Screen resolution test

Your real resolution, aspect ratio, pixel ratio and colour depth, read from your own browser.

Escape or one tap comes back.

Every colour, one tap away

Brightness, timer and colour cycle

What the readout tells you

The test reports five things. The physical resolution of the display in real pixels. The aspect ratio, reduced honestly. The size of the browser window in CSS pixels, which is what a web page is laid out against. The device pixel ratio, which is how many real pixels the system is packing into each CSS pixel. And the colour depth in bits.

The gap between the first and third numbers is usually the interesting part. If your display is 3840 by 2160 but the browser window reports around 1920 by 1080, your system is running at 200 percent scaling, which is correct and deliberate on a 4K laptop panel. Text is being drawn with four times the detail in the same apparent size.

About that aspect ratio

This test reports the real ratio rather than the marketing one. A 3440 by 1440 ultrawide is sold as 21:9 and is actually 43:18. A 2560 by 1080 ultrawide is sold as 21:9 and is actually 64:27. Neither is within rounding distance of 21 to 9, so calling them that would be repeating a marketing name rather than measuring anything. Where a resolution has a recognised name, such as Full HD or UWQHD, the test gives you that alongside the arithmetic.

Checking a display is what the listing said

  • Run this on a secondhand monitor or laptop before you buy. A panel advertised as 1440p that reports 1080 is the fastest possible way to end a negotiation.
  • Check the pixel ratio on a phone. Manufacturers quote the physical resolution, and the browser reports what is really being driven.
  • A colour depth of 24 bit is normal and means eight bits per channel. Some systems report 30 bit on a genuine 10 bit panel with the right cable and settings.
  • If the numbers change when you move the window between monitors, that is correct: you are reading whichever display the window is on.

Scaling, sharpness and why text looks soft

If text looks soft on an external monitor, check whether the system is running the panel at something other than its native resolution. An LCD has a fixed grid of pixels and can only be truly sharp at that grid. Anything else has to be interpolated, and interpolation is why a 1440p monitor fed 1080p looks worse than a 1080p monitor does. The fix is to set the native resolution and adjust the scaling percentage instead, which keeps the grid intact and changes only the apparent size.

Frequently asked questions

What is my screen resolution?

Press the button and the test reports it directly, along with the aspect ratio, the browser window size in CSS pixels, the device pixel ratio and the colour depth. All of it is read from your own browser and none of it leaves your machine.

Why does the browser window size differ from my screen resolution?

Because the system is scaling. A 3840 by 2160 display running at 200 percent scaling reports roughly 1920 by 1080 of layout space, and text is drawn with four times the detail at the same apparent size. That is correct behaviour on a high density panel.

Why does my ultrawide say 43:18 instead of 21:9?

Because 3440 by 1440 really is 43:18. So is 2560 by 1080, which is 64:27. Neither is within rounding distance of 21 to 9, which is a marketing name rather than an arithmetic one. The test gives the recognised name alongside the real ratio.

Why does text look soft on my external monitor?

Usually because the system is running the panel at something other than its native resolution, and an LCD can only be truly sharp at its own pixel grid. Set the native resolution and change the scaling percentage instead.