ZIP is a well-known compression format, and has the advantage that practically anybody can open it.

However, it doesn't offer the best compression ratio. The main reason seems to be that each file is compressed individually. For example, if a 1 MB file compresses to 0.5 MB, 10 identical copies of this file will use 5 MB - similarities between the different files compressed don't help. To a lesser degree, a single file can also be made slightly smaller with programs like WinRAR.

WinRAR and WinACE offer a "Solid" mode - if this is selected, files are compressed as a group, not individually, to solve the problem named above.

The total size for a group of files (my project) is typically 30% less than the equivalent ZIP-file.

The CAB format, on the other hand, uses this by default - and the format, as such, seems to be free. It is included in some compression programs, like PowerArchiver (freeware up to version 6). The compression ratio is similar to RAR (slightly less, I would say), but not all programs that compress to CAB are very efficient.

So, as I see it, the best option (to combine a free format with a relatively good compression ratio) seems to be the CAB format. Is anybody aware of a better alternative, for distributing compressed files?

Hilmar.