.qcow2

What is a .qcow2 file?

QCOW2 is QEMU/KVM's native disk format — supporting snapshots, compression, and encryption for Linux virtualisation.

Safe format
Type System
By Fabrice Bellard (QEMU project)
MIME application/x-qemu-disk

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What is it

QCOW2 is the native disk format for QEMU and KVM — the virtualisation stack that powers most Linux cloud infrastructure. AWS, Google Cloud, and countless hosting providers run KVM under the hood, making QCOW2 one of the most widely used virtual disk formats in production, even though most users never see it.

The format's copy-on-write design means snapshots are nearly instant — creating a snapshot just starts recording changes from that point, without copying the entire disk. QCOW2 also supports transparent compression (zlib or zstd), AES encryption, and backing files (a snapshot chain where each file stores only its differences from the parent).

QEMU and virt-manager are the standard tools on Linux. `qemu-img` creates and converts QCOW2 images. For cross-platform use, convert to VMDK (VMware) or VDI (VirtualBox) with `qemu-img convert`. The format isn't supported natively on Windows or Mac but can be used through QEMU's cross-platform builds.

Technical details
Full Name
QEMU Copy-on-Write Disk
MIME Type
application/x-qemu-disk
Developer
Fabrice Bellard (QEMU project)
Magic Bytes
51 46 49 FB
Safety
.qcow2 is a known, safe format. Virtual disk image. Contains a complete filesystem.
What opens it
QEMU / KVM
FREE Linux
virt-manager
FREE Linux
FAQ
What's the advantage of QCOW2 over raw disk images?
QCOW2 supports snapshots, compression, encryption, thin provisioning, and backing files. Raw images are faster for I/O but lack all these features. QCOW2 is the right choice unless you need maximum disk performance.
Can I convert QCOW2 to VMDK?
Yes: `qemu-img convert -O vmdk input.qcow2 output.vmdk`. QEMU's qemu-img tool converts between all major virtual disk formats.
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