WebToolsPlanet
Developer Tools

Responsive Website Tester

Check how a website behaves across common responsive viewport sizes.

Last updated: May 29, 2026

Client-Side Processing
Input Data Stays on Device
Instant Local Execution

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What is Responsive Website Tester?

Responsive Website Tester embeds a URL inside a resizable preview frame with common phone, tablet, laptop, and desktop dimensions. It helps catch layout overflow, breakpoint mistakes, and content crowding while staying in one browser tab.

How to Use Responsive Website Tester

1

Enter a website URL.

2

Choose a viewport preset or enter a custom width and height.

3

Rotate the viewport when needed.

4

Use the scaled preview to inspect the page.

Common Use Cases

  • Checking responsive breakpoints before publishing a page.
  • Reviewing mobile layouts from a desktop browser.
  • Comparing tablet and desktop hero sections.
  • Testing custom viewport dimensions from design QA.

Example Input and Output

Preview a homepage at a phone viewport.

URL and viewport
https://webtoolsplanet.com at 393x852
Preview
Phone-sized iframe preview

Iframe limitation

Use this for quick layout inspection. For final QA, also test in real browsers and devices.

Frequently Asked Questions

Why does a website show a blank preview?
Some sites block iframe embedding with X-Frame-Options or Content-Security-Policy headers. Open the URL in a new tab to inspect those sites.
Does this emulate a real device?
It changes viewport size, but it does not fully emulate browser engines, network conditions, or device hardware.
Are URLs uploaded to WebToolsPlanet?
No. The preview is created in your browser with a normal iframe.

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