Mac asks for password anytime a file copy is required

When your Mac prompts for a password during file copies, it is typically caused by a mismatch in file ownership permissions or an issue with the destination folder's Access Control Lists (ACLs). This usually occurs if you are copying files to/from external drives, root system folders, or folders restored from a backup (like Time Machine).

Follow these steps to eliminate the password requirement:

Fix Folder Permissions

If this is happening within your local user account (like your Desktop or Documents folder):

• Open Finder and right-click (or two-finger tap) the destination folder giving you trouble.
• Select Get Info. 
• Expand the Sharing & Permissions section at the bottom.
• Click the Lock icon and type your password to make edits. 
• Ensure your username is listed with Read & Write privileges. If it is not listed, click the Plus (+) button to add your user account. 
• Click the small three-dot circle icon at the bottom and select Apply to enclosed items. 

More info from Apple: Change permissions for files, folders, or disks on Mac - Apple Support

Clear Home Folder Permissions (Via Terminal)

If adjusting the info pane does not work, user account permission flags might be corrupted.

• Open the Terminal app (via Spotlight search or Applications > Utilities).
• Copy and paste the following command, then press return:

diskutil resetUserPermissions / `id -u`

• Restart your Mac and try copying the file again.

Check External Drive Settings

If you are copying files to or from an external hard drive or flash drive:

• Right-click the external drive icon on your desktop or Finder sidebar and choose Get Info. 
• Expand Sharing & Permissions at the bottom. 
• Check the box that says "Ignore ownership on this volume". This immediately stops macOS from checking user IDs on that specific drive