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Disk image format with copy-on-write features used by QEMU virtualization.
File type: Virtual machine, virtualization software related file
The .qcow file extension represents a disk image file format primarily used by the QEMU virtualization software. It supports features like snapshots, compression, and encryption, making it a versatile choice for virtual machine storage.
File type category:
Virtual machine, virtualization software related file
Date updated: July 9, 2026
The .qcow (QEMU Copy-On-Write) format is a disk image format developed for use with QEMU, an open-source machine emulator and virtualization tool. It was later succeeded and replaced by .qcow2, which offers enhanced features. Despite this, some legacy systems and tools still utilize or recognize the original .qcow format.
The format supports advanced features such as snapshotting, thin provisioning, compression, and encryption, enabling efficient management of virtual machine storage. .qcow images are flexible and can grow dynamically, reserving space on disk as data is written, which optimizes storage utilization. Technical details include a header with metadata, optional backing files, and a flexible data layout to support various features.
Multiple virtualization platforms and tools, primarily QEMU, can open and operate with .qcow files on Windows, macOS, and Linux systems. It remains relevant in environments that utilize QEMU-based virtualizations, particularly in cloud computing, development, and testing scenarios.
To open and use .qcow files, you should install QEMU, which is available for Windows, macOS, and Linux. Using the included QEMU utilities, you can create, modify, and run virtual machines that utilize .qcow images. GUI front-ends like Virt-Manager on Linux or specific virtualization tools on Windows can also manage these files seamlessly.
Ensure the correct version of QEMU is installed to support .qcow files, and load the images via the dedicated commands or interfaces provided by these tools.
Converting .qcow files to other formats can be achieved with QEMU's 'qemu-img' command-line utility. For example, to convert a .qcow image to a raw disk image, you can run qemu-img convert -f qcow -O raw source.qcow target.img. Similarly, converting from other formats to .qcow requires specifying the appropriate input and output options.
There are also various third-party tools and online services that can facilitate format conversion, although using qemu-img remains the most reliable method. Always ensure to back up your data before performing conversions to prevent data loss.
Software applications that can open qcow files:
Microsoft Windows
Linux/Unix
Software apps that create qcow files:
Microsoft Windows
Software applications that handle other tasks involving qcow files:
Microsoft Windows
Linux/Unix
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