Sizzy is a browser extension for Chrome that complements the Sizzy app, which is designed specifically for responsive development. With Sizzy, developers can preview websites on multiple devices simultaneously, making it easier to test and optimize responsive designs.

The extension adds a convenient button to the Chrome toolbar. When clicked, the button opens the current URL in the Sizzy app, allowing developers to quickly see how their website looks on various devices and screen sizes. This can save significant time and effort in the development process, as developers no longer need to manually switch between different devices or resize browser windows.