Qcow image format

QEMU files to store a disk image.

MIME types

File signature

QCOW files start with hexadecimal: 0x51 0x46 0x49 0xfb (ASCII: "QFI.")

File types

Currently there are three versions of the QCOW1 format; namely QCOW (version 1) and QCOW2 (version 2). Version 3 is considered an extended variant of QCOW2.

Contents

The QCOW format is used to store storage media data, e.g. disk images.

The QCOW image file consists of:

• the file header
• the L1 table (cluster aligned)
• the reference count table (cluster aligned)
• reference count blocks
• snapshot headers (8-byte aligned on cluster boundary)
• clusters containing:
• L2 tables
• storage media data

The clusters are 512 bytes of size

Encryption

The QCOW2 format supports optional AES encryption

See Also

• Disk Images

External Links

• The QCOW Image Format, by Mark McLoughlin, June 2006
• The QCOW2 Image Format, by Mark McLoughlin, September 2008
• QEMU Copy-On-Write file format, by the libqcow project, December 2010

Tools

• libqcow
• QCOW Data Recovery - Recover data from corrupt or crashed QCOW, QCOW2 virtual image files.