Free online IMG to ISO converter

Some burning tools, virtual drives, operating systems, and boot utilities require an ISO instead of an IMG. Converting the image can provide a compatible file for mounting, burning, archiving, or sharing, but only an optical-disc IMG can usually be preserved as an equivalent ISO.

What the IMG format is

In the disk-image context, .img is a generic extension for an image of a floppy disk, optical disc, hard-disk partition, memory card, USB drive, or other storage device. It does not identify one standardized internal format: an IMG may be a raw sector copy, an optical-disc image using ISO 9660 or UDF, or a format associated with a particular imaging application.

IMG files are commonly created by dd, Raspberry Pi Imager, Win32 Disk Imager, backup utilities, forensic tools, emulator software, and CloneCD-related applications. They appear in operating-system downloads, bootable-media projects, removable-media backups, and older software distributions.

What the ISO format is

An ISO is an optical-disc image, normally containing an ISO 9660 or UDF filesystem and, when applicable, boot metadata such as an El Torito boot image. Windows, macOS, Linux, virtual-drive software, disc-burning programs, and many backup tools support ISO directly.

ISO is the appropriate target when the destination expects a CD, DVD, or compatible Blu-ray image, or when the file must mount as a virtual optical disc. ISO is not automatically smaller than IMG; a direct image copy generally preserves the same sectors without compression.

Check the IMG before converting

On Linux or macOS, inspect the file with:

file input.img

If the output identifies ISO 9660 or another optical-disc filesystem, the file may already be an ISO image with an .img extension. After confirming that the image is an optical-disc image, a byte-for-byte copy is sufficient:

cp input.img output.iso

For a large file, this also works on systems whose dd supports progress reporting:

dd if=input.img of=output.iso bs=4M status=progress

Renaming input.img to input.iso changes only the filename. It does not convert a floppy, partition, USB, or hard-disk image into an ISO.

Convert with desktop software

AnyToISO can convert supported IMG and other disc-image files to ISO on supported desktop systems. PowerISO provides similar image-opening and export functions, primarily on Windows. Menu names vary by version.

1. Open the image utility and choose its image conversion or image-to-ISO function.
2. Select the .img file as the source.
3. Choose ISO as the output format and specify a destination such as output.iso.
4. Enable boot-sector preservation only if the source is a bootable optical-disc image and the program offers that option.
5. Start the conversion, then mount or open the resulting ISO to check its contents.

For a CloneCD image, the .img may depend on companion files such as .ccd and .sub. The command-line utility ccd2iso can convert compatible CloneCD images:

ccd2iso source.img output.iso

Do not treat ccd2iso as a universal IMG converter; it is intended for a specific optical-disc image layout, and omitting required companion data can produce an incomplete result.

Rebuild an ISO from readable files

If the IMG contains a readable filesystem but is not itself an optical-disc image, mount or extract it first, then create a new ISO from the extracted directory with xorriso:

xorriso -as mkisofs -o output.iso extracted-files/

This creates a new disc image rather than preserving the original sectors. To retain bootability, supply the original boot image and the correct El Torito options; copying visible files alone can remove boot code, volume identifiers, permissions, timestamps, hidden files, multisession data, or copy-protection information.

For a conversion without installing desktop software, 101convert.com can convert supported files online for free. Uploading a large, private, or boot-critical disk image may be unsuitable, and an online converter may reject raw disk images or images requiring companion files.

Quality and compatibility limits

A direct copy preserves every source byte, including unused sectors and boot information, but it is useful as an ISO only when the IMG already has a compatible optical-disc layout. A raw hard-disk, partition, floppy, SD-card, or USB image can contain partition tables and geometry that ISO does not represent; converting it may make the result unbootable or discard the original layout.

After conversion, mount output.iso and verify its file listing. Test bootability in a virtual machine when that matters. For exact preservation of a non-optical disk or removable-media image, keep the original .img and use software that supports raw images directly.