What is a .cab file?
Windows Cabinet · Archive · Microsoft · 1990s
A CAB (cabinet) file is Microsoft's compressed archive, used to bundle files for Windows installers, drivers and updates. You rarely open one by hand: Windows setup and driver tools read it, but 7-Zip can extract one if you need to.
What is a .cab file used for?
A .cab packs multiple files with good compression, and it is the container Windows uses inside setup programs, driver packages and system updates.
Because installers and INF-driven driver setups consume it automatically, you seldom open a CAB directly. When you do need the files, 7-Zip or the built-in expand command extracts them.
It is purely an archive, so like a ZIP it holds files but runs nothing on its own.
What opens a .cab file?
The .cab format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- File Explorer (view)
- 7-Zip
- expand command
macOS
- The Unarchiver
- 7-Zip
Linux
- cabextract
- 7-Zip
Web
- Not natively; extract locally
Open a .cab file step by step
- Confirm the file really is a .cab. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with File Explorer (view) or 7-Zip.
- On Mac, use The Unarchiver or 7-Zip.
- On Linux, try cabextract or 7-Zip.
- Still stuck? Convert the .cab to ZIP, which opens more widely.
Why can't I open my .cab file?
Almost always because no installed app understands CAB. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .cab at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .cab file
You can convert a .cab file to ZIP, 7Z using a conversion tool or the export menu of an app that opens it.
What is the .cab file signature (magic bytes)?
A .cab file starts with the hex bytes 4D 53 43 46, which read as MSCF in ASCII. Programs identify CAB by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for CAB. For a full breakdown, see the Cabinet (CAB) file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| 4D 53 43 46 | 0 | MSCF | 'MSCF' |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .cab file?
A CAB (cabinet) file is Microsoft's compressed archive, used to bundle files for Windows installers, drivers and updates. You rarely open one by hand: Windows setup and driver tools read it, but 7-Zip can extract one if you need to.
How do I open a CAB file?
Double-click to browse it in File Explorer, or extract it with 7-Zip. From a command prompt, expand file.cab -F:* target-folder pulls the files out.
How do I extract a driver from a CAB?
Extract the CAB with 7-Zip or the expand command, then point Device Manager's Update Driver, Browse my computer at the extracted folder so it can find the .inf file.
Related formats
Sources
Details on this page were checked against authoritative references. How sources are ranked and what is deliberately left out is set out in the methodology.