There used to be a free third-party tool to 'mount'. Note: When referring to optical discs the correct spelling is disc, when referring to a hard disk or SSD disk drive the correct spelling is disk. toast disc image file, then use Disk Utility to make a. You would use the Toast software to 'mount' the. dmg format then you will likely still need the Toast software. If you merely want to access the contents or burn the contents to an optical disc then the easiest option is to use the same Toast software. Such a file usually contains the contents of a CD-ROM or DVD or Blu-Ray. toast file is basically equivalent to a disk image file i.e.dmg but is created by the Toast software rather than the Disk Utility software.
