The resolution (in pixels by pixels) of your Mac screen determines how much information you can fit on the screen and how sharp the image is, so it’s important to know. If you are running a full screen game or an application with original resolution, the image will look its best, so here you can find out what it is.
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First, click the Apple icon in the upper left corner of the screen and select “About This Mac.”;
Click on the “Screens” tab in the window that appears.
On the next screen, you will see information about the screen (or screens) you have built in or connected to your Mac.
The screen resolution is the set of numbers indicated in parentheses exactly after the size of the screen. For example, the list here says “27-inch (2560 x 1440)”, which means that 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 original (ideal) resolution on the screen regardless of the resolution settings in System Preferences.)
If you have more than one monitor connected to your Mac, you will see them all in this window. Here is an example. With an external monitor, you will find its original resolution listed just below its name.
Now that you know the original resolution of your monitor, you can use it to run games in the best possible quality, find wallpapers that fit your monitor exactly and more.
If you need to adjust your resolution settings, About This Mac makes it easy. Just click the “View Settings” button in this window and you will be taken directly to the “System Settings” where you can adjust your screen settings to suit your needs.
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