Your screen dimensions, browser viewport, device pixel ratio, and aspect ratio, detected instantly.
This tool reads browser screen and viewport data immediately. Resize the browser later to compare viewport changes.
Reading your screen information
Reading your screen information
Detecting screen profile
Reading your screen information
This page is built for the simple question first: what is my screen size? For most users, the immediate answer is the pixel resolution shown at the top, such as 1920 × 1080. That tells you how many pixels the screen can display horizontally and vertically. But screen size tools are often confusing because people use the same phrase to mean different things. Sometimes they mean resolution, sometimes viewport size, and sometimes the advertised physical diagonal in inches. This tool starts with what the browser can detect instantly, then adds the surrounding context so the numbers make sense. If you only need a quick screen size checker for support, setup, or responsive debugging, the main resolution and viewport blocks are usually enough. If you need deeper context, the rest of the page explains why the values may not match what your laptop or monitor box says.
Screen resolution and viewport size are related but not identical. Screen resolution is a hardware-level display property exposed by the browser through the screen API. Viewport size is the actual browser content area available to a webpage right now. That means your screen resolution can stay at 2560 × 1440 while your browser viewport is only 1280 × 720 because the window is smaller, split, docked, or affected by interface chrome. This distinction matters for web design, responsive testing, and support diagnostics. When someone searches for what is my screen resolution, they often want the physical display dimensions. When someone searches for my viewport or browser window size, they usually care about layout behavior inside the browser. A good screen resolution detector should show both, side by side, without pretending they mean the same thing. That is why this page updates viewport size live when the window changes while keeping the hardware screen dimensions stable.
Device pixel ratio, often shortened to DPR, explains why a screen can look extremely sharp without reporting a huge CSS viewport. A DPR of 2 means one CSS pixel maps to two physical pixels in each direction. That is common on Retina-style displays and other dense panels. So your browser may render a layout at 1440 × 900 CSS pixels while the real physical pixel grid is much higher. This is one reason people get confused when asking what is my screen resolution or why the browser reports a smaller width than expected. Device pixel ratio sits in the middle between the physical panel and the CSS layout space the browser uses for design. If you build interfaces, test breakpoints, or debug screenshots, DPR matters a lot. If you are just checking a monitor resolution, it matters less, but it still explains why the same web page can look sharper on one device than another.
For web design, the most useful number is often the viewport, not the full hardware resolution. A responsive layout reacts to the browser’s available content area, so a screen size detector for design work should always expose both values. If your monitor is wide but your browser is snapped to half the screen, your effective layout width is much smaller than the monitor resolution suggests. This is why designers, front-end developers, and QA testers care about browser viewport size, browser window size, DPR, and zoom context. A practical workflow is simple. First check the hardware resolution to understand the device. Then watch the live viewport block while resizing the browser to see how the layout space changes. Finally use the DPR and aspect ratio values if you are comparing screenshots, high-density displays, or image sharpness.
The most common desktop and laptop resolutions still cluster around a few familiar classes. Full HD at 1920 × 1080 remains the mainstream baseline. QHD at 2560 × 1440 is common on sharper monitors and gaming displays. 4K at 3840 × 2160 is widely recognized but still not universal. Laptop screens often introduce slightly different ratios such as 2560 × 1600 or 2880 × 1800, which trade traditional 16:9 for taller formats. Tablets and phones bring even more variation, especially when high DPR compresses the browser viewport into a smaller CSS space. That is why a modern what is my screen size tool should not reduce everything to one label. The resolution alone is useful, but the aspect ratio, viewport size, and DPR help explain what kind of screen experience you are actually looking at.
There are several normal reasons for this. The advertised screen size on a laptop or monitor box usually refers to diagonal inches, not pixel resolution. The browser, however, can only detect pixel-based properties and related metrics like DPR, color depth, and viewport dimensions. Operating-system scaling also changes how large things appear without changing the underlying panel. Browser zoom adds another layer by affecting the effective viewport. On high-density displays, the CSS space can look much smaller than the physical pixel matrix would suggest. This is why users often say my screen resolution looks wrong when the browser is actually reporting something valid from its own perspective. The page is honest about that limit. It can detect the browser-visible technical values immediately, but it cannot magically know the manufacturer’s marketed inch size without outside information.
In browser terms, this usually means your screen resolution in pixels, such as 1920 × 1080, plus the current viewport size available to the page.
Screen resolution is the full display dimension reported by the device. Viewport size is the actual browser content area available to the webpage right now.
Because viewport size reflects the live content area of the browser window, not the fixed hardware resolution of the display.
Device pixel ratio shows how many physical pixels are used for each CSS pixel. High-density displays often use values like 2.0 or higher.
Not exactly. It can only estimate based on assumptions or related metrics. Exact physical size requires your real panel diagonal or PPI.
Because CSS viewport width, operating-system scaling, browser chrome, and device pixel ratio can all make the reported browser size smaller than the physical display resolution.
It is both. The page is designed to capture screen-size and screen-resolution intent while also showing live viewport data for practical browser use.
Yes. The live viewport block is useful for checking how the browser content area changes while resizing the window.
Zoom can affect the effective browser layout space and how some values feel in practice, even when the hardware resolution stays the same.
Use the PPI Calculator when you know the screen diagonal and need a more exact pixel-density calculation.