Screen resolution is the number of pixels that your iMac can display. Usually, the number is defined in terms of Width x Height (e.g. 1920x1080, 1200x 720). Higher pixels assure that text, videos and images appearing on your screen will be sharp and clear. If you want to adjust screen resolution in iMac, here are the few steps that you need to follow:
Step 1: Click on Apple menu and choose "System Preferences". By default, Mac OS will choose the best resolution for your display to provide clear and crisp image. You can easily adjust resolution of objects appearing on your screen.
Step 2: Click on "Displays" option and then further click on "Display" tab to adjust the display as per your preference. You will find two option “Best for display” and “scaled”. Select “Scaled" if you want to adjust screen resolution manually.
Step 3: After selecting the appropriate resolution wait for the screen to adjust with new screen resolution setting. Don’t forget to restart your iMac after performing all these steps.