Does this tool update when I resize my browser window?

Yes, the viewport measurements update dynamically in real time as you drag and resize the window.

Updated: August 2026 • Verified v1.2

Screen Resolution & Viewport Checker

Internet & NetworkEssential

Check your physical screen resolution, CSS viewport dimensions, device pixel ratio (DPR), color depth, and orientation.

Local Browser Execution: Your input is processed locally in your browser and is not sent to UTL servers.

CSS Viewport Pixels = Physical Pixels / Device Pixel Ratio (DPR)

Understanding Your Results

Physical Screen Resolution is the raw hardware pixel count (e.g. 3840x2160). CSS Viewport is the logical layout area scaled by DPR (e.g. 1920x1080 at 2.0x DPR).

Practical Guidance & Next Steps

Drag your browser window edges to observe CSS viewport values update in real time. Use these dimensions to test CSS `@media (min-width: ...)` query breakpoints.

What is this?

A real-time display inspection tool that shows physical monitor pixels versus CSS logical viewport pixels and updates live as you resize your window.

How does it work?

Monitors `window.screen` and `window.innerWidth/innerHeight` with resize listeners to display dimensions, aspect ratios, and pixel densities.

Why use it?

Critical for responsive web design testing, validating Retina / High-DPI scaling, and ensuring CSS media queries trigger at correct breakpoints.

Technical Scope & Calculation Limitations

Browser security sandboxes do not expose multi-monitor coordinate arrangements beyond the window's current active screen.

Frequently Asked Questions

High-density displays (like Apple Retina or 4K monitors with 125%-200% scaling) use multiple physical pixels to render one CSS pixel for crisp text rendering (DPR > 1.0).

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