Abstract: Previously compressed data is re-compressed with a better algorithm. A data analyzer analyses the compressed data to determine whether the data has been compressed with a supported compression format such as GIF, JPG or PNG. A data decompressor decompresses the data, then a data compressor re-compresses the data using the superior compression algorithm. When the data is to be reused, a data decompressor decompresses the data and a data compressor recompresses the data using the original compression algorithm. The invention may be implemented over a path in a data network. Compressed data that is to be sent over path is intercepted and re-compressed with the superior algorithm before being sent over the path. On the other end of the path, the data is converted back to its original compression format.