Choosing a Compression Method
WinZip® provides several methods for compressing the files that you add to a Zip file. In making a choice of compression methods, there are several things to consider, including the type of data you are compressing, your plans for later unzipping the data, and the amount of time you are willing to wait while your data is being compressed.
Using the WinZip Ribbon Interface
In the WinZip Ribbon Interface, you will need to select the appropriate compression method to use prior to beginning the zipping process.
Setting the compression method is accomplished on the Settings tab of the WinZip Ribbon. Set the appropriate compression method in the .Zip and .Zipx fields to use when creating .zip or .zipx files, respectively.
For more detailed information on each of the compression methods, see the Additional information on specific compression methods section below.
Using the Legacy Toolbar interface
In most cases, WinZip provides three basic choices for compression method in the Add window when you add files to a new or existing Zip file:
- .Zip: 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.
- .Zipx: 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. Choosing Best method will result in a .zipx file; so if you are planning to share these Zip files with others, you should be sure that they are using WinZip 12.1 or later. The Jpeg compression and WavPack compression methods are only available when using Best method.
- Let me choose the specific compression method: if you choose this option, you can select a specific compression method from a list that includes No Compression, SuperFast, Enhanced Deflate, bzip2, LZMA, and PPMd. Choosing bzip2, LZMA, or PPMd will result in the creation of a WinZip 12.1 (or later) compatible .zipx file.
Additional information on specific compression methods
Here is additional information for all of the compression methods supported by the current version of WinZip:
None or No compression
Some files that you may want to add to a Zip file are already compressed. For example, many multimedia and sound files, such as avi 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 None or No compression when you are adding a group of files that are already compressed.
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, SuperFast, and Normal. These all used the same basic technology but were optimized in different ways for speed vs. compression. WinZip 12 and later no longer uses Fast and Normal when compressing files, but it can still extract files compressed with any of these methods.
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).
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).
LZMA is an open-source data compression method that uses a dictionary compression scheme that uses a larger dictionary size than the deflate method. It can produce a higher compression ratio than older methods.
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).
The Jpeg compression method is designed to compress JPEG images. JPEG images are inherently hard to compress because their format already incorporates a simple but effective compression scheme. At a high-level, Jpeg compression works by first undoing the lossless compression (entropy encoding) within JPEG images and then recompressing them with a better algorithm. When the image is uncompressed, the reverse happens—the Jpeg compression algorithm is undone and the original JPEG entropy encoding is reapplied.
|Jpeg compression cannot be manually selected. Instead, WinZip will automatically use it when appropriate if you choose "Best method".|
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 method".|