Click the desktop → press Cmd + - (minus) repeatedly to shrink icons.
If you don't have a mouse with a scroll wheel, or prefer preset sizes: how to make desktop shortcuts smaller
If your desktop icons feel too large, here’s how to shrink them in seconds. Click the desktop → press Cmd + -
Hold Ctrl on your keyboard and scroll down with your mouse wheel. Icons will get smaller instantly. how to make desktop shortcuts smaller
Scroll the to decrease the size or up to increase it. Method 2: Preset Menu Options (Quickest)
Here is a guide on how to make your desktop icons smaller on both operating systems.