Modern apps and websites should look great on Retina displays, so we have to test them in both standard and ultrahigh resolution modes. But when you configure your display in System Preferences, it takes plenty of time to switch from the standard to the HiDPI mode and vice versa. ResolutionTab is a minimal app living in the menu bar that toggles your Mac between Retina and non-Retina resolutions in one click.
Please Note: In order to use ResolutionTab, you need Xcode and a developer tool named Quartz Debug that enables virtual HiDPI modes in OS X.
Assuming you already have Xcode installed, here’s how to install Quartz Debug: