Browser Window Size Checker
Measure live viewport dimensions, breakpoint class, and device pixel ratio while testing responsive layouts.
Viewport width
0px
Viewport height
0px
Device pixel ratio
1.00
Active breakpoint
Mobile
Why Frontend Teams Use This Tool
Real-time viewport tracking
Watch width and height change live as you resize your browser.
Breakpoint labeling
Map the viewport to a practical device class instantly.
DPR visibility
See device pixel ratio while debugging responsive rendering issues.
Frequently Asked Questions
What is the difference between screen size and browser window size?
Screen size is the full device display resolution. Browser window size is the current visible viewport inside the browser, which is what responsive layouts actually respond to.
Why check device pixel ratio?
DPR affects image sharpness, canvas rendering, and some media query behavior on high-density displays.
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