Monochrome

Monochrome is a modern browser that brings mobile web apps to desktop.

Monochrome lets you browse and check all your favorite social networks at the same time from the ease of your laptop. You can listen a song on SoundCloud or watch an YouTube video while working on something else without the battery taking a huge hit.
The fixed viewport of 320px (width) × 528px (height) is simulating Apple's iPhone 5.

Note: While the app is free, consider donating to stimulate app development.