Free online ISO to VDI converter

VirtualBox uses VDI files as virtual hard disks, while operating-system downloads usually arrive as ISO installation media. To run that media in a virtual machine, attach the ISO to a newly created VDI and install the system; converting the ISO's bytes directly usually does not create a usable installed disk.

What the ISO format is

An ISO file is a sector-by-sector image of optical media such as a CD or DVD. ISO 9660, UDF, and boot-image structures may be present, depending on how the disc was created. Linux and Windows installers, disc-authoring software, backup utilities, and dd commonly create or use ISO files.

An ISO normally represents read-only installation or data media. It contains the disc's files and boot information, but not the writable partition table and installed filesystem structure expected on a virtual hard disk. A data ISO can be mounted in a virtual machine for reading, but it cannot install an operating system unless it contains bootable installation media.

What the VDI format is

VDI, or VirtualBox Disk Image, is Oracle VirtualBox's native virtual hard-disk format. It provides virtual disk sectors on which a guest operating system can create a partition table, filesystems, boot files, and user data.

When creating a VDI in VirtualBox, you can choose a dynamically allocated disk, which grows as data is written, or a fixed-size disk, which reserves its configured capacity immediately. VirtualBox can attach VDIs to virtual machines, take snapshots, and manage their virtual storage. A VDI is suitable for an installed guest system; an ISO remains suitable as removable virtual optical media.

How to create a VDI from an ISO

For an operating-system installer, use VirtualBox to create the disk and install the system from the ISO:

1. Open VirtualBox and select New.
2. Choose the guest operating-system type and version, then assign memory and processors.
3. Select Create a virtual hard disk now, choose VDI (VirtualBox Disk Image), and select Dynamically allocated or Fixed size.
4. Set a capacity large enough for the operating system, applications, updates, and user data. The host must have enough free storage for the disk as it grows or for its complete fixed allocation.
5. Open the VM's Settings → Storage, select the optical-drive entry, and attach the ISO.
6. Start the VM and install the operating system onto the empty VDI.
7. After installation, detach the ISO in Settings → Storage so the VM boots from the VDI rather than restarting the installer.

This is an installation workflow rather than a sector-for-sector ISO conversion. The installer creates the partition table, filesystem, bootloader, and operating-system files that make the VDI a usable virtual hard disk. You can also attach the ISO directly whenever you only need to inspect or read its contents.

VirtualBox's command-line tool can create the same type of disk:

VBoxManage createvm --name "Test VM" --ostype Linux_64 --register
VBoxManage modifyvm "Test VM" --memory 4096 --cpus 2
VBoxManage createmedium disk --filename "Test VM.vdi" --size 40960 --format VDI
VBoxManage storagectl "Test VM" --name SATA --add sata --controller IntelAhci
VBoxManage storageattach "Test VM" --storagectl SATA --port 0 --device 0 --type hdd --medium "Test VM.vdi"
VBoxManage storageattach "Test VM" --storagectl SATA --port 1 --device 0 --type dvddrive --medium installer.iso
VBoxManage startvm "Test VM" --type gui

Adjust --ostype, memory, processor count, disk capacity, controller, and firmware settings for the guest. A VM created in the graphical interface avoids command-line configuration errors and automatically supplies many compatible defaults.

For an existing installed system stored as a raw disk image, convert the raw disk image rather than an ISO:

VBoxManage convertfromraw source.img destination.vdi --format VDI

This command is appropriate when source.img contains a hard-disk layout with partitions and an installed system. Applying it to an installer ISO only copies optical-disc sectors into a VDI; it generally does not produce a bootable installed disk and does not replace the VirtualBox installation process.

For a direct file conversion without installing desktop software, you can use the ISO-to-VDI converter on 101convert.com for free. A directly converted VDI may preserve the source image's sectors without creating the partition and filesystem layout expected by a guest, so test it in VirtualBox and use the installation workflow for bootable operating-system media.

Compatibility and limitations

Enable EFI in Settings → System → Motherboard when the installer requires UEFI; otherwise use the firmware mode expected by the source media. The VDI must be large enough for the guest's partition scheme and data, and a dynamically allocated disk still consumes host storage as it expands.

VirtualBox Guest Additions, virtual hardware drivers, and boot configuration affect performance and compatibility after installation. A physical Windows installation converted into a VDI can request reactivation and may fail to boot when its original storage controller, firmware mode, or hardware drivers change. Back up the source before converting or booting an existing system image.