Lax.js - Create beautiful & smooth animations when you scroll
Responsive Website Test - Test any website on desktop, mobile, and tablet
ScrollMagic - The jQuery plugin for magical scroll interactions.
Responsive Viewer - View multiple screen dimensions in one view
WOW.js - Animate elements on-scroll to catch attention. Such Magic.
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.