What resolution is your screen really running?
Browsers report resolution in a way that confuses almost everyone, and a 4K TV often says 1920 x 1080. This test shows what your browser really draws at, explains what that does and does not tell you about the screen, and shows a fine pattern you can check by eye.
Your resolution
This test needs JavaScript to run. The explanation below still covers what the numbers mean, so the page is useful either way.
Reading your screen...
This takes a moment. We read the size your browser reports and multiply it by the pixel ratio to get the real number.
The numbers
Check the picture by eye
The numbers above are what the browser reports. This pattern is a check by eye: A one pixel checkerboard and fine line grid. If it looks like an even texture, nothing between the browser and the screen is blurring the picture. If it shimmers, moires badly or turns into a flat gray, the image is being scaled somewhere. An even texture does not prove 4K, because many 4K TVs draw web pages at Full HD and enlarge them to fill the screen.
Quick answer
The Screen Resolution Test shows the resolution your browser draws at, in physical pixels, and explains the number. On a computer or phone that is the screen itself. On a TV it often is not: Samsung's own developer guide says its 4K TVs run web content at 1920 x 1080 and use 4K for video, and on Android TVs we have measured browsers at 1280 x 720. So a 1080p reading on a 4K TV is normal and does not mean the screen is not 4K. The model number settles that.
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What this test can and cannot tell you
Resolution is one of the most misreported numbers on the web. Here is what is real.
Measured, but in CSS pixels. This is the coordinate space the browser lays out in. On TVs it is usually 1920 x 1080 or lower, whatever the screen is.
Calculated. Reported resolution multiplied by the pixel ratio. On a computer or phone this matches the screen. On a TV it is what the browser draws at, and many 4K TVs draw web pages at Full HD, so it can be lower than the screen.
Not from a web page on most TVs. When the browser draws at Full HD or lower, nothing on the page can see the 4K screen behind it. The model number or the settings menu settles it. On a computer monitor, the numbers and the pattern together do confirm it.
Not knowable. A browser sees pixels, never a diagonal measurement. Nothing on the web can tell you your screen size.
Different question. This measures the screen. What resolution Netflix is actually sending you depends on your plan, the title and your connection.
Why a 4K TV can say 1920 x 1080
CSS pixels are not panel pixels
Browsers work in a coordinate space designed so text stays a readable size on any screen. On a high density display, one CSS pixel covers several physical ones. The ratio between them is the device pixel ratio.
The arithmetic
Physical resolution equals reported resolution multiplied by pixel ratio. 1920 x 1080 at a ratio of 2 is 3840 x 2160, which is 4K. The test does this for you above.
Why TVs in particular do this
At three metres away, text drawn at true 4K density would be unreadably small, so TVs lay web pages out on a Full HD grid or smaller. Samsung's 4K TVs run web content at 1920 x 1080 and keep the full 4K resolution for video. That is normal behavior, not a fault, but it means the browser never sees the 4K screen.
What the number does tell you
A reading of 3840 x 2160 confirms a 4K screen. On a computer monitor or phone, a reading below its spec means a scaling setting is in the way. On a TV, a 1920 x 1080 reading on its own says nothing against 4K; the model number is the reliable answer.
Questions people ask
Why does my 4K TV report 1920 x 1080?
Because TVs lay web pages out on a Full HD grid so text stays readable from the sofa, and many draw them at that size too. Samsung's 4K TVs, for example, run web content at 1920 x 1080 and keep 4K for video, so the reading stays at 1920 x 1080 although the screen is 4K. On a TV, the model number is the reliable answer.
How do I know if my TV is really 4K?
Look up the model number, on the label on the back or in the settings menu: the spec sheet states the screen resolution. A reading of 3840 x 2160 here confirms 4K, but a 1920 x 1080 reading does not rule it out, because many 4K TVs draw web pages at Full HD. Our full guide, is my TV really 4K, covers the screen, the source and the cable.
Does this tell me what resolution Netflix is streaming?
No, that is a different question. This measures your screen. What a streaming service actually sends depends on your subscription tier, the specific title, your connection speed and the app. Our capability test and speed test cover that side.
My monitor reports a different resolution than Windows says.
Browsers report the CSS pixel space, and Windows display scaling changes that. At 150% scaling a 2560 wide monitor reports about 1707 CSS pixels. Multiply by the pixel ratio and you should get back to the real number.
Can you tell me my screen size in inches?
Not from the pixels, no. A browser is told about pixels, never about physical dimensions, so no resolution readout reveals inches. The one exception is indirect: some TV platforms send their model name to the browser, and a model name often contains the diagonal. Otherwise the size is on the box, the label on the back, or in the TV settings menu. Once you know it, our guide on how far to sit from your TV turns it into the right distance.
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