Viewport Tester
Test and monitor your browser viewport dimensions in real-time for responsive design.
📏 Responsive Breakpoints
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📱 Common Device Viewports
Understanding Viewport for Responsive Design
The viewport is the visible area of a web page in your browser window. It changes as you resize your browser and differs significantly between devices. Understanding viewport dimensions is crucial for responsive web design and ensuring your website works across all screen sizes.
This viewport tester updates in real-time as you resize your browser, showing the current dimensions and which responsive breakpoint applies. Use it to test your designs at various sizes without device emulators.
Viewport vs Screen Resolution
Screen resolution is your display's total pixels. Viewport is the browser's content area—it's smaller due to browser chrome, toolbars, and system UI. Web developers design for viewport, not screen resolution.
CSS Breakpoints Explained
Breakpoints are viewport widths where your layout changes. Common breakpoints: 576px (mobile), 768px (tablet), 992px (laptop), 1200px (desktop), 1400px (large screens). CSS frameworks like Bootstrap define these standard breakpoints.
Mobile-First Design
Mobile-first means designing for the smallest viewport first, then enhancing for larger screens using min-width media queries. This approach ensures essential content is always accessible while adding enhancements progressively.
Testing Responsive Layouts
Test your designs at multiple breakpoints, not just device sizes. Resize slowly to catch layout issues at "in-between" sizes. Browser DevTools offer device emulation for more thorough testing.
Viewport Meta Tag
The viewport meta tag controls how mobile browsers render pages. "width=device-width, initial-scale=1" ensures proper mobile scaling. Without it, mobile browsers render pages at desktop width and zoom out.