QCOW File Extension
QEMU Copy-On-Write
- File Type qcow
- Developer David T Reynolds
- Popularity
- Application Qemu Manager
- Category Virtual Machine Files
- Format Binary
What is a QCOW file?
QEMU Copy-On-Write, identified by the QCOW extension, is a Virtual Machine Files type and includes 56 files.
With the creation of the QEMU Copy-On-Write (QCOW), David T Reynolds introduced file format along with programs built for their use.
QCOW files are supported by Windows and Linux. You can open a QCOW file using one of 2 programs, for example Qemu Manager and QEMU.
How to open a QCOW file?
The most common reason why a QCOW file cannot be opened is the absence of required software. To fix this, select a compatible program from the list. Then visit the official developer website via the provided link, download the program, and install it on your system.
The most popular programs for working with QCOW files are Qemu Manager and QEMU. To get the latest version of Qemu Manager, open the David T Reynolds website where a universal installer for all operating systems is available.
Once setup is done, your operating system should assign Qemu Manager as the default app for QCOW files.
Make Qemu Manager the default QCOW viewer
Changing the default program in Windows
- Start by right-clicking on your QCOW file and selecting the "Open With" option. From there, click "Choose another app" to continue;
- Inside the popup window, scroll through the list of applications and specifically choose Qemu Manager as the application to associate with your QCOW file;
- Check the "Always use this app" checkbox and click "OK".
Change the default app to open files on Mac
- Right click or use Control + Left Click on the desired QCOW file to access a dropdown menu of actions;
- Select "Open in application" and click "Other";
- Scroll down to the bottom of the window, where you will find the "Enable" menu. Default, "Recommended Programs" will be selected;
- In this menu, choose "All Programs" and navigate to Qemu Manager. Check the box next to "Always open in app" to make it the default program.
How to edit a QCOW file?
To edit QCOW files, you need to install specialized software that allows you not only to open but also to modify virtual machine files. Online QCOW editors usually provide fewer features than software created specifically for QEMU Copy-On-Write.
List of Top QCOW editors 2026
Following these criteria, we have put together a list of recommended QCOW editors.
| QCOW Editor Software | Developer | Platforms | Overall Rating |
|---|---|---|---|
| Qemu Manager | David T Reynolds | Windows | 4.3 out of 5 (40 reviews) |
Finding answers to QCOW file problems
If you encounter issues with QCOW files, don’t worry—most can be fixed with minor software adjustments. Refer to the troubleshooting tips below.
What are the signs that my QCOW file is damaged?
Corrupted QCOW virtual machine files may have one or more of the following symptoms:
- Poor performance when editing a file in Qemu Manager;
- Opening or processing the file in Qemu Manager or other programs causes instability or crashes in the program;
- The file shows errors when trying to open it or does not open completely;
- Unexpected expansion of the total size of the QCOW file;
- Working with the file triggers the display of error messages;
Why does Qemu Manager quit or crash unexpectedly?
Qemu Manager crashes can be attributed to outdated software. Make sure you have installed the latest updates for David T Reynolds products.
A computer restart is often the key to solving numerous common problems. That’s why, it is recommended to restart the computer before making any changes to the software settings.
What methods can be used to repair a damaged QCOW file?
Use a recovery program to open the damaged QCOW file and navigate to the "Repair" menu item. Wait for the recovery process to finish, as it will automatically repair damaged virtual machine files.