UXsniff - Track user behavior on your website and improve conversions with UXsniff: the user experience watchdog that looks out for you.
Responsive Viewer - View multiple screen dimensions in one view
Atlassian Design - Design, develop, and deliver
Responsive Website Test - Test any website on desktop, mobile, and tablet
The Adventures of UX Hero - The world’s first User Experience comic series
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.