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Screen Resolution & Viewport Tester
Live window dimensions and aspect ratio.
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About Screen Resolution & Viewport Tester
Display live window, screen, and viewport dimensions plus common breakpoint status.
📐 Methodology & Reference Accuracy:
Calculations, formulas, and conversions execute locally in your web browser. Output models are benchmarked against official reference standards and updated for 2026.
🔒 This tool runs entirely in your browser. Nothing is uploaded or stored.
Background reading: Viewport Tester on Wikipedia. More: all developer tools.
Frequently Asked Questions about Screen Resolution & Viewport Tester
How do I use the Screen Resolution & Viewport Tester?
Open the Screen Resolution & Viewport Tester and use the controls in the workspace below: live window dimensions and aspect ratio. Results appear instantly in your browser, with nothing to install, sign up for, or pay for.
Is the Screen Resolution & Viewport Tester free?
Yes. The Screen Resolution & Viewport Tester is completely free, like every tool in the PrimeFreeTools library. There are no accounts, subscriptions, or usage limits.
Does the Screen Resolution & Viewport Tester store or share my data?
No. The Screen Resolution & Viewport Tester runs with JavaScript in your browser, so what you enter never leaves your device and nothing is stored on a server.
What can I use the Screen Resolution & Viewport Tester for?
Display live window, screen, and viewport dimensions plus common breakpoint status. You will find it grouped under Developer Tools together with 78 other free tools on the PrimeFreeTools homepage.
Related Articles & Guides
Sep 9, 2026
Viewport Tester: Why ‘It Looks Fine on My Screen’ Kills Layouts
Live window dimensions and aspect ratio.
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