Q. Now, what is the best compression program?.
A. That depends on your definition of 'best'. Globally speaking there are three kind of compressors / archivers.

First we have the group of experimental compressors, designed with only one thing in mind, getting the best possible compression regardless the time it takes and the amount of memory it uses. Almost all programs in this group are command line (dos/win32) programs, and some of them can only compress one file at a time (remember user friendliness wasn't a real consideration). The best programs in this group, i.e. the ones getting the best possible compression, are WinRK (using PWCM mode), PAQ8, PAQAR, Durilca and SLIM. At the moment WinRK (PWCM) and PAQ8 are the two best compressors of the five, but they are also much slower then Durilca and SLIM (to give you an idea; PAQAR in -8 mode does about 5-7 KB/s on a slightly overclocked AMD Barton 2800+). If you have files with embedded images (e.g. Word DOC files) use PAQ8, it will recognize them and separately compress them, boosting compression significantly. Also note all mentioned programs with the exception of WinRK are free of cost.

Secondly we have a group which tries to combine the good compression of group one with some degree of user friendliness. Compression is still very good, speed is reasonable, but the compression formats used are often not widely spread. Best programs is this group are UHarc (with WinUHA gui) and WinRK.

The last group is the 'everyday use' archiver. This are GUI driven programs with good compression, but without sacrificing speed and without excessive memory usage like the group 1 and 2 programs. Apart from the GUI it is important the program is fast, easy to use, and supports many different archive formats (or is a standard itself). The best archivers in this group are WinRar and 7-Zip. Maybe WinZip 10 (using PPMd-mode) has a place here too.

Q. Why didn't you include program xxxxx ?
A. I try to keep the comparison benchmarks fair and transparent by only listing one single version of a program (the one with the best compression). For that reason I don't include clones of a program (like PAQ clones WinUDA, Emilcont and KGB), 'light' versions (like Durilca Light) and programs without an own compression format (like PowerArchiver, Total Commander, ZipGenius, TUGzip). If you still think I missed a program please let me know!. You can mail me (Werner Bergmans) at 'info _AT sign_ thissitename dot com' (or have a look at the front page to see this email address spelled out...). PS. Most of these clones and light versions are included in the multiple file compression (MFC) test.

Q. Why don't you add compression times?
A. As the sites' name already indicates, I'm looking for the maximum compression ratio. The time it takes is irrelevant (to me), getting the best switch combinations takes by far the most time... I agree time is useful to know if you are considering an 'every day use' compressor, but that's not what the site is about.

Apart from the fact it takes a lot of time to do all measurements there is a bigger problem. I try to find the best combination of switches to yield maximum compression (and this really can be an exotic combination for programs like 7-Zip, Durilca etc). That particular combination can lead to say 40.00% compression with a compression speed of say 20 Kb/s. A different set of switches can have 39.99% compression with a speed of 500 Kb/s. Is it fair to list this 20 Kb/s as, 99.9% of the people will not use the switches I used?. I think speed comparisions are only fair if you let the program use it's default settings. The multiple file compression test (MFC) does include (de)compression times are more 'regular' switches / options are used there.