Dual Mobile Viewer

About

Dual Mobile Viewer helps front-end developers, web publishers, and planners preview the current page in a desktop window and a mobile-sized window at the same time with a single click.

Key features
One-click mobile window — Choose a device preset in the popup and open a mobile-sized popup window next to your current window.
22 device presets — Smartphones and tablets including iPhone, Galaxy, Pixel, iPad, and Galaxy Tab viewport sizes.
Mobile User-Agent (mobile window only) — The mobile window sends requests with the selected device User-Agent and Client Hints, useful for responsive CSS and server-side mobile routing (e.g. m. subdomains).
Original window unchanged — Your desktop window size and environment are not modified.
Who it’s for
Developers validating responsive layouts quickly
Planners and marketers comparing desktop vs mobile UI
Publishers who want side-by-side comparison without switching DevTools device mode
Known limitations
Sites that detect devices via JavaScript (e.g. Gmail) may still show desktop UI.
The actual CSS viewport in the mobile window may differ slightly from the preset due to browser chrome (address bar, etc.).