Responsively App for Mac

Quick introduction to the macOS responsive tester

Responsively is a free utility built for macOS users who build websites and web apps. It creates a focused workspace for checking and troubleshooting layouts across several device views at once, helping you spot and fix responsiveness issues faster.

Core capabilities

• Linked scrolling and replicated interactions across all previews so you can test behavior simultaneously.
• Adjustable device profiles with custom screen sizes and user agents to match the machines and viewports you care about.
• Live previews that update instantly as you change code, allowing on-the-fly validation of layout tweaks.
• Side-by-side multi-device display so you can compare how a page renders on phones, tablets, and desktops at the same time.

How it improves your workflow

By showing multiple viewports in real time, the app reduces context switching and accelerates debugging. Designers and developers can confirm that styles respond correctly across breakpoints without continually resizing windows or deploying to separate devices. The straightforward interface and focused feature set make the process of refining responsive layouts more efficient and predictable.

Other options to consider

• CheatSheet — a free alternative worth trying for quick reference and lightweight viewport checks.
• Viewport Resizer — a browser-based bookmarklet/tool for ad-hoc testing across common screen sizes.