PKZIP 2.04g for DOS, circa 1993
PKZIP 2.04g for DOS, circa 1993
Original author(s)Phil Katz
Developer(s)PKWARE Inc
Typearchiving and data compression tool

PKZIP is a file archiving computer program, notable for introducing the popular ZIP file format. PKZIP was first introduced for MS-DOS on the IBM-PC compatible platform in 1989. Since then versions have been released for a number of other architectures and operating systems. PKZIP was originally written by Phil Katz and marketed by his company PKWARE, Inc, with both of them bearing his initials: 'PK'.


By the 1970s, file archiving programs were distributed as standard utilities with operating systems. They include the Unix utilities ar, shar, and tar. These utilities were designed to gather a number of separate files into a single archive file for easier copying and distribution. These archives could optionally be passed through a stream compressor utility, such as compress and others.

Other archivers also appeared during the 1980s, including ARC by System Enhancement Associates, Inc. (SEA), Rahul Dhesi's ZOO, Dean W. Cooper's DWC, LHarc by Haruhiko Okomura and Haruyasu Yoshizaki and ARJ which stands for "Archived by Robert Jung".

The development of PKZIP was first announced in the file SOFTDEV.DOC from within the PKPAK 3.61 package, stating it would develop a new and yet unnamed compression program. The announcement had been made following the lawsuit between SEA and PKWARE, Inc. Although SEA won the suit, it lost the compression war, as the user base migrated to PKZIP as the compressor of choice. Led by BBS sysops who refused to accept or offer files compressed as .ARC files, users began recompressing any old archives that were currently stored in .ARC format into .ZIP files.

The first version was released in 1989, as a DOS command-line tool, distributed under shareware model with a US$25 registration fee (US$47 with manual).

Version history[]



.ZIP file format[]

To help ensure the interoperability of the ZIP format, Phil Katz published the original .ZIP File Format Specification in the APPNOTE.TXT documentation file. PKWARE continued to maintain this document and periodically published updates.[19] Originally only bundled with registered versions of PKZIP, it was later available on the PKWARE site.[19]

The specification has its own version number, which does not necessarily correspond to the PKZIP version numbers, especially with PKZIP 6 or later. At various times, PKWARE adds preliminary features that allows PKZIP products to extract archives using advanced features, but PKZIP products that create such archives won't be available until the next major release.


Although popular at the time, ZIP archives using PKZIP 1.0 compression methods are now rare, and many modern unzip tools[which?] are unable to handle "shrinking" and "reducing", although "imploding" is usually supported.


Shrinking uses dynamic LZW, on which Unisys held patents. A patent for the Reduce Algorithm had also been filed on June 19, 1984, long before PKZIP was produced.[20]

Other products[]

PKWARE also used its PKZIP standards on following products:

See also[]


  1. ^ PKZIP 0.90 review (released on February 21, 1989)
  2. ^ How to Become LZW Free
  3. ^ "comp.compression Frequently Asked Questions (part 1/3)Section - [3] What is the latest PKZIP version?".
  4. ^ "Malicious Code 101 Definitions and Background". Archived from the original on March 22, 2010.
  5. ^ "A new look for an old friend: PKZip Suite 4.5". TechRepublic.
  6. ^ PKWARE Improves Efficiency and Security of Internet and Enterprise Network File Distribution
  7. ^ PKWARE Announces Security-Enabled PKZIP 5.0
  8. ^ "PKZIP Professional Edition 6.0 with Secure Desktop: Secure and compact". ZDNet.
  9. ^ Bruce Stewart (June 21, 2004). "PKWare PKZip for Windows 8.0 review - CNET". CNET. CBS Interactive.
  10. ^ PKWARE Releases New Version of PKZIP for Windows Archived October 15, 2007, at the Wayback Machine
  11. ^ PKWARE Responses to Vista Readiness
  12. ^ SecureZIP for i5/OS - FAQs
  13. ^ PKWARE Announces Free-For-Life Simplified Personal Data Security Software
  14. ^ "PKWARE SecureZIP for Windows Desktop - v11".
  15. ^ "New version of SecureZip - Security - DSLReports Forums". DSL Reports.
  16. ^ New SecureZIP for Windows Desktop Brings Public Key Cryptography to Every Type of User
  17. ^ "SecureZIP Standard Edition for Windows Desktop 12.1". PCMAG.
  18. ^ Matt Little. "Product Updates".
  19. ^ a b Buchholz, Florian. "The structure of a PKZip file". James Madison University. Archived from the original (html) on 12 April 2015. Retrieved 4 July 2019. This document describes the on-disk structure of a PKZip (Zip) file. The documentation currently only describes the file layout format and meta information but does not address the actual compression or encryption of the file data itself. This documentation also does not discuss Zip archives that span multiple files in great detail. This documentation was created using the official documentation provided by PKWare Inc.
  20. ^ "comp.compression Frequently Asked Questions (part 1/3)Section - [8] What about patents on data compression algorithms?".

External links[]