How to make device friendly website without being responsive

Question

I've noticed most of the massive sites like Amazon for example, aren't really responsive, well it is responsive up until 1000px but after that it retains its fixed sites.

When they're opened in smaller devices for instance in mobile, they completely change their design and layout which in responsive websites aren't really possible.

1. How to design website like that?
2. Why do they choose it over responsiveness?
3. They certainly aren't using responsive design. Maybe a device dedicated CSS or whole website?

I was extremely curious but couldn't find anywhere in web. Thanks to anyone who can help.

Answer 1

They are using mobile redirect to their m.example.com subdomain or other domain. Am not sure but i think for huge css its not very efficient to include all the css for each device loaded for device that doesn't needs it.

For making it redirect based on devices you can use javascript: How redirect mobile users to different url?

And for making it responsive for some fixed range you can you max with and height values in css!

Edit: navigate to www.facebook.com on mobile and it will redirect to m.facebook.com automatically with a all new page specially built for mobile users, even better for low bandwidth connection it moves to mbasic.facebook.com which is even more basic and optimized for low bandwidth connection!