Responsive Website Checker

Preview any website across popular device sizes — mobile, tablet, and desktop — all in your browser.

Viewport: 1280px × 800px

Enter a URL above to preview

Type a website address and click Preview

About This Tool

The Responsive Website Checker lets you instantly preview how a website renders at various screen sizes — from small smartphones to large desktop monitors. Select from popular device presets or enter a custom viewport size to test your breakpoints and layout.

Why Some Sites Don't Load

Many websites set X-Frame-Options: DENY or a strict Content-Security-Policy to prevent embedding in iframes. This is a security feature and cannot be bypassed. Use your browser's built-in DevTools (F12 → Device Toolbar) to preview those sites.

How to Use

  1. Enter a URL in the input box (with or without https://).
  2. Click Preview to load the site in the frame.
  3. Select a device preset or switch orientation to test different viewports.
  4. Use Custom to set any exact pixel width and height.

Common Use Cases

  • Quickly verify mobile layout without opening DevTools
  • Check a client's live site on tablet breakpoints
  • Compare portrait vs landscape rendering on phones
  • Spot overflow or clipping issues at specific widths
  • Test third-party or staging URLs that you don't own locally

Frequently Asked Questions

Why does the preview show a blank page?

The target site has likely set headers that block iframe embedding. This is a security restriction imposed by the external website, not this tool.

Does this tool work for localhost?

No, because this page is served over HTTPS and cannot load http://localhost URLs due to mixed-content restrictions. Use browser DevTools for local development.

Is my URL sent to any server?

No. The URL is loaded directly in your browser's iframe — no data passes through our servers. Everything runs client-side.

What is responsive web design?

Responsive web design is a development approach where a website's layout adapts to the screen size using flexible grids, CSS media queries, and fluid images so content looks great on any device.