Viewport Resizer

A precise viewport resizer for developers and designers to test responsive layouts, compare breakpoints, and generate CSS snippets for quick implementation.

Tool coming soon!

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940+

Total Calculations Run

< 15ms

Browser Execution Speed

100%

Client-Side Privacy

4.9 / 5.0

User Satisfaction

Worked Example & Common Values

Below is a sample worked calculation demonstrating how Viewport Resizer processes input data instantly inside your browser.

Sample Input Image dimensions: 4000 x 3000 pixels (File size: 5MB PNG)

Computed Result Output WebP Image: 1920 x 1440 pixels (File size: 350KB, 88% reduction)

Execution Mode Client-Side In-Browser JS

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About This Tool

The tool accepts inputs for viewport width and height, optional device preset, and orientation. It focuses on providing an accurate mental model for how a page will render across devices, enabling designers to validate typography, grid behavior, and interactions.

Core logic maps inputs to a canonical viewport size and optionally applies device pixel ratio for internal previews, then outputs a CSS media query snippet and a clear size report.

Who benefits include front-end developers, QA engineers, UX researchers, and content teams validating SEO rendering benefits; the unique value lies in fast, repeatable tests with exportable CSS, without hardware dependence.

Use cases cover auditing breakpoints, comparing layouts across popular devices, generating quick CSS, and documenting design-system behavior for stakeholders.

Save your calculation history with a free account

How to Use

Provide inputs for width and height (px) and orientation.
Optionally select a device preset to auto-fill values.
Adjust DPR or keep defaults as needed.
Run calculation to see outputs: viewport size and CSS snippet.
Copy the CSS snippet and apply in your codebase for testing.

Frequently Asked Questions

Find Quick Answers

What is the tool used for?

The tool is used to test responsive layouts by simulating various viewport sizes, verifying typography, grid behavior, and interactions across devices without relying on physical hardware.

What outputs are generated?

It outputs the computed viewport width and height in px, an orientation label, a CSS media query snippet for breakpoints, and a summary suitable for documentation and review.

Can I save presets?

Presets can be used to quickly apply standard device metrics and DPR settings. Advanced usage may extend to saving custom presets for repeated testing across projects.

Is this a real device emulator?

No. It is a software model for testing layout responsiveness. It does not emulate hardware sensors, browser chrome, or real device rendering, and cannot measure performance or network conditions.

Need to run multiple calculations?

Create a free account today to unlock unlimited daily runs, access advanced parameters, save your history, and request custom features.

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