PKZIP is an archiving tool originally written by the late Phil Katz, and marketed by his company PKWARE, Inc. PKZIP is an acronym for Phil Katz's ZIP program.

The first version of PKZIP appeared in 1989. It was a DOS command-line tool and was distributed as shareware with a $25 registration fee. PKZIP 1 used three different compression algorithms, colourfully referred to as "shrinking", "reducing" and "imploding" which were chosen between based on the characteristics of the file being compressed. Although popular at the time, files in PKZIP 1 format are now rare, and many modern unzip tools are unable to handle the PKZIP 1 compression methods.

Some years later, PKWARE brought out PKZIP 2. This new version dispensed with the miscellaneous compression methods of PKZIP 1 and replaced them with a single new compression method which Katz called "deflating". The resulting file format has since become ubiquitous on Microsoft Windows and on the Internet - almost all files with the .zip extension are in PKZIP 2 format, and utilities to read and write these files are available on all common platforms.

PKWARE has continued to develop PKZIP, but the newer versions of the PKZIP format involve proprietary compression techniques.

In the meantime PKWARE is the world leader for compression software on the Mainframe Platform.

Also PKWARE introduced in 2004 a new Productline which is called SecureZIP, this is PKZIP + Encryption up to 256 Bit following the AES Standard. The unique thing on SecurZIP is that the whole datablock is encrypted not only secured by an password and you have also the possibility to use x.504 Certificates.

See also

• List of file archivers
• Comparison of file archivers

External links

• PKZIP server page from PKWARE