Screen resolution
Measuring…
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Live browser diagnostic
Viewport Size Checker
Measure the browser viewport and visual viewport that your website can use right now.
Current viewport size
Measuring…
The CSS width and height your website can use right now.
Updates live
Resize the browser and this value changes.
CSS-focused
Useful for breakpoints and layout tests.
Includes visual viewport
Helpful on mobile browser chrome changes.
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Full diagnostics
Detailed browser, display, viewport, DPR, OS, orientation, color depth, and refresh-rate values.
Current viewport
Measuring…
This is the CSS viewport your website sees.
Device pixel ratio
Measuring…
Visual viewport
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Browser
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Operating system
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Orientation
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Color depth
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Refresh rate
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Zoom/scaling note: Checking…
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How to use this result
The viewport value is the browser area available to CSS and JavaScript. It changes when users resize the window, change zoom, rotate a mobile device, use responsive mode, or open split-screen mode.
Use this result when debugging responsive breakpoints, sticky headers, mobile browser chrome, and visual viewport behavior. Viewport height can also change because of browser UI and screenshot tools.
Privacy note
This MVP checker runs in your browser. It does not require signup, file uploads, or personal account data to show your screen metrics.
MVP checker guide
How to use viewport size
Viewport size is the browser area available to CSS and JavaScript. It is often the most important number when debugging responsive layouts.
Breakpoint testing
Compare your current viewport width with CSS breakpoints to confirm which layout should be active.
Viewport height changes
Viewport height can change because of browser UI, zoom, screenshot tools, responsive mode, mobile address bars, or split-screen layouts.
Mobile browser behavior
On phones, browser chrome and address bars can change the visual viewport, especially while scrolling or focusing inputs.
QA reproduction
Copy viewport dimensions with browser and OS details to help teams reproduce layout issues.
Frequently asked questions
What is viewport size?
Viewport size is the width and height of the browser area available for displaying a webpage.
Why is viewport size different from screen resolution?
Browser UI, zoom, OS scaling, and device pixel ratio can make the viewport smaller than the physical screen resolution.
Does viewport size update automatically?
Yes. This page updates when the window is resized, orientation changes, zoom changes, screenshot/responsive tools change the page area, or visual viewport changes are detected.
Should developers use viewport or screen resolution?
For CSS layouts and breakpoints, viewport size is usually more important than physical screen resolution.
Content cluster
Related guides
Use these supporting guides to understand the tool result and next testing steps.
Related tools
Continue with another ScreenMetricLab utility.