Responsively App is a free, open-source browser designed for responsive web development that displays a web page across multiple device viewports simultaneously with synchronized interactions. It solves the inefficiency of testing responsive layouts by allowing developers to view and interact with their site on multiple screen sizes at once, with all viewports mirroring scrolling, clicking, typing, and navigation in real time. Responsively dramatically accelerates the responsive development workflow by eliminating the need to constantly resize browser windows or switch between device emulations.
Responsively provides a curated library of device presets covering popular phones, tablets, and desktop resolutions, synchronized browsing where interactions in one viewport are mirrored across all others, a built-in element inspector, screenshot capture across all viewports simultaneously, hot reloading support for instant feedback during development, and customizable viewport layouts. It also features a network throttling simulation, user agent spoofing per device, and the ability to add custom device dimensions for testing specific viewport requirements.
Responsively is ideal for frontend developers and web designers who regularly build responsive websites and need a faster alternative to Chrome DevTools' device emulation mode. It is available as a standalone desktop application for Windows, macOS, and Linux, and works with any local or remote web server. Responsively is particularly popular among freelance developers, web agencies, and frontend teams who need to quickly verify responsive layouts across multiple breakpoints without the overhead of a paid browser tool, making it an excellent free alternative to commercial tools like Polypane.
