Yes, that's a cool website but it does not test on real mobile browsers, just shows a small frame inside your browser to see what your site will look like.
That's cool, but what I need is to run the website on different mobile browsers to see is it triggers some bug in the browser or looks different for some reason. Browser compatibility has done good progress in the last decade but is still not 100%.
So I want to test in virtual machines or on the real devices and running the real browser software. The question is, what devices and software should I test, because I can't test them all! I am already testing on Windows (desktop), with the browsers previously listed, and on Safari for iOS.
I can use
browserstack to test on emulated devices. They are expensive but give you a 30 minute free trial, and with some basic cheating, you can have enough of it. But they have many choices, and I don't know on which one I should concentrate, and which ones I should ignore because they're too rare or obsolete.