7-Zip Compression

More about 7-Zip Compression and comparison of compression formats in PowerArchiver


7-Zip is the superior compression format featured in PowerArchiver. It is an open source format, providing open architecture and high compression ratio. It is also an modern format, that supports UNICODE filenames (so international users will not have any issues with special characters), maximum file sizes up to 16000000000 GB, and strong encryption (AES 256 bit). However, 7-Zip's greatest strength is that it is an open format - it is not forcefully controlled by any organization or individual, but an LGPL project that anyone can contribute to. Everyone can find and use latest DLLs and implement them into their application. This way it is impossible have a situation similar to ZIP format, where we have several different versions of ZIP files that not everyone can open in the same way, or such as with RAR, which is still not supported by some compression utilities due to its proprietary format. By its nature, everyone is encouraged to use 7-Zip in their applications with fairly liberal LGPL licensing.

Compression ratio

While most users will not understand nor care about what license a format distributed under, they will certainly care about the compression ratio that 7-Zip provides. 7-Zip mostly uses the LZMA compression method found in other formats, but with stronger compression settings and dictionary sizes which result in better (if slower) compression. 7-Zip also uses solid compression which enables a better compression ratio (same as with CAB and RAR). We have tested all formats found in PowerArchiver, as well as some other most popular formats that people use (RAR and ACE) in order to demonstrate compression strengths of 7-Zip.

Compression example

For our example of 7-Zip compression, we have compressed a Open Office 2 installation, which is a open source office suite. We have used a program installation because it is easy to show differences in compression ratios, but if you use any application you will notice similar results.

  • Installation in its original state is 202.156 kB in size and contains over 3.128 files.
  • 7-Zip at Ultra settings had 13% better compression ratio than WinRar at its highest setting and 55% better compression ratio than Zip at its maximum settings. You should see even an better compression ratio as the size of the files that you are compressing goes up, or less as it goes down (but even with smaller files, you should save 10% compared to RAR at its maximum settings).
  • 7-Zip compression is at its best when used to compress applications (binary data), although it is still good for text compression when using special PPMD setting.
  • ZIP compression - while 7-Zip in this case provides 55% better compression than ZIP, we still recommend use of the ZIP format for most daily tasks, since its speed/compression ratio is still the best.
  • 7-Zip at Normal setting was able to compress installation 18% better than WinZip 11's Optimize for maximum compression setting, which is incompatible with any other archiver on the market, including WinZip 10. Not only that, but in this test, 7-Zip Normal compression was also quicker than WinZip's.
  • PowerArchiver's ZIP compression is better than WinZip 11 ZIP compression in this case, when comparing standardized ZIP format that can be read by hundreds of millions of computers around the world, including every computer with Windows XP and Vista installed (which do not support WinZip's own extensions to ZIP format).

Things to know about 7-Zip (and its shortcomings)

  • Due to its strong compression settings, 7-Zip at Ultra setting will take up a large amount of memory - 369 MB (34 MB for decompression)! If you use 7-Zip's Maximum compression setting, memory usage will go down to 84 MB (10 MB for decompression) and if you use Normal setting, 7-Zip will use 27 MB of your memory and need only 4 MB for decompression.
  • From PowerArchiver 2007, we have added transparent updating of 7-Zip archives, which enables you to update 7-Zip archives, something that was not possible before. You can set it up in our Configuration> Miscellaneous options window.

Find out more about 7-Zip

7-Zip has been created by Igor Pavlov and is distributed under the LGPL. You can find out more about the 7-Zip format here. You can contribute to the 7-Zip open source project at Source Forge's 7-Zip project page.