Dual Preview: Mobile View & Responsive Tester

See mobile and desktop views side-by-side. The ultimate responsive web tester and mobile simulator for faster frontend workflows.

Stop guessing how your website looks on a phone. Dual Preview is a free Chrome extension that shows you mobile and desktop views side-by-side — instantly, in one window, on any website. Up to 80% of web traffic is mobile, yet most of us still review and approve websites on a desktop screen. That means broken layouts, wrong font sizes, and cut-off buttons go live without anyone noticing. Dual Preview fixes that — paste any URL and see exactly what mobile users see, right next to the desktop version. No technical setup. No DevTools. No resizing windows. Just open it and see. EVERYTHING YOU NEED: • Side-by-Side in One Click: Paste any URL and instantly see mobile and desktop simultaneously. Works on your own site or any website. • Real Device Viewports: Preview how your site looks on iPhones, Pixels, and Samsung devices your users actually own. • Mobile Simulator with Phone Frame: See the page inside a real-looking iPhone frame — just like your users do. • Multiple Panels: Compare three screen sizes at once or run two breakpoints in parallel. • Screenshot Both Views: Capture mobile and desktop in one image. Share in Slack, drop into Figma, paste into a ticket. • QR Code to Your Real Phone: Scan any URL straight to your phone and feel the actual experience in your hand. • PageSpeed Check: One click from any panel to PageSpeed Insights — no copying URLs. WHO IT''S FOR: • Product Owners & Managers: Show stakeholders what mobile users actually see. No more approving desktop layouts and calling it done. • UX/UI Designers: Check your designs against real mobile screens as you work. Benchmark competitors with a single paste. • Content & Marketing Teams: Preview landing pages, articles, and campaign creatives on mobile before hitting publish. • Developers: Catch responsive bugs without toggling DevTools back and forth. Free. No account. Works on any website. WHY THESE PERMISSIONS? • All URLs & browsing history — required to load any website inside the preview panels and to show URL suggestions in the address bar. • Debugger — used exclusively by the built-in Performance Audit feature to measure real page load times and Core Web Vitals via Chrome DevTools Protocol. Never used to read or modify page content. • Cookies & browsing data — used only to clear the cache for the currently previewed site when you request a hard reload.