This is a really handy tool, and although it sometimes has trouble loading the site, in my tests, when it does, it works very well.

With Resizer you can input a custom URL, or preview selected websites and demos. Using the action icons, you can view a site across Material Design breakpoints for desktop and mobile. Google Design Resizer For Responsive Layouts [design.google.com]

Try the resizer here [design.google.com...]