For a very long time, Google Chrome didn’t have a tool for developing responsive web pages, so majority of people learned to use various plugins. But now, Chrome has a tool for developing responsive sites – right in its DevTools.
You can access them pretty easily – just push F12 and then ESC, so JavaScript console pops up. There is tab called Emulation, where you can select a device and emulate it, or set your own properties.
You should refresh the page after changing resolution.
Chrome can also emulate accelerometer, geolocation coordinates and touch events.