Use Finder preferences to set options for Finder windows, file extensions, and the Trash.
To view Finder preferences, click the Finder icon in the Dock, then choose Finder > Preferences.
Show these items on the desktop
Select any items you want to see on the desktop.
New Finder windows show
Choose which folder is displayed when you open a new Finder window.
Open folders in tabs instead of new windows
Select what happens when you press and hold the Command key and double-click a folder.
Show these tags in the sidebar
Customize the tags you see in the Finder sidebar.
Customize the tags you see in the shortcut menu that appears when you Control-click a file.
For more information about tags, see Use tags to organize files.
Show these items in the sidebar
Select the items you want to see in the Finder sidebar.
These items also appear in Open and Save dialogs.
Show all filename extensions
A filename extension—the period followed by a few letters or words that you see at the end of some filenames (for example, .jpg)—identifies the type of file. This option affects most, but not all, filenames.
Show warning before changing an extension
Display a warning if you accidentally try to change an extension. As a rule, you shouldn’t change filename extensions.
Show warning before emptying the Trash
Display a warning so you don’t accidentally delete items in the Trash.
Remove items from the Trash after 30 days
Remove items permanently 30 days after being moved to the Trash.
Keep folders on top when sorting by name
Lists folders in alphabetical order first, then files alphabetically when arranging by name.
When performing a search
Choose what you want to search by default when you use the search field in Finder windows. You can search your entire Mac, the folder that’s currently open, or the scope you specified the last time you searched in a Finder window.
For even more ways to customize Finder windows, see Customize the Finder toolbar and sidebar.