Introduction

7-Zip is an open source file archiver, similar to WinRAR or WinZip. Its name comes from the 7z file format, which 7-Zip was one of the first to implement. It is one of the few complete and free file archivers for Windows.

7z

7z files have a very high compression ratio. Tests on 7-Zip’s website claim a 30-70% smaller file size compared to other formats. In compressing files for my own use, I've found that 7z does do a better job than zip or rar. In a test I compressed a demo, something Gotfrag is full of. Demos compress very well, and showed the difference between zip, rar, and 7z clearly.

The difference is 3mb between 7z and the other formats. This adds up and could save a lot of bandwith for the website.

There are hundreds of different compression formats, but zip, rar, and 7z are the best examples of formats that balance speed and compression. Tests done by http://www.maximumcompression.com/ show that there are some compressors that take much more time, but compress the files better. On their tests, the best compressor took a 310mb folder filled with various kinds of files down to 62mb, but it took 8 hours.

An advantage of using 7z is that you have the option of packing a self extractor when you compress it. This turns the compressed file into an executable, so people don't need 7-Zip installed to unpack 7z files. I should mention two things with this though. One is that WinRAR has support for 7z files, and that even though the file is an exe you can still open it like any other compressed file.

A less talked about advantage is that 7z is open and modular. The default compression method, LZMA is where 7z gets its namesake. There are also can use other methods such as bzip2 and ppmd. But they have no advantage over LZMA, and 7z and LZMA are usually thought of as one in the same.

I find 7z is commonly used with Oblivion mods, since they contain a wide variety of files and 7z can compress them into small file sizes. This saves bandwidth for users who wish to distribute their mods.