The Identification Vector
By default, macOS aggressively hides file extensions (the three or four letters following the period at the end of a filename, such as .jpg or .pdf). Apple implements this to create a cleaner, less intimidating user interface. However, for developers, graphic designers, or anyone managing complex file systems, hiding extensions creates a massive security and organizational vulnerability. Without seeing the extension, it is incredibly difficult to distinguish between a harmless image file (document.png) and a potentially malicious script disguised as an image (document.png.sh).
How to Show File Extensions
You can force the Finder to globally reveal the true extension of every single file on your hard drive.
1. Ensure you are currently on the Desktop and the Finder application is active (look at the top-left corner of your menu bar).
2. In the top menu bar, click on the word Finder.
3. Select Settings… (or Preferences on older macOS versions) from the dropdown menu.
4. In the Settings window that appears, click on the Advanced tab (indicated by a gear icon).
5. At the very top of this menu, locate the checkbox labelled Show all filename extensions.
6. Click the checkbox to place a tick mark inside it.
The Finder will immediately update. Every file across your entire system will now display its true extension, providing absolute clarity and preventing accidental execution of incorrect file types.