QCOW2 (QEMU Copy On Write version 2) is a disk image format used by QEMU, a popular open-source virtualization solution. It's designed to be a flexible and efficient way to store virtual machine disk images. Unlike raw disk images, QCOW2 images only allocate space on the host system as data is written to the virtual disk. This "copy-on-write" mechanism allows for smaller initial image sizes and efficient snapshotting. When a virtual machine writes to a sector on the virtual disk, the original data is preserved in a snapshot (if one exists), and the new data is written to the QCOW2 image. This allows for easy rollback to previous states. QCOW2 supports features like compression, encryption, and multiple backing files, making it a versatile choice for virtual machine storage. It is commonly used in cloud environments and by developers working with virtualized systems. The format is designed to be robust and handle large disk sizes, making it suitable for a wide range of virtual machine workloads. QCOW2 images are often used in conjunction with other virtualization technologies like KVM and Xen.