What is the KZ file format?
.kz files store data of various types that have been compressed using KuaiZip software. The format is proprietary and used only by this program. KuaiZip is a Chinese freeware program for compressing and decompressing files. It claims an increase in the efficiency of data packing by 5 to 30% compared to the RAR standard and about 10% compared to 7Z. The latest version of the program was released in 2011 and is no longer being developed.
.kz files, regardless of type, are opened in the latest available version of the software. To unpack a file it is necessary to install the KuaiZip application, available for Windows only. The archives support:
- multi-volume compression
- solid-type compression
- locking and testing compressed archives
- creating a self-extracting archive
- adding and viewing comments to the archive
.kz files may be encrypted and password-protected, but recovery of a lost password is not possible.
After unpacking a .kz archive in KuaiZip, one can access the files contained within it. The software also allows recompression or archiving into common formats such as ZIP, 7Z, ACE, ARJ, BZ2, CAB, GZ, ISO, JAR, LZH, or TAR. KuaiZip also enables the mounting of archives or disk images as virtual drives.
Because the .kz format is proprietary and KuaiZip has been abandoned since 2011, these archives are a dead end - the only program that can open them is KuaiZip itself.
Security & safety
RISK: MEDIUMKuaiZip is Chinese freeware last updated ~2011. The software itself has been described in community discussions as a 'WinRAR clone' but no major malware findings are documented. However, as with any old, unmaintained freeware - especially from an unverified developer - exercise caution when installing KuaiZip on a production system. Scan both the KuaiZip installer and any .kz archives with current antivirus before use. Prefer running in a sandboxed environment.
Format details
in a nutshellPrograms that open KZ files
Windows1 app
KuaiZip
Free Open the .kz archive in KuaiZip and extract. This is the ONLY program known to support the .kz format. Download from kuaizip.com/en/download.html (last release ~2011). Technical details
deep spec| Format type | Proprietary binary compressed archive |
| Container | Proprietary KuaiZip binary archive; internal structure not publicly documented |
| Magic bytes | None publicly documented |
| Byte order | Little-endian (assumed; Windows-only software) |
| Compression algorithm | Proprietary; developer claims 5-30% better ratio than ZIP/RAR, approximately 10% better than 7Z |
| Encryption | Password protection supported; lost password cannot be recovered |
| Multi-volume support | Yes - archives can be split across multiple volumes |
| Solid archive support | Yes |
| Self-extracting archives | Supported (SFX creation) |
| Archive comments | Supported - comments can be added and viewed per archive |
| Associated OS | Windows only |
| Interoperability | KuaiZip also reads and writes ZIP, RAR, 7Z, ACE, ARJ, BZ2, CAB, GZ, ISO, JAR, LZH, TAR, and other common formats |
| Released | ~2011 (KuaiZip, latest release; exact initial release date unknown) |
| Latest version | KuaiZip as of ~2011 (no updates since; effectively abandoned) |
KZ conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about KZ files.
