Use Disk Utility to create a compressed disk image
Easily produce a portable copy of your most important files
creating a compressed disk image might sound complicated, but essentially it involves creating a single file that contains a copy of any folder on your Mac’s hard drive. For a one-off backup of your most important data it’s a great option and entirely free.
1 Select folders or files
Fire up Disk Utility, head to File>new image>image from Folder and select the files or folder you want to include in your compressed disk image. you might want to organise these into a single folder.
2 Name and create
in the Save dialog that appears give your disk image a logical name, select where to save it to and ensure that the image Format is set to ‘compressed’. When you’re ready click ‘Save’.