What a black screen is used for
- Checking backlight bleed and IPS glow around the edges of an LCD
- Finding stuck pixels, which show as bright dots against black
- Saving power on an OLED or AMOLED display, where black pixels are switched off entirely
- Blanking a screen during a presentation without shutting anything down
- Cleaning a monitor — dust and streaks are far easier to see on black
Black screen online: #000000 at full screen
Black is where the two main panel technologies visibly part ways. On an OLED, a black pixel is simply off, so the screen goes genuinely dark and draws almost no power. On an LCD the backlight is still on behind the shutter, so what you get is very dark grey, and any unevenness in that backlight becomes obvious.
That unevenness is what people mean by backlight bleed and IPS glow. Bleed is brighter patches, usually along one edge or in a corner, where light escapes past the panel. Glow is a broader silvery haze that shifts as you move your head. A small amount of both is normal on IPS; large bright patches are not.
Look at a black screen in a dark room, not a lit one. Ambient light washes out exactly the faults you are trying to see, and a screen that looks perfectly black at midday can be visibly blotchy at night.
How to get a full screen black background
Press the fullscreen button on the player above, or the F key. Escape returns you to the page. On a desktop browser F11 does the same job and hides the browser's own toolbars as well.
The colour box is a control, not a picture: use the hex field to enter any value, pick another shade from the palette, or download the current colour as a PNG at your screen's resolution. Whatever you set is written into the address bar, so the link you copy reproduces exactly what you are looking at.