QCOW2 files save disk images in QEMU’s second Copy on Write format version. This format allows smaller file sizes. It delays storage allocation until needed disk space. Other formats often allocate fixed space amounts. Some is unused then. NOTE: QEMU still mounts both QCOW2 and original QCOW images.
You can mount QCOW2 images. Use them to create virtual machines in QEMU and some other programs. QEMU also creates and modifies QCOW2 files. See its documentation.
QEMU developed QCOW2. It saves virtual machine hard drive contents. Similar to QCOW extension using original format. Features different snapshot storage strategy. Allows smaller sizes delaying allocation until needed.
Windows: Right click QCOW2 file. Click “Open with” and “Choose another app”. Select program. Check box to always use it.
Mac: Right click QCOW2 file. Click “Open with” and “Other…”. Choose program. Check “Always Open With” box.
Linux: Right click file. Select “Open with”. Choose program.
iPhone: Tap the file.
QCOW2 stores disk images. It supports AES encryption and zlib compression. Often has virtual machine hard disk data. Succeeds QCOW files still supported by QEMU.
One QCOW2 file software: QEMU. It is a Disk Image Format.
QCOW2 has Low Popularity. Not on most devices. That covers main details.
QEMU
VirtualBox
Virt-Manager