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Responsive preview tool

Responsive Website Tester

Preview a URL inside common viewport presets and custom sizes for quick responsive checks.

Open URL
Preview note Some websites block iframe previews using security headers.
Selected viewport 390 × 844
Target URL https://screenmetriclab.com

Preview ready

Load https://screenmetriclab.com at 390 × 844. If the preview stays blank, the target site may block iframe previews.

Open URL in new tab

Content cluster

Related guides

Use these supporting guides to understand the tool result and next testing steps.

QA workflow 6 min read

Responsive Testing Checklist

Use viewport size, DPR, breakpoints, orientation, and preview presets to reproduce responsive layout issues.

Read guide →
CSS units 6 min read

100vh vs 100dvh vs 100svh

Understand modern viewport height units and why mobile browser chrome can change visible page height.

Read guide →
Responsive design 5 min read

Tailwind and Bootstrap Breakpoints

Compare common framework breakpoints and learn why active breakpoints depend on viewport width, not monitor size.

Read guide →
View all guides →

Related tools

Continue with another ScreenMetricLab utility.

What Is My Screen Size?

Active

Check your live screen resolution, viewport size, DPR, browser, OS, orientation, color depth, and refresh rate.

Open screen checker →

Viewport Size Checker

Active

Measure the browser viewport and visual viewport that your website can use right now.

Check viewport →

Screen Resolution Checker

Active

Find the physical pixel grid reported by your current display and copy it for QA notes.

Check resolution →
View all related tools →