Quick Verdict
Use ISO when…
Use ISO for CD/DVD images — installing operating systems, burning discs, or accessing optical media archives. ISO is universally supported by mounting tools and burning software.
Use IMG when…
Use IMG for generic raw disk images — SD card backups, hard drive captures, embedded device firmware. IMG can hold any file system, which makes it more flexible but less universally readable.
ISO vs IMG: Feature Comparison
| Feature | ISO | IMG |
|---|---|---|
| File system | ISO 9660 (or UDF) | Any (FAT, ext4, NTFS, HFS+) |
| Source media | CD/DVD/Blu-ray | HDD, SSD, SD card, USB drive |
| Mounting on Windows | Native (right-click Mount) | Requires tool (OSFMount, ImDisk) |
| Mounting on macOS | Native | May need conversion to DMG |
| Burning to disc | Standard CD/DVD software | Requires conversion to ISO first |
| File extension consistency | Always .iso | Sometimes .img, .raw, .bin |
When ISO wins
- ✓File system: ISO 9660 (or UDF)
- ✓Source media: CD/DVD/Blu-ray
- ✓Mounting on Windows: Native (right-click Mount)
When IMG wins
- ✓File system: Any (FAT, ext4, NTFS, HFS+)
- ✓Source media: HDD, SSD, SD card, USB drive
- ✓Mounting on Windows: Requires tool (OSFMount, ImDisk)
Frequently asked questions
Are ISO and IMG interchangeable?
For CD/DVD images, often yes — many .img files are actually ISO 9660 images with a different extension. For raw drive images (USB, SD card), they're not interchangeable; IMG can hold any file system, ISO only ISO 9660 or UDF.
How do I convert IMG to ISO?
If the IMG is actually ISO 9660: just rename `.img` to `.iso`. If it's a raw disk image with a different file system, you can't directly convert — you'd need to extract the contents and create a new ISO from them with mkisofs/genisoimage.
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More comparisons
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