The resolution (in pixel by pixel) of your Mac’s display determines how much information you can fit on the screen and how sharp the image is, so it’s important to know. If you’re running a game or full-screen app at its native resolution, the images will look their best, so here’s how to find out.
First, click the Apple icon in the upper left corner of the screen, and select “About This Mac”.
In the window that appears, click the “Displays” tab.
On the next screen, you’ll see information about any views (or views) you already own or have attached to your Mac.
Screen resolution is a set of numbers enclosed in brackets immediately after the display size. For example, the listing here says “27-Inch (2560 x 1440)” which means the Mac in this image has a 27-inch screen with a resolution of 2560 x 1140 pixels.
(Note that “About This Mac” always displays the native (ideal) resolution of the screen regardless of the resolution setting in System Preferences.)
If you have more than one display attached to your Mac, you’ll see them all in this window. Here’s an example. With an external display, you’ll find its native resolution listed just below its name.
Now that you know the native resolution of your screen, you can use it to run games at the highest quality, find a desktop wallpaper that really fits your screen, and much more.
If you need to adjust your resolution settings, About This Mac makes it easy. Just click the “Displays Preferences” button in this window, and you will be taken directly to “System Preferences” where you can change the display settings to suit your needs.