For those who *must* cram their data into the smallest possible archives, paq is an archiver with the best lossless compression ratios now available across a wide variety of test data, according to several benchmarks. It uses adaptive weighting of context models to obtain archives that are typically about 65%-85% of the size of the corresponding best-performance gzip archives. This comes at the expense of increased memory usage (30MB - 1650MB, depending upon the user-specified level of compression), and lower speeds(compression and decompression are often tens of times slower than bzip2 or gzip, and can be as much as several hundreds of times slower). The command-line interface permits compression, decompression, and viewing of the contents of archives. Compression preserves directory structure but not file attributes. There are no commands to update an existing archive or to extract part of an archive. Files and archives larger than 2GB are not supported (but might work on 64-bit machines, not tested). File names with nonprintable characters are not supported (spaces are OK). Note that different versions of paq are usually incompatible, so steps must be taken to ensure that the contents of archives made with older versions of paq will still be accessible after updating paq. WWW: http://www.cs.fit.edu/~mmahoney/compression/