Free online ISO to IMG converter

A virtual machine, flashing utility, or imaging program may require a disk image named .img instead of .iso. When the program accepts the same raw image data, the safest conversion is a rename or byte-for-byte copy; changing the extension does not change the image contents.

What the ISO format is

ISO is a disk-image format most commonly used for CD, DVD, and Blu-ray media. It normally contains an ISO 9660 filesystem, often alongside Joliet or UDF metadata, and may include boot sectors, directory structures, multisession data, and unused sectors. Operating-system installers, software distributors, disc-authoring tools, and imaging utilities commonly use .iso files.

Windows, Linux, and macOS can usually mount an ISO as a virtual optical disc. Extracting the files is not equivalent to converting the image: extraction can discard boot records, filesystem metadata, session information, and unused sectors.

What the IMG format is

.img is a generic extension for a sector-by-sector disk image, not one specific filesystem or standard. An IMG file can represent a floppy disk, memory card, hard drive, optical disc, virtual machine disk, or removable-media image containing FAT, exFAT, ext4, ISO 9660, UDF, a partition table, or another structure.

IMG is useful when software accepts raw media images but rejects an ISO filename. It does not automatically compress the source, reduce its size, or adapt an optical-disc image to the partition layout and boot requirements of a memory card or hard drive.

Convert by renaming when the data is already compatible

Check the target program's documentation first. If it accepts an ISO image internally but requires the .img extension, rename the file:

• Windows: enable file extensions in File Explorer, then rename disk.iso to disk.img.
• Linux or macOS: run mv disk.iso disk.img.

Renaming changes only the filename. It does not rewrite, repair, compress, or convert the sectors.

Create a separate byte-for-byte IMG file

Use a copy when you need to retain the original ISO. On Linux, run:

dd if=disk.iso of=disk.img bs=4M status=progress conv=fsync

On macOS, run:

dd if=disk.iso of=disk.img bs=4m

On Windows PowerShell, run:

Copy-Item -LiteralPath .\disk.iso -Destination .\disk.img

These operations preserve the bytes, including boot information and unused sectors. Confirm that the files have the same checksum:

sha256sum disk.iso disk.img

On macOS, use shasum -a 256 disk.iso disk.img. On Windows, use certutil -hashfile disk.iso SHA256 and repeat the command for disk.img. Matching SHA-256 values prove that the two files are identical.

Use a desktop or online converter

A disk-imaging application can create an IMG output when the destination software requires a newly written image rather than a renamed file. Select the ISO as the source, choose IMG or raw image as the output, select a destination with enough free space, and start the operation. Do not choose file extraction or DVD-video conversion if preserving a bootable disc image is required.

You can also convert the file on 101convert.com for free without installing software: upload the ISO, select IMG, start the conversion, and download the result. Do not upload confidential images, and verify the downloaded file before using it.

Compatibility limits

A byte-for-byte ISO-to-IMG result has the same quality and boot data as the ISO, but an .img extension cannot make incompatible data usable. A program may require a hard-disk image with a partition table, a specific sector size, or a filesystem intended for its device; a typical optical ISO may not contain those structures.

Do not write an ISO-derived IMG directly to a memory card or disk unless the image is designed for that device. Writing overwrites the destination. Keep the original ISO until the IMG has passed checksum and device tests.

CloneCD files are a special case

CloneCD commonly uses an .ccd descriptor, an .img data file, and sometimes a .sub file. The CloneCD .img is not simply a universal IMG format, and renaming an ISO does not create the required descriptor or subchannel data. Use imaging software that explicitly supports CloneCD output when those accompanying files or protected-disc metadata are required.