.iso

ISO is a common disk image format that has been standardized by the International Organization for Standardization (ISO). The name comes from the ISO 9660 file system used by CD-ROM media. An ISO file contains an exact copy of all data from a disc, such as CD or DVD.

Since ISO files contain exact copies of physical discs, they can be used to make multiple copies of discs. Most disc authoring software programs support the ISO format, allowing them to burn the data from an ISO file to a physical disc. Since ISO is a widely supported file type, it is an ideal format for backing up data.