Is it the smartphone or the website that makes a website display the mobile version?

My smartphone has a 1920*1080 resolution. Since that's a typical desktop screen resolution, why doesn't a website adjust to the full-sized page?

And if it's because of device information sent by the browser, why does "Request Desktop Version" on mobile Chrome seem to not work on pages with responsive design?

Or is it because smartphones act like Macs with Retina displays, scaling so that a 2880 * 1800 resolution acts like 1440*900?

Epic visual tool

Epson 5030UB 2D/3D 1080p 3LCD Projector Submitted September 28, 2015 at 03:50AM by dancrafty http://ift.tt/1iDHDOF