Preview any URL at mobile, tablet, and desktop breakpoints to test how your site responds to different screen sizes.
This tool renders any URL inside an iframe sized to a specific viewport width, simulating how a browser displays the page on that device. Use it to quickly check that your responsive breakpoints behave as expected without opening DevTools.
X-Frame-Options restriction: Many popular websites (Google, Twitter, GitHub, etc.) send an X-Frame-Options: DENY or Content-Security-Policy: frame-ancestors 'none' HTTP header, which prevents browsers from loading them in an iframe. If the preview is blank, the site has blocked embedding. For those sites, use your browser’s built-in Device Toolbar (Chrome DevTools → Toggle Device Toolbar, or press Ctrl+Shift+M).
This tool works best for previewing your own sites, local development servers, or sites that permit embedding. The iframe is sandboxed to prevent credential access and popups.