Select the ‘General’ tab, and then select the ‘Show a message when the screen is locked’ checkbox.

Click the little padlock icon in the bottom-right corner of the screen, and enter your username and password.

To create a message that’ll be displayed on your login screen: If you want to switch back to your original wallpaper at any point, then simply drag the original image file back into the /Library/Caches folder, and select ‘Replace’ when prompted.

If you lock your Mac rather than logging out completely, then you may still see your original background – although this behaviour seems to vary depending on the version of macOS you have installed. Your Mac will now use this image as the background for your login screen, however note that this image will be displayed on the login screen only. Once you’re happy with your modified file, save it.Paste your image over the file’s contents.Open the image you want to use as your login background, in any image-editing program.Open the file in any image-editing program.To make sure you can switch back to this default at any point, make a copy of this file and then store it somewhere safe.

The ‘Caches’ folder should contain a file.Enter the following text /Library/Caches, and then click ‘Go.’.Select ‘Go > Go to Folder’ from the toolbar.How To Customize Login Screen Background on Mac OS

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