QCOW File

What are QCOW files and how to open them

Are you having problems opening a QCOW file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your QCOW files.

What is a QCOW file?

QCOW files have multiple uses, and QCOW Disk Image is one of them. Read more about the other uses further down the page.

QCOW Disk Image

The QCOW Disk Image (.QCOW) format is a virtual disk image used by QEMU virtualization software. It stores the contents of a virtual machine's hard drive in a way that uses disk space more efficiently than raw images. QCOW implements copy-on-write: when a virtual disk based on an existing image ("backing file") is modified, only the changed parts are stored in the QCOW file rather than copying the entire original. This lets QCOW images start small and grow only as data is written.

QCOW files can support backing files, meaning the image can depend on another file for unchanged data. They offer optional compression using zlib, and optional encryption using AES in CBC mode. These features allow compact storage and some protection of data at rest but are considered weaker or deprecated compared to more modern formats. Typical workflows include creating, converting, and using QCOW images via QEMU tools such as "qemu-img", and they are mainly used internally by QEMU when compatibility with older versions or simpler feature sets is required.

Internally QCOW version 1 files start with a 32-bit magic number 0x514649FB ("QFI\xFB") at offset 0, followed by a version field set to 1. Key header fields include version, backing_file_offset and size, cluster_bits, encryption method (AES or none), and table offsets that map guest blocks to host storage clusters.

How to open QCOW files

We have identified one QCOW opener that is compatible with this specific type of QCOW file.

Programs that open QCOW Disk Image files

Last updated: August 10, 2026

All known file formats using extension .QCOW

While QCOW Disk Image is a popular type of QCOW-file, we know of 2 different uses of the .QCOW file extension. Different software may use files with the same extension for different types of data.

QCOW1 Disk Image

We know that one QCOW format is QCOW1 Disk Image. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

While we have not verified the apps ourselves yet, our users have suggested two different QCOW openers which you will find listed below.

Various apps that use files with this extension

These apps are known to open certain types of QCOW files. Remember, different programs may use QCOW files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about QCOW file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.