Info-ZIP

An open source project that started in 1990 to create portable compressor-archiver utilities that are compatible with PKWare's PKZIP file format.

History
Info-ZIP developed two command line application programs Zip and 'Unzip that handle compression and decompression respectively. Although the Zip program can decompress as well as compress, in addition there are a few related utility programs some of them included in the main package and some available as a separate download.

The Info-Zip code has a fairly liberal licence which meant code from the project was routinely used in projects that required file compression, archival capabilities or compatibility with the ZIP file format, however in modern use it is more common to use compression libraries such as the Info-ZIP derivative Zlib unless the archival features of Info-ZIP are required, since the libraries are more flexible and give much better compression ratios.

However apart from the utility you get from the Info-ZIP Zip and Unzip programs themselves there are cases where it makes sense to use Info-Zip code in your project rather than a library or even use applications themselves and make them a dependency of your program. Some software such as Java Jars implementation understands the ZIP file format to be strictly ISO/IEC 21320-1:2015 compatible, i.e. they only allow Deflate 0 and 8 and require the file structure to be compatible with the Info-ZIP one, in those cases the more modern compression libraries have no advantage since the better compression ratios are not understood or even allowed by the ISO 21320-1 and similarly with a library you will need to write your own file structure code but all that is already built into Info-ZIP.

The project ran into a number problems during its early years, some of the core programmers wanted to extend the capabilities of the package over and above what PKZIP had to offer and align with the Free Software Foundation by releasing under the GPL, however both of these proposals were rejected by the rest of the community due to compatibility reasons and the restrictions of the GPL, this eventually lead a number of core team members to start a new project called gzip that was part of the FSF GNU project, although later projects by the same team have eskewed the FSF and been released under a more liberal licence.

Software

 * UnZip 6.0 (2009-04-29)
 * Zip 3.00 (2008-07-07)
 * WiZ 5.03 (2005-03-11)
 * MacZip 1.06 (2001-02-22)

Links

 * Info-ZIP Home Page
 * Info-ZIP technical information
 * Info-ZIP forum
 * Archive of the old Info-ZIP forum