Responsively App: an Electron browser that mirrors your clicks across every device preview

The problem Responsively App addresses: one page, many viewports, one set of actions

The standard loop for checking responsive CSS is tedious. You open a browser, resize the window, scroll to the section you are working on, open dev tools, inspect an element, then repeat the whole sequence at the next breakpoint. Each resize loses your scroll position and your selection. Responsively App exists to collapse that loop. The README describes it as "A modified browser built using Electron that helps in responsive web development," and the feature list is built around that single idea: mirrored user interactions across all devices, a customizable preview layout, one elements inspector for all devices in the preview, 30+ built-in device profiles with custom device support, one-click screenshots on all devices, and hot reloading for developers.

The intended user is a front-end developer working on layout, breakpoints or component behaviour. Someone debugging a server-side rendering bug or a WebSocket handshake gets nothing from it. The tool is about visual layout across widths, and its value scales with how much of your day is spent on that.

How the mirrored preview actually works

The architecture is a desktop application shell (Electron) that hosts multiple web contents, one per device profile. The README does not publish an internal architecture diagram, but the feature list makes the data flow legible. Each device profile is a viewport definition: a width, a height, and a user agent string. The app renders the same URL into every active viewport simultaneously. When you scroll, click or type in one pane, the event is replayed in the others, which is what "mirrored user-interactions across all devices" means in practice. The elements inspector is shared, so selecting a node in one viewport highlights the corresponding node in the others.

The device profiles are the second half of the mechanism. Responsively ships 30+ built-in profiles and lets you add custom ones. A custom device is a named viewport with its own dimensions and user agent, which matters because a CSS media query can be triggered by width while a server can return different markup based on the user agent string. If your custom profile only sets a width, you are testing the media query and not the user-agent branch. That distinction is worth keeping in mind before you conclude a layout is fine everywhere.

Hot reloading is listed as a feature, which implies the app participates in the dev-server workflow rather than replacing it. You still run your own bundler; Responsively App is the viewing surface.

Installing Responsively App and running a first mirrored preview

The README points to responsively.app/download for Mac, Windows and Linux builds. Package managers are documented for each platform. On macOS, the Homebrew cask is the shortest path:

brew install --cask responsively

After it completes, the app appears in Applications. Windows users have two documented options, Chocolatey and winget:

choco install responsively

winget install ResponsivelyApp

Linux users on RPM-based distributions can install the published package directly, substituting the version you want:

sudo rpm -i https://github.com/responsively-org/responsively-app/releases/download/v[VERSION]/Responsively-App-[VERSION].x86_64.rpm

If you are not on an RPM-based distribution, the README directs you to the releases page for an AppImage instead. The README does not document a Flatpak, Snap or native .deb package, so Debian and Ubuntu users should expect to use the AppImage or build from source.

For the first real use, start your own dev server as usual, then launch Responsively App and enter the local URL, for example http://localhost:3000. Add two or three device profiles from the built-in list, ideally one narrow phone, one tablet and one desktop width. Scroll in any pane and confirm the others follow. Open the shared inspector and click an element; the selection should appear across the previews. Then use the one-click screenshot action to capture all devices at once, which is the fastest way to see whether your breakpoints are actually doing what you think. The README also documents browser extensions for Chrome, Firefox and Edge that send the current link from your browser into the app, which is useful when you are browsing a staging URL and want to inspect it without retyping.

Where Responsively App stops being the right tool

The most important limitation is the one the marketing framing obscures: this is a desktop Electron browser rendering on your machine. It is not a real device. A viewport with a phone's dimensions and user agent string does not reproduce a phone's GPU, its touch event model, its font rendering, its memory pressure or its network conditions. If your bug only appears on a physical iPhone or a low-end Android device, Responsively App will not surface it, because the rendering engine is the same desktop Chromium underneath.

There is a second, quieter limitation. The README does not document a command-line interface, a headless mode or a CI integration. Cross-browser grids exist precisely to run these checks unattended on every commit; Responsively App is an interactive desktop tool. If your requirement is "fail the build when the layout breaks at 375px," this is the wrong category of software.

The repository is also not under rapid development. The last push was on 2026-02-17, roughly seven months before this writing, and the most recent release listed is v1.18.0 on the same date. That is not abandonment, but it is slow enough that you should not expect a fix for a niche bug to arrive quickly. The README does not document a rollback procedure or a downgrade path if a new release regresses your workflow, so pin the version you install if that matters to you.

Responsively App compared with Polypane and cloud device grids

The obvious comparison is Polypane, which people search for directly. Both are desktop tools that show one page in several viewports at once, and both target the same developer. The difference in approach is licensing and packaging rather than the core idea: Responsively App is AGPL-3.0 and free to download from responsively.app, while Polypane is a commercial product. If your constraint is cost or you want to read and modify the source, that difference decides it. If your constraint is a specific accessibility or debugging feature set, the two are not interchangeable and you should compare feature lists directly rather than assume parity.

The other alternative is a hosted device cloud, the kind of service that runs your page on real phones and tablets in a remote lab. Those solve a genuinely different problem: real hardware, real browsers, real network conditions, plus the ability to run the same checks in CI. Responsively App solves the fast local loop. Many teams reasonably use both, but if you only have budget for one and your bugs are device-specific rather than width-specific, the cloud grid is the one that will find them.

A third option is simply your existing browser's responsive design mode. It is already installed, it has a device list, and it costs nothing. Responsively App's advantage over it is the simultaneous multi-viewport view and the mirrored interaction, which is a real workflow gain when you are iterating on a breakpoint-heavy layout. It is not a gain when you are checking a single width once.

Licence, maintenance and what upgrading costs you

Responsively App is licensed AGPL-3.0. For a developer running the desktop app locally, that is unremarkable. The copyleft obligation becomes relevant if you modify the source and distribute it, or if you run a modified version as a network service that users interact with. The AGPL's network clause is the part that surprises people, and it is the part worth reading before you fork the desktop-app directory and ship a derivative. This is a description of the licence text, not legal advice; if you plan to redistribute, get your own review.

On maintenance, the repository is not archived, but the last push was on 2026-02-17 and the latest release in that same window is v1.18.0, whose notes mention a design mockup overlap feature and bug fixes. The release before it, v1.17.1, arrived on 2025-10-11 with detailed site permissions and new devices. That cadence suggests a mature project in maintenance mode rather than one adding large new subsystems. Upgrading is a desktop application update, not a dependency bump: there is no lockfile to reconcile and no migration script in the README. The practical cost is regression risk in your own workflow, and the README does not document a downgrade path, so keep the installer for your current version if you depend on specific behaviour.

Editorial conclusion

Adopt Responsively App if you write CSS or markup daily and want to see one page in several viewports while scrolling and clicking once. Do not adopt it if you need real device testing, CI integration or a hosted cross-browser grid; it is a modified Electron browser on your machine, not a device lab. Before relying on it, verify the AGPL-3.0 obligations against your own distribution model, confirm the release you install matches the version you intend to pin, and check that the built-in device profiles cover the breakpoints your project actually targets.

Frequently asked questions

Official sources

1. Official documentation
2. Official README
3. Project repository
4. Release notes