plus dust on the panel | Straight after the black field | Dim corners, colour patches or specks that move when you tilt the screen are dust, not dead pixels |
| Red, green, blue | Dead and stuck subpixels | When you suspect a faulty pixel | A dot that stays dark is a dead subpixel; a dot that stays lit is a stuck one. Blue ages first on OLED |
| Grey ramp | Banding and gradient dithering | When gradients or skies look striped | Visible steps instead of a smooth blend mean the panel or the GPU is quantising the ramp |
| Checkerboard | Sharpness, scaling and moire | When text or fine detail looks soft | Soft, shimmering or rainbow edges mean the panel or the scaler is filtering the image |
| Colour cycle | Even wear across an OLED panel | Any session longer than a few minutes | Nothing to read. It rotates the primary colours so no subpixel carries the whole load |
Before you start
five minutes of setup- Clean the panel with a dry microfibre cloth. Dust and fingerprints look exactly like a bright dot on a black field.
- Dim the room. Backlight bleed and clouding are invisible in a bright room and obvious in a dark one.
- Let the panel run for a few minutes first. A cold panel shifts in brightness and colour while it warms up.
- Sit at your normal distance and look at the whole field, not at one spot. Uniformity problems are about the panel as a whole.
- Turn off night light, HDR, adaptive brightness and any dark-mode extension, because all of them change what reaches the screen.
Start a test
links work without JavaScriptEach button is an ordinary link to a hash. With JavaScript the field also opens full screen; without it, the field is drawn on this page from the same hash, so the tool still works and the link can still be bookmarked or shared.
Full screen needs a click, so a shared link opens the field on the page instead.
Keyboard shortcuts
when the page has focus| Key | Opens | Hash |
|---|---|---|
| B | Black field | #black |
| W | White field | #white |
| R | Red field | #red |
| G | Green field | #green |
| U | Blue field | #blue |
| A | Grey ramp | #grey |
| C | Colour cycle | #cycle |
| X | Checkerboard | #checker |
| 1 to 8 | The same eight fields, in the order listed above | #black to #cycle |
| Esc or Q | Leave full screen and clear the test | no hash |
Blue uses U and the grey ramp uses A, because B and G are already taken by black and green. If your system asks for reduced motion, the colour cycle holds on its first colour instead of animating.
Test field
no test runningPick a test above. The field is drawn from the URL hash, so it also opens on its own with JavaScript turned off.
No test running · 00:00
OLED warning. Leaving a high-contrast static image on an OLED panel for a long time risks burn-in, and the damage is permanent. Use the colour-cycle mode, keep sessions to a few minutes, and never leave a full-screen field running unattended. LCD panels do not burn in, but a long session still wastes power and wears the backlight.
How to use Display Test
Everything below runs in this tab. Nothing is uploaded, and no account is needed.
Step by step
- Read What each test is for and pick the field you need. Every button is a plain link to a hash, so it works even with JavaScript turned off.
- Press a mode button or a keyboard shortcut. The field opens full screen when your browser allows it, and stays in the page when it does not.
- Give the panel a minute to settle in a dim room, then look for dots that do not match the field, bright patches, or steps in the grey ramp.
- Watch the elapsed timer and keep sessions short. On an OLED panel use the colour-cycle mode for anything longer than a few minutes.
- Press Esc or Q to leave, or tick Hide the interface to keep only the field, the timer and that toggle on screen.
Details and limits
Dead pixel versus stuck pixel
A dead subpixel has lost its connection and never lights, so on a black or single-colour field it shows as a dark dot that never changes. A stuck subpixel is switched on permanently, so it shows as a bright dot of one colour, or as a white dot when all three are stuck. On an OLED panel the same rule applies per subpixel, and a cluster of dead pixels usually means a damaged panel rather than a manufacturing fault.
What a black field tells you
With the room lights down, a full black field shows how evenly the panel can go dark. Bright corners or edges, a cloudy patch or horizontal bands point to backlight bleed on an LCD, to local-dimming zones stepping, or to a panel that is simply not very black. A little glow at the edges is normal on IPS panels; a large bright wedge in one corner is not.
Why OLED panels need the cycle mode
OLED subpixels make their own light and dim by being driven less, so the blue subpixels age fastest and fixed, high-contrast content such as taskbars, logos and news tickers wears a permanent shadow into the panel. That shadow is burn-in and it does not go away. Rotating the primary colours spreads the dose evenly, and short sessions keep the total dose down. Panels ship with pixel shifting and brightness limiting that help, but they do not remove the risk.
What a browser test cannot measure
This page can put a flat field on the screen and nothing more. It cannot measure luminance, colour accuracy, gamma, contrast ratio, response time, or uniformity in numbers, and it cannot tell you whether a dot is one subpixel or three. Your operating system also transforms the output: colour profiles, night light, HDR tone mapping and adaptive brightness all change what reaches the panel. For figures, use a colorimeter and calibration software.
Check a colour pair for contrast · Read the guide on pixels, DPI and print size · Install for offline use
Frequently asked questions
How do I test a screen for dead pixels?
Open the black field, then the red, green and blue fields in turn, in a dim room. A dead subpixel shows as a dot that stays dark on every field, and a stuck subpixel shows as a dot that stays lit in one colour. One or two stuck subpixels are common and usually invisible in normal use; a cluster of them is a warranty matter.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel has no signal reaching it, so it stays black on every field. A stuck pixel is permanently on, so it stays red, green, blue or white whatever the field shows. Both are easiest to see on a flat field, which is why this tool has one colour per screen with nothing else drawn on it.
How long should I run a burn-in check?
Keep it short. Fifteen to thirty minutes of the colour-cycle mode is enough to see whether a panel has retained an image, and running a static high-contrast field for hours is exactly what causes burn-in on OLED. If you suspect retention, switch to the cycle mode, take a break, and look again the next day.
Does it work on a phone or a tablet?
Yes. The field fills the viewport on a touch screen, and the mode links work as ordinary links, so you can open a field straight from the browser or from a home-screen shortcut. The keyboard shortcuts need a physical keyboard, so on a phone use the buttons and the elapsed timer instead.
Can I share or bookmark one specific test?
Yes. Each mode has its own hash, so /display-test/#black opens the black field and /display-test/#cycle opens the colour cycle. The field is drawn with CSS from that hash, which means the link still works with JavaScript disabled and still works offline once the page has been installed.
Why is my white field not pure white?
The page sends the value #ffffff, so anything else is being changed on the way to the panel. Check the operating system for night light or a blue-light filter, a colour profile, an HDR or adaptive-brightness mode, and any extension that applies a dark theme. Turn those off and the field will read as pure white.