Responsively

About

Responsively is a free, open-source DevTool for web developers who build responsive web apps. It lets you see all devices at once, side-by-side, without fiddling with the devtools resizer. Any click, scroll, or navigation you perform on one device is replicated to all devices in real time.

You can save your favorite device combinations as Preview Suits and switch between them quickly while testing. Responsively includes a large collection of device profiles out of the box, and you can also add your own custom devices.

It also includes utilities such as the Unified Inspector, which lets you inspect elements across all devices at once by pressing Cmd/Ctrl + I and hovering over an element. You can take full page screenshots of all devices at once, screenshots of individual devices, or a quick screenshot of the viewport. Basic browser features like cookie management, local storage, session storage, and bookmarks are also available, and you can use the devtools as you would in any browser.