How to use the screen test

Clean the screen and, for the dark patterns, dim the room.
Press Start the screen test. It opens full screen on the first pattern.
Click, tap or press → to go to the next pattern, and ← to go back. A short note at the bottom says what to look for; press Esc to stop.

To check one thing only, open that pattern from the list instead. The test works as a monitor test for desktop screens, laptops, TVs connected to a computer, and phones and tablets.

What each pattern shows

Black: lit pixels that should be dark, and, in a dark room, light leaking in at the edges and corners (backlight bleed) on LCD screens.
White: dark dots that never light up (dead pixels), and dust or marks on the screen.
Red, green and blue: pixels stuck on one colour, which show up as a dot of the wrong colour on at least one of them.
Grey: uniformity. It should be one even grey, without darker corners, clouds or bands.
Gradient: banding. Each ramp should run smoothly from black to full brightness, without visible steps.
Black level and White level: squares 1 to 16 steps away from pure black or white. The more you can tell apart, the better the screen shows shadow and highlight detail. Brightness and contrast settings change the result.
Sharpness: lines exactly one screen pixel wide, then two, then a checkerboard. They should look crisp and even. Grey mush or shimmering patterns mean the picture is being scaled: set the screen to its native resolution.
Colour bars: the standard colours, which should look clean and clearly separate.

Dead pixels, stuck pixels and bright dots

A dead pixel stays dark on every pattern. A stuck pixel is stuck on a colour, so it shows up as a coloured dot on some patterns and disappears on others. A bright dot on the black pattern is a pixel that stays lit.

Stuck pixels sometimes recover by themselves, and some people report success with rapidly flashing colours over the spot, but there is no reliable fix for a dead pixel. Most manufacturers have a pixel policy that says how many faulty pixels they accept before a repair or replacement, so check it, and the return period, soon after buying a screen.

About your screen

Above the patterns, the test shows what the browser reports about your screen. Screen is its resolution in physical pixels, worked out from the size the browser uses and the scaling the system applies. Browser zoom changes the scaling, so set the zoom to 100% for accurate numbers. Colour shows the colour depth, the widest colour range the screen supports (sRGB, Display P3 or Rec. 2020), and whether it is in HDR mode. Refresh rate is how many times a second the browser draws, which usually matches the screen; the refresh rate test measures it in detail.

More screen tools

White screen: a full-screen white light, warm or cool, for video calls, make-up or tracing.
Black screen: a plain black screen, for OLED screens, resting your eyes or checking for bright pixels.
Refresh rate test: your screen’s Hz, frame times and dropped frames.

Frequently asked questions

How do I test my monitor for dead pixels?

Start the screen test and look closely at the black, white, red, green and blue patterns. A dot that stays dark on all of them is a dead pixel; one that shows up in the wrong colour is stuck.

How do I check for backlight bleed?

Open the black pattern in a dark room, with the screen brightness at your usual level. Light glowing in from the edges or corners is backlight bleed. OLED screens do not have a backlight, so they do not bleed.

Can I test a TV, phone or tablet?

Yes. Open the page in the device’s browser, or show the computer’s screen on the TV, and step through the patterns full screen.

Why does the sharpness pattern look grey or shimmer?

Because the picture is being scaled: the screen is not at its native resolution, or the system or browser is zoomed. Lines one pixel wide only look crisp at the screen’s own resolution with no zoom.

Is the screen test free?

Yes. Every pattern is drawn in your browser: there is nothing to download or install.