Free Responsive Web Design Tool by Google. Test your websites on mobile.
FYI: You can Build Responsive Websites Easily, try Responsive Builder in action! Get Responsive Website Builder >>
Responsive mobile test by Google tools:
Basic link: https://www.google.com/webmasters/tools/mobile-friendly
+
/?url=http%3A%2F%2FYOURWEBSITE%2Findex.html
//add my website url
=
https://www.google.com/webmasters/tools/mobile-friendly/?url=http%3A%2F%2FYOURWEBSITE%2Findex.html
= free responsive website tester
Tested template: Template preview
Screenshot:

Pros: It’s Free, Online, test with URL, you can immediately send the link to a client or friend or embed on your page.
Cons: it’s goooogle