// the find
responsively-org/responsively-app
A modified web browser that helps in responsive web development. A web developer's must have dev-tool.
Responsively is an Electron desktop browser that loads one page into several device-sized previews at once, so a layout break on a phone, tablet and laptop shows up in one window instead of after repeated resizing. It is aimed at front-end developers iterating against a local dev server who would otherwise bounce between a browser and a resize handle.
Interactions are mirrored across every preview, so one click or keystroke exercises all the breakpoints at once, and the same surface is exposed through a built-in MCP server so coding agents can take per-device screenshots. The device catalog lives in plain data in deviceList.ts with support for custom devices, which keeps adding a viewport a small change. The test coverage is substantial for a project this size: more than forty Playwright e2e specs cover mirroring, device management, screenshots and the MCP bridge, and unit tests sit beside the code for URL validation, CSP and popup policy.
It is Electron, so each preview is a Chromium webview inside a Chromium shell, and memory use will climb with the number of devices open. The README gives no numbers here, so test it on your own machine before running eight devices at once. Mirroring also cuts the other way: a click that hits the right button in one viewport can land on a different element in another after the layout reflows, so a test sequence can fail for reasons that are not bugs in the page. Distribution is wide for a small team to keep healthy: Homebrew, Chocolatey, winget, RPM, AppImage, a separate browser extension and a separate npm MCP package each have their own publish workflow.