Responsive Viewer - View multiple screen dimensions in one view
Responsinator - Designed to test responsive websites on different devices.
Gravity Flow - Business process automation for WordPress
LT Browser by Lambdatest - LT Browser is a free dev friendly browser for developers and testers. You can see mobile view of website on different screen sizes and resolution on 50+ pre installed view ports. You can build, test and debug your website faster then ever.
Responsive Website Test - Test any website on desktop, mobile, and tablet
Rapid Responsive Design - Kill your artboards, design for all sizes faster