Screenshot Format on the Terminal of the Mac change
The file Format for Screenshots to permanently change, go the way of the prompt, the so-called "Terminal".
- You can open the Spotlight search (cmd + spacebar) and type "Terminal". Confirm with "Enter".
- Type the command "defaults write com.apple.ScreenCapture type JPG; killAll SystemUIServer" key and press the Enter key. Alternatively, you can also choose a different Format than JPG, for example, PDF, GIF, or TIFF. To do this, you replace the "JPG" in the command against the appropriate Format.

Mac Screenshot Format change
How different Screenshot types using the keyboard shortcut to create read in this article.