Dead Pixel Test
Fill the screen with five solid colors to spot dead, stuck and hot pixels.
Screen Cleaner: Black Screen and Touch Lock
This page cleans nothing: it fills your screen with black to show dust or white to show smudges, and ignores taps on the page. Find the marks before you turn the device off to clean it, then check again afterward.
Turn the device off before you clean it
Makers such as Apple, Samsung and LG say to turn a device off or unplug it before cleaning, so find the marks here first and check again afterward. If you dust with the screen on, use only a dry cloth, and never spray liquid onto it.
Showing Black
Black shows dust and lint.
Runs entirely in your browser. Test results, audio and video never leave your device.
How to see dust and smudges on your screen
- Under Field, choose Black to see dust and lint, or White to see smudges and streaks. Under Lock for, choose 30 s, 1 min or 2 min.
- Press Start cleaning, or click or tap the preview. The field fills the screen, and the page ignores taps and clicks; the keyboard works as usual.
- Note where the dust and smudges are. If you give the screen a quick dry dust-off now, the line under Hold to unlock counts the touches the page ignored.
- To unlock early, press and hold Hold to unlock for 2 seconds, or hold Space or Enter: the button has focus from the start. One press of Esc also unlocks, and so does the countdown reaching 0:00.
- For a full clean, turn the device off or unplug it first, as its maker advises. Then turn it back on and press Start cleaning again to check the result.
What does an online screen cleaner do?
An online screen cleaner cleans nothing: it fills the screen with black to show dust or white to show smudges, so you can find marks before you turn the device off to clean it, and check afterward. It also ignores taps on the page, in case you give the screen a quick dry dust-off while it is on. System gestures, hardware buttons and the keyboard still work.
How to clean a screen without damaging it
Apple, Samsung and LG say to turn a device off or unplug it before cleaning. The touch lock is only for a quick dry dust-off, if you do one with the screen on. For a laptop cleaning mode that also ignores the keyboard, use the Keyboard Cleaner.
- Find dust on the Black field, and fingerprints and streaks on the White field.
- Turn the device off or unplug it, as its maker advises.
- Wipe gently with a soft, dry, lint-free cloth, such as microfiber.
- For marks that stay, follow the maker's instructions with the device still off; some allow a slightly damp cloth. Never spray anything onto the screen.
- Avoid abrasive cloths, compressed air, bleach, window cleaner and solvents, which makers warn against.
- Let the screen dry, turn the device back on, and check the result on both fields.
What the lock can and cannot block
The page can ignore input aimed at it. The system and the browser handle some input before any page sees it, so that input still works.
| Input | While the lock is on |
|---|---|
| Taps, clicks and pen presses on the field | Ignored and counted |
| Scrolling, zooming and long-press menus on the page | Ignored |
| Pull-to-refresh and the browser's swipe navigation | Blocked in Chrome, Edge and Firefox. Safari ignores the block. |
| The keyboard | Works as usual. One press of Esc unlocks and leaves fullscreen. |
| System gestures, such as edge swipes, the notification shade, the home swipe and Reachability | Not blocked |
| Gestures that work anywhere on the screen, such as Windows 11 three- and four-finger swipes, iPad multi-finger gestures, Zoom on iPhone and iPad, and magnification on Android | Not blocked. Windows 11 can turn its three- and four-finger gestures off under Settings > Bluetooth & devices > Touch. |
| Power, volume and brightness buttons | Not blocked |
What the fields show
- On Black: dust, lint and hairs, which catch the light and stand out as pale specks.
- On White: fingerprints, smudges and streaks, which show as hazy or uneven patches.
- Marks still there after cleaning: dirt stuck to the glass, a scratch or a faulty pixel. The Dead Pixel Test tells a pixel fault from dirt.
- Faint bands or blotches that stay after cleaning, which may be in the panel itself. The Screen Uniformity Test shows them on gray.
- Specks that seem to sit behind the glass, which can be dust inside the panel that no cloth can reach.
- How many touches the page ignored, shown under Hold to unlock while the lock is on.
How it works
Start cleaning paints the screen #000000 for Black or #ffffff for White, through the Fullscreen API where the browser has it. While locked, the page cancels touch, pointer, mouse, wheel and context-menu events on the field, counting each finger, pen or mouse press as one touch, and leaves keys alone. Only Hold to unlock responds to touch, after 2 seconds of holding.
The countdown runs only while the page is visible. CSS touch-action and overscroll-behavior hold back panning and pull-to-refresh, and the Screen Wake Lock API keeps the screen on where supported.
Limitations
- The page cleans nothing. Makers say to turn a device off or unplug it before cleaning, so never use a damp cloth while the screen is on, and never spray liquid onto it.
- Your device still receives every touch; the page only ignores them. Gestures the system or the browser handles first still work, and a wipe with several fingers or the side of a hand can set them off.
- On iPhone, the browser does not let a page go fullscreen, so the field covers only the browser window, and the browser's own toolbar still responds to taps. On iPad, Safari's fullscreen shows an overlay button the page cannot hide, and a wipe can press it.
- Each lock lasts 2 min at most, so the page never stays locked for someone who cannot press and hold. Press Start cleaning again to keep going.
- On an OLED screen, do not leave the White field on for hours.
Frequently asked questions
Is it safe to clean a screen while it is on?
No, not by the makers' instructions: Apple, Samsung and LG say to turn a device off or unplug it before cleaning it. Find the marks on the fields first, clean with the screen off, then turn it back on and check. If you dust it while it is on, use only a dry cloth.
Why can I still open the notification shade while the screen is locked?
Because the phone or tablet handles that swipe before the browser sees it. The page can ignore taps and swipes on its own content, but edge swipes, the notification shade, the home swipe and hardware buttons belong to the system.
Can I lock the whole touch screen on an iPhone or iPad?
Yes, with Apple's Guided Access rather than a web page. You turn it on in Accessibility settings, and during a session with Touch turned off, the screen ignores every touch. Ending a session needs the Guided Access passcode, Face ID or Touch ID.
Does the Screen Cleaner lock the keyboard?
No. The keyboard works as usual, so keys you press still reach the page and the browser, and one press of Esc unlocks. To have key presses ignored while you clean a keyboard, use the Keyboard Cleaner. To check the keys afterward, use the Keyboard Test.
Can the lock last longer than 2 minutes?
No. Each lock lasts 30 s, 1 min or 2 min, so the page unlocks by itself for anyone who cannot press and hold, such as a screen reader user in browse mode. Press Start cleaning again for another round.