Starting with version 1.1, ZipIt can both compress and decompress files in PKZip 2.0 format, and is fully compatible with PKZip 2.04g, the latest version as of this writing. A new preference has been added to accommodate the new compression technique, called “deflation.” In the preferences dialog box, you may now choose to have ZipIt default to either deflation or implosion. If you choose deflation, then whenever you add a file to an archive, ZipIt will default to deflating the file, and will display “Deflated” in italics to indicate this. If you choose “Implosion”, ZipIt will use the old method. When you add a file, “Best Guess” will be in italics, indicating that ZipIt will use its best guess to choose between implosion and shrinking (in most cases, ZipIt will choose implosion). You may always change the compression method used simply by choosing the new method from the Method menu. Note that “Best Guess” now means the best PKZip 1.x-compatible compression. Deflation will always be more efficient, but will not be compatible with older versions of unzipping programs.
To summarize: If you want to create the most compatible archives possible, go to the “Preferences->Compression” dialog and choose “Default compression: Implosion.” If you want to create PKZip 2.0-compatible archives, or don’t care about compatibility but want the smallest archives, go to the “Preferences->Compression” dialog and choose “Default compression: Deflation.” You can always override the default compression by choosing a new compression method from the Method menu.
