An NRG file contains a CD or DVD disk image created with Nero disc authoring software. It may be an exact copy of a CD/DVD or may contain a collection of files that can be mounted as a disk. NRG files are often used to make copies or backups of discs or important data.

While NRG files are typically created and opened using Nero software, they can be opened by a variety of programs for Windows, macOS, and Linux. Some of the programs include HH Software Virtual CD, EZB Systems UltraISO, Smart Projects IsoBuster, and Roxio Toast. NRG files can also be converted to the more popular .ISO format using the free Nrg2Iso or NRG to ISO utilities. Simply select the NRG file you want to convert in the program, click Convert, and save the ISO file.