DeviceBenchFree full-screen black
Black screen with nothing drawn on it
One click drops a #000000 field over the whole display and takes the cursor, the tab strip and the taskbar with it; three seconds later the exit button fades too, so the glass is showing black and only black. On an OLED that means the pixels under the field are switched off rather than dimmed, which is why the panel measurably stops drawing power for that area. On an LCD the backlight behind the crystal stays lit whatever the image says, so the screen goes dark and the power draw does not move — the same field, two very different pieces of hardware.
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- #000000
- Cursor hidden
- Display held awake
This browser has no Wake Lock API — Firefox is the usual one — so the display still sleeps on its own timer.
This browser will not hand a page the whole display, which on an iPhone or iPad is a rule rather than a setting. The field still covers everything the page is allowed to cover; the address bar and the tab strip stay lit, so drag them out of the way before you judge how dark the panel goes.
Two monitors? Drag this window onto the one you want dark before you press the button — a projector or a television plugged in as a second display counts the same way.
How to blank a screen with this field
Three moves, and the second one is the reason the controls disappear on their own.
Move this window onto the screen you want dark
Full screen follows the window, not the mouse, so the display holding this tab is the display that goes black. On a two-monitor desk that is the whole trick: drag the tab across, drop it, and leave the pointer wherever you like. Nothing else on that screen has to be closed or moved first.
Press Go black, then take your hands off the desk
The field opens immediately and the exit button and the pointer both disappear after three seconds of stillness. That gap exists so you can start it and then pick up a cloth: from then on the glass is showing #000000 with no lit pixel anywhere to distract you from a smear. Any mouse movement brings the button back for another three seconds.
Leave with Escape, or with the button that reappears
Escape always works and no page is allowed to take it from you, which is why it is worth knowing before you cover the screen. Clicking or tapping the field itself deliberately does nothing — wiping a monitor is a stream of accidental clicks, and a field that exits on the first one would be useless for the job most people open it for.
Technical specifications
| Field color | #000000 — sRGB 0, 0, 0, flat across the panel, with no logo, gradient or watermark drawn on it |
|---|---|
| Controls fade after | 3 seconds without a mouse move, touch or key press; the pointer is hidden with them |
| Taps on the field | Ignored by design, so a cloth dragged across the glass cannot close it |
| Ways out | Escape at any time, or the Exit button that returns on the first movement |
| Display sleep | Held off through the Screen Wake Lock API; unsupported in Firefox and reported as such rather than assumed |
| What a black LCD still emits | About 1/1000 of its white output on a typical IPS panel — near 0.3 cd/m² at a 300 cd/m² setting |
| iOS and iPadOS | No page may go full screen, so the browser's own bars stay visible above the field |
| State kept | None — the field is one element with a background color, and closing the tab is all the cleanup there is |
Frequently asked questions
How do I blank one monitor and keep working on the other?
Drag this tab onto the monitor you want dark and start the field there. The operating system still counts that display as connected and awake, so your window layout on the other screens is untouched — which is the practical difference between this and switching the display off. Turn a monitor off in Windows display settings and every window living on it is evicted onto the remaining screens, then does not come back where it was.
Is it safe to clean the screen while it is showing black?
It is the right field for finding smears, but clean a screen that is cool rather than one that has been on for hours. Use a dry microfiber cloth first, and if you need liquid, put it on the cloth and never on the glass — spray runs down into the bezel and the panel's edge is the one place a monitor cannot dry out. Avoid anything with ammonia or a high alcohol content on a matte anti-glare coating, which is a thin film rather than part of the glass and clouds permanently once it is stripped.
Does a black screen really save battery?
On an OLED panel yes, on an LCD no, and the gap is large enough to matter. Every OLED pixel makes its own light, so a pixel set to 0,0,0 is simply off — Google's own measurement of a dark interface on an OLED phone at full brightness came out around 40% lower in total device power than the white version of the same screen. An LCD has one backlight behind the entire panel that stays at whatever brightness you set it to; the crystals block the light rather than the panel switching it off, so a black LCD costs almost exactly what a white one costs.
The field looks dark gray rather than black. Is my monitor faulty?
That is normal on an LCD and it is a specification rather than a fault. A typical IPS monitor has a contrast ratio near 1000:1, meaning its black is one thousandth of its white — at 300 cd/m² that leaves roughly 0.3 cd/m² still coming out of a black screen, which your eyes find easily in a dark room. VA panels reach 3000:1 or better and look visibly darker; OLED switches the pixel off and has nothing to leak. If the gray is uneven rather than flat, that is a different question, and the backlight bleed test is the page that answers it.
Why does my display still dim or lock while the field is open?
Because a browser can ask for the screen to stay awake but cannot overrule the machine. The Screen Wake Lock API is what this page uses, and the status line under the button tells you whether it was granted, refused or missing altogether — Firefox has no implementation at all. Even when it is granted, a corporate lock-screen policy, a laptop closing its lid and some power profiles still win, because they run below the browser.
Can a black image burn into a screen?
No, and on OLED it is the opposite of the problem. Burn-in comes from pixels that have been driven bright for a long time — a taskbar, a channel logo, a heads-up display — aging faster than their neighbors; a pixel showing black is the one that is resting. What can happen on any panel is temporary image retention, where a faint ghost of the last thing on screen lingers for a minute against the black. If yours is still there after a few minutes, that is the case the burn-in page is built to check.
Does this work on a phone or tablet?
It works everywhere, but Safari on iPhone and iPad never lets a page take over the display, so the address bar and the status bar stay lit above the field. Everything else — the wake lock, the fading controls, the ignored taps — behaves the same. On Android, Chrome grants the whole screen and the field really does become the entire panel.
About black on an LCD, an OLED and a projector
Black is the one color a display cannot simply produce, and how close it gets is the single number that separates panel technologies. An LCD works by putting a shutter in front of a lamp that never turns off: the liquid crystal twists to block the backlight, and how much still escapes is the contrast ratio printed on the box. A typical IPS monitor sits near 1000:1, so its black is a thousandth of its white; a VA panel reaches 3000:1 to 6000:1 and looks properly dark by comparison; an OLED has no lamp behind it at all, switches the pixel off, and emits nothing measurable. That is why the same field looks like charcoal on an office monitor, like ink on a television, and like a hole in the desk on a phone.
Most people do not open a black field to look at a panel. They open it to make a screen stop existing for a while, and the three common versions of that are worth naming. A second monitor during a call or a presentation, where the point is that the display stays connected — the moment you switch it off in the operating system, every window living on it is thrown onto the remaining screens and does not return to its place. Cleaning, where a lit screen hides exactly the film you are trying to remove and a dark one shows every finger mark at a glance. And a projector or a television between segments, where cutting to black is faster and quieter than shuffling sources. None of those is a diagnostic; they are a screen being used as a piece of furniture, which is why this page has one button and no test patterns. If you do want to spend a minute on the panel while it is dark, a bright dot on a black field is a stuck pixel, and the dead pixel checker walks all five fields that tell the pixel faults apart.
Two things people blame on a black screen belong to other pages. Light that pools in the corners or runs in a bar along one edge is not the panel failing to reach black, it is the backlight escaping around the frame that clamps the panel, and it is judged against gray steps as well as black on the backlight bleed test. A faint ghost of a taskbar or a browser window that survives on the black field is image retention, which fades, or burn-in, which does not, and telling those two apart needs the timed wash on the burn-in test. If you would rather go through everything a display can be wrong about in one sitting — geometry, sharpness, grayscale steps, solid fills — the monitor test runs the whole sequence and records a verdict for each pattern, and the white screen is the same idea as this page at the other end of the scale.
What this page knows about your screen
Every number on this page is worked out by JavaScript running in the tab you are reading it in. Nothing you type, paste or open is uploaded, logged or kept, which is also why the tools carry on working after you disconnect from the network.
The field has no state to keep: it is a single element with a background color, two checkboxes that live in the tab’s memory until you reload, and a wake-lock request the browser grants or refuses. Nothing about your display is read, and nothing about what you covered up is recorded.