Mobile Simulator (Self-Hosted)

Responsive testing tool — preview any site on multiple device frames side by side. Free & local.

A free, local Chrome extension for responsive testing. Shows any site on multiple devices side by side, with real device frames, rotation, zoom, and a mobile User-Agent. Quick usage guide Open it: click the extension icon on any site (opens with the current URL), or open simulator.html directly from the extension. Pick devices: the chips at the top toggle devices on/off. "+ Custom" adds a device of any size. Load a site: type a URL in the top bar and hit Go (or Enter). All active devices load in parallel. Zoom: the slider scales all devices together; ⛶ Fit auto-computes the zoom that fits everyone on screen. Rotate: the ⤾ button next to each device, or "Rotate all" for everyone at once. ⤢ Focus: pops a single device to 100% zoom, full screen; Esc exits. Sync: on by default — scrolling/clicking/typing/navigating on one device replays on all the others. Turn it off to test each device independently. 📸 / 📋: capture the whole stage to a file or straight to the clipboard. 🌐 Envs: compare the same page across environments (prod/dev/staging) — every base URL you type is saved permanently in a library; tick which ones join the comparison. 🐢 Throttle: simulates a slow connection to check loading states and spinners, without touching real network conditions. ⏺ Replay: record a usage scenario once, then replay it on every device with one click. 🎨 Figma Overlay: drag a PNG export from Figma onto a device and compare pixel-for-pixel with opacity/Diff. Console + Network: the bottom dock centralizes logs and network requests from every device in one place, filterable per device. Full detail on every feature, including how it's built, is in the Features and How it works sections below. The in-app ? Instructions button covers the same ground without leaving the extension.