Viewport Size Checker
Open the tool at the browser size you want to test to see the live layout viewport width, height, and related display values.
Viewport CSS width and height, screen dimensions, available screen area, and device pixel ratio will appear here.
How to Use Viewport Size Checker
- Resize the browser window or rotate the device to the target layout.
- Read the viewport width and height in CSS pixels and note device pixel ratio separately.
- Test responsive breakpoints by content behavior instead of assuming that one viewport value represents every device.
Viewport Size Versus Screen Resolution
The layout viewport is the CSS-pixel area available to the page. It can differ from physical screen pixels because of browser chrome, zoom, operating-system scaling, device pixel ratio, keyboards, and dynamic mobile toolbars.
Use viewport measurements for responsive layout diagnosis, not hardware identification. Modern devices share many CSS viewport sizes, and accessibility settings can materially change the available area.
Viewport Size Checker Example
A laptop panel may have 2560 by 1600 physical pixels while a scaled browser reports a viewport near 1280 CSS pixels wide. The page lays out against the CSS measurement.
Frequently Asked Questions About Viewport Size Checker
Why is the viewport smaller than the screen resolution?
Browser controls, window size, zoom, operating-system scaling, and device pixel ratio reduce or transform the CSS layout area.
Does device pixel ratio equal browser zoom?
Not exactly. Device pixel ratio relates CSS pixels to device pixels and can also be affected by display scaling and browser zoom.
Should responsive breakpoints target specific devices?
Content-based breakpoints are more durable because devices, window sizes, split-screen modes, and zoom levels vary.