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Choosing a Compression Method

In most cases, WinZip provides three basic choices for compression method:

• Legacy compression: This method, referred to as Maximum Deflate in earlier versions of WinZip, provides good, fast compression that is compatible with virtually all Zip file utilities. You may want to choose this option if speed of compression is a primary concern, or if you are sending the Zip file to others who may not have a Zip file utility that can extract files compressed with newer methods.
• Optimize for maximum compression (sometimes called "Best Method"): This choice allows WinZip to choose the best compression method for each file, based on the file type. You may want to choose this option if compressed file size is a primary concern. If you are planning to share the Zip file with others, you should be sure that they are using WinZip 11.0 or another Zip file utility that is compatible with all of WinZip 11.0's compression methods.
• Let me choose: If you choose this option you can select a specific compression method from a list that includes None, SuperFast, Enhanced Deflate, bzip2, and PPMd. Information on these methods is below.

Here is a list of all compression methods supported by WinZip 11.0:

None or No compression

Some files that you may want to add to a Zip file are already compressed. For example, many graphics and sound files, including JPG, GIF and MP3 files, are precompressed versions of images and sound. In most cases, these types of files cannot be further compressed to any significant degree by the available methods. Therefore, to save time, it may be best to select Let me choose and then pick None when you are adding a group of files that are already compressed.

Compatibility: Virtually all Zip file utilities are able to extract uncompressed files.

SuperFast compression

This is a good, general-purpose compression algorithm known as "deflate". It is the same basic algorithm as is used for Legacy compression (see above), but is optimized for speed rather than compressed size. Therefore it will generally compress your files somewhat faster than Legacy, but the compressed files will be somewhat larger.

Earlier versions of WinZip supported four variants of the deflate algorithm, referred to as Maximum (portable), Fast, Super Fast, and Normal. These all used the same basic technology but were optimized in different ways for speed vs. compression. WinZip 11.0 no longer uses Fast and Normal when compressing files, but it can of course extract files compressed with any of these methods.

Compatibility: All versions of WinZip and almost all other Zip file utilities are able to extract files compressed using these methods.

Enhanced deflate

The "enhanced deflate" method is similar to the original deflate but operates on larger chunks of data at a time, often resulting in improved compression. It can be particularly useful for compressing large files containing large amounts of highly compressible data such as large text files and text-based database files.

Earlier versions of WinZip referred to this compression method as Maximum (enhanced deflate).

Compatibility: Versions of WinZip prior to WinZip 8.1, and some third-party Zip utilities, may not be able to extract files compressed with this method. Therefore, if your Zip file is intended for wide distribution, and you cannot be sure what Zip utility will be used, you might want to consider using SuperFast compression instead.

bzip2

bzip2 is an open-source data compression algorithm that compresses most files more effectively than the traditional deflate methods, but it can be somewhat slower.

Earlier versions of WinZip referred to this compression method as Maximum (bzip2).

Compatibility: Files compressed using the bzip2 method can be extracted from Zip files with WinZip versions 9.0 and higher, as well as a few other Zip utilities. Therefore, the bzip2 method should only be used when the means for unzipping is assured.

PPMd

PPMd is an open-source data compression algorithm that can compress most text-based data more effectively than either the traditional deflate or bzip2 methods, but which is quite often slower than either.

Earlier versions of WinZip referred to this compression method as Maximum (PPMd).

Compatibility: PPMd compression was introduced in WinZip 10.0 in November, 2005. Extracting files created with this compression method requires a compatible Zip file utility. Because we have published implementation details on the WinZip web site, we expect this feature to be adopted by other Zip file utilities over time.

WAVPACK

WAVPACK is an open-source compression method that is especially designed for lossless compression of .WAV (audio) files. For these files it will generally produce better compression than other compression methods supported by WinZip.

WAVPACK compression cannot be manually selected. Instead, WinZip will automatically use it when appropriate if you choose "Best compression".

Compatibility: WAVPACK compression was introduced to the Zip file format in WinZip 11.0. At the time of this writing (November, 2006), WinZip is the only Zip file utility with the ability to extract files compressed with WAVPACK. However, as we have published implementation details on the WinZip web site, we expect this feature to be adopted by other Zip file utilities over time.