Compression Methods

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 Zip 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.

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.

SuperFast

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.

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).

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).

LZMA

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

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).

XZ

XZ is an open-source data compression method that makes use of the LZMA2 algorithm to produce a higher compression ratio.** **

Jpeg compression

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 **

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".

**MP3 compression **

The MP3 compression is designed to compress MP3 audio files. For these files, it will generally produce better compression than other compression methods supported by WinZip.

	MP3 compression cannot be manually selected. Instead, WinZip will automatically use it when appropriate if you choose "Best method".

What is the difference between "Legacy" and "Best method" compression?

WinZip applications, which create Zip files (.zip or .zipx), allow you to choose between two different compression methods. The Legacy method creates Zip files that are compatible with almost every other Zip file utility, but the compression used is not likely to create the smallest Zip files possible. The Best method alternative uses compression that will create smaller Zip files (usually) with a .zipx extension, but this method will not be compatible with all Zip file utilities.

.Zip Legacy compression (maximum compatibility)

The Legacy (Zip 2.0) compression method, which creates .zip files, uses a traditional data compression algorithm, known as deflate. Deflate is supported by all versions of WinZip and virtually all other Zip file utilities. The deflate method is generally considered to be a good, all-purpose compression algorithm for use with most types of files. .Zip: Legacy compression is your best choice if you will be sharing your Zip file, especially if you do not know what Zip file utility the receiver of your shared files will use or if you already know that an older or limited utility will be used. WinZip applications use the highest deflate method setting available, which is maximum deflate. Using WinZip, your .zip files will be easily unzipped and they will be as small as possible for this compression method.

.Zipx Best method (smallest size)

The Best method option allows WinZip applications to choose a compression method from those available in the application for each file. The choice is based on the file type and is usually the method that will compress that type of file the most. .Zipx: Best method should be selected if compressed file size is a primary concern. If you plan to share a .zipx file, please make sure that the receiver of your shared file is using the latest version of WinZip or another Zip file utility that is compatible with all of WinZip's advanced compression methods.

Increased Control - WinZip ribbon compression options

The WinZip ribbon provides another level of control. In the Settings tab, you can choose a different compression method for WinZip to use when creating .zip and/or .zipx files. These compression method settings will by saved when you close WinZip so that you will not have to make the change again. If you want to use a different method later, you can change settings again.

If you have any questions about this information, please submit a Technical Support ticket.

Compiled from the official WinZip Knowledge Base (https://kb.winzip.com/)