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Products » ZIP


What is ZIP? What can ZIP do for me?

ZIP files to save storage space

To put it simply, ZIP allows you to compress files to save storage space. Zipped files take up much less space on hard drives, flash drives, CDs, DVDs, etc.

ZIP files to speed transmission time

If you want to quickly send files, ZIP makes the job much easier. By compressing the file(s), sending information via email, FTP, etc. is that much easier – the smaller the file, the faster it will reach its destination.

How does ZIP work?

When a file is zipped (compressed), all redundant data is replaced by a smaller reference to that data. This allows the file to be reduced in size for easier storage and/or transfer. When that file is unzipped (decompressed), the reference is replaced by the original data so it can once again be read in its original form.

ZIP is lossless

ZIP is a “lossless” form of file compression – this means that none of the original data is ever lost.

.ZIP file format

The ZIP file format is a data compression and archive format. Individual files are compressed to reduce their size and then placed in a ZIP archive. ZIP files are usually labeled with a .zip or .ZIP file extension. ZIP is the most popular file format in the world and is utilized by individual users, businesses, and government agencies to efficiently handle and manage files. The .ZIP Application Note is available here.

Founder of ZIP

PKWARE founder, Phil Katz , invented the .zip file format in 1986. Phil made the .zip file standard an open standard in 1989.

ZIP software from PKWARE

While there are many products available today that will zip a file, PKWARE offers both PKZIP and SecureZIP software. PKZIP and SecureZIP will each compress files up to 95%! In addition to the file compression and management capabilities of PKZIP, SecureZIP offers all of the benefits of PKZIP plus strong encryption to protect sensitive information. To download a free 30-day evaluation of our ZIP products, click here.

Unzip software

After a file is zipped, it must be unzipped to access it. PKZIP and SecureZIP will both unzip as well as zip files. For those who need to unzip and/or decrypt files. but do not need to zip them, PKWARE continues to offer its ZIP Reader  for free. ZIP Reader will not zip files. To download ZIP Reader, click here.

Self-extracting ZIP files

If there is a need for a file that can be unzipped without the use of decompression software, a self-extracting zip file can be created. A self-extracting zip file will have a .exe file extension.

Application Note Archives

This page provides a fixed location for APPNOTE reference and change history.

Specific versions of the APPNOTE named within other published specifications are posted here for reference.

6.2.0 – 04/26/2004
This version is provided in support of ECMA-376 and ISO/IEC 29500, the standards for Office Open XML File Formats. These document standards incorporate ZIP technology based on this specification.

To download APPNOTE version 6.2.0, Click Here or copy and paste the following URL into your browser window:

Other Archived Versions:


Thank you for your interest in the Application Note. You will receive an email when updates are made to the Application Note.


ZIP File Format Specification Publication Policy

In order to ensure the interoperability of the .ZIP file format by third party development organizations, PKWARE® remains committed to the periodic publication of the APPNOTE specification. The publication of changes and revisions to this specification will occur on the following schedule:

Notification of Change
When feature changes affecting the .ZIP file format are identified, a preliminary release of this information will be made within 120 days following the general release of the first product in which these changes are implemented. This preliminary information will identify areas of current or planned changes to allow third party developers to avoid any conflicts with their development activities.
Final Publication
Final publication of feature changes to the specification will occur within nine months of the general release of the last product in which these changes are implemented. The availability of the final release of the specification will be timed to ensure the changes work reliably and conflict-free across all supported operating environments.
Naming Convention
The current general released version of the APPNOTE will retain the file name APPNOTE.TXT. Draft copies will be named a APPNOTE-x.y.z-DRAFT.txt. Archived copies will be named APPNOTE-x.y.z.TXT.

1 x, y, and z represent the version major, minor and step version.