
Description: Sizzy is a browser tool that allows web developers and designers to preview their websites on multiple device sizes simultaneously. It displays rezisions of the website on different device viewports like desktop, tablet, and mobile to help build responsive designs.
Type: Open Source Test Automation Framework
Founded: 2011
Primary Use: Mobile app testing automation
Supported Platforms: iOS, Android, Windows

Description: Responsinator is a free online tool that helps designers and developers test the responsiveness of their websites. It allows you to preview a site across various screen sizes like desktops, tablets, and phones to see how the design adapts on different devices.
Type: Cloud-based Test Automation Platform
Founded: 2015
Primary Use: Web, mobile, and API testing
Supported Platforms: Web, iOS, Android, API