Free online QCOW to VDI converter

Source format

QCOW is a QEMU Copy On Write disk image format used mainly with the QEMU emulator and virtualization stack. It stores a virtual hard drive in a file and supports features such as copy-on-write, snapshots, and sparse allocation. QCOW is commonly used by developers, testers, and system administrators who run Linux or other operating systems in virtual machines.

In practice, you may see QCOW or the more common QCOW2 variant. Both are virtual disk images, but QCOW2 is the modern format and is used far more often today.

Target format

VDI is the VirtualBox Disk Image format used by Oracle VM VirtualBox. It is the native virtual disk format for VirtualBox and is designed for use with VirtualBox virtual machines. VDI supports dynamically allocated disks and can be convenient when you want to move a VM disk into a VirtualBox-based environment.

The main advantage of VDI is direct compatibility with VirtualBox. If your goal is to boot or attach the disk in VirtualBox, converting to VDI can simplify setup and improve integration with that platform.

How to perform the conversion

The most reliable method is to use VirtualBox or qemu-img. If you already have VirtualBox installed, you can convert the disk with its built-in disk utility. If you prefer a command-line approach, qemu-img is usually the best tool.

Method 1: using qemu-img

1. Install QEMU tools if they are not already available.
2. Open a terminal or command prompt.
3. Run a conversion command such as qemu-img convert -O vdi source.qcow2 target.vdi.
4. Wait for the process to finish, then attach target.vdi to a VirtualBox VM.

If your source file uses the older QCOW format, the command is the same; just replace the filename with your QCOW image, for example qemu-img convert -O vdi source.qcow target.vdi.

Method 2: using VirtualBox

1. Open VirtualBox.
2. Go to File → Virtual Media Manager.
3. Select the source disk image if it is already recognized, or use the command-line tool that ships with VirtualBox to clone/convert the disk.
4. Choose VDI as the output format and save the new image.

For many users, the command-line qemu-img method is simpler and more predictable, especially when converting between different virtualization platforms.

You can also convert the file on 101convert.com for free, without installing any software.

Notes on quality and compatibility

This conversion is usually lossless because it converts a virtual disk image rather than re-encoding media. The file contents should remain the same, but the resulting image may differ in metadata, allocation method, or snapshot support.

Keep in mind that QCOW snapshots and advanced features may not transfer cleanly into VDI. If the source image depends on a snapshot chain, merge or flatten it first before converting. Also, make sure the source image is not in use while converting, and verify that the guest operating system boots correctly after the conversion.

Finally, if the source is actually QCOW2 rather than QCOW, the same conversion approach applies. In most cases, qemu-img will handle both formats without issue.