This is a free to use for any projects (personal & commercial) template which contains the major breakpoints present in the Bootstrap 3 example pages from mobile to widescreen desktop.
A free collection of popular phones, tablets and displays for product mockups.
Ionic is a beautiful front-end framework for developing hybrid mobile apps in HTML5. Free and open source, Ionic offers a library of mobile-optimized HTML, CSS and JS components for building highly interactive apps. Built with Sass and optimized for AngularJS.
It doesn’t matter how brilliant your work is if people can’t see it. Now everything you create is accessible on any screen – desktop, tablet or mobile – without compatibility issues.