What is a .qcow2 file?
QEMU Copy-On-Write v2 · Disk image · QEMU project · 2004
QCOW2 is the native disk image format of QEMU and KVM, the Linux virtualisation stack. It supports snapshots, compression and thin provisioning, only using disk space as data is actually written.
What is a .qcow2 file used for?
A .qcow2 file starts with the magic QFI followed by 0xFB. Copy-on-write means the image grows on demand and can layer snapshots, so you can roll a VM back to an earlier state cheaply.
It is the default for KVM-based clouds and Linux virtualisation. Manage and convert it with qemu-img.
How to open a .qcow2 file
The .qcow2 format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .qcow2 file.
Windows
- qemu
- qemu-img
macOS
- qemu
- qemu-img
Linux
- QEMU / KVM
- qemu-img
- virt-manager
How to convert a .qcow2 file
You can convert a .qcow2 file to vmdk, vhd, img using a conversion tool or the export menu of an app that opens it.
.qcow2 file signature (magic bytes)
Programs recognise a .qcow2 file by the bytes at the start of the file, not by its name. These are the signatures for QCOW2. For a full breakdown, see the QCOW2 file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| 51 46 49 FB | 0 | 'QFI' + 0xFB |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .qcow2 file?
QCOW2 is the native disk image format of QEMU and KVM, the Linux virtualisation stack. It supports snapshots, compression and thin provisioning, only using disk space as data is actually written.
How do I open a qcow2 file?
Boot it with QEMU or virt-manager, or convert and inspect it with qemu-img. It is a virtual disk image for QEMU/KVM.
What are qcow2 snapshots?
Copy-on-write points in time you can return to. Because only changed blocks are stored, snapshots are cheap in space and fast to create.
How do I convert qcow2 to another format?
Use qemu-img convert, for example qemu-img convert -O vmdk disk.qcow2 disk.vmdk for VMware.
Related formats
Sources
Details on this page were checked against authoritative references: