GZIP Compression Methods

The standard compression method is DEFLATE, a combination of LZ77 succeeded by entropy coding. Therefore a Huffman code is applied. Although the specification provides a corresponding header field, only the DEFLATE algorithm is specified for the time being.

The DEFLATE algorithm described in RFC 1951 is not restricted by patents as far as known. To ensure its free usage Jean-loup Gailly had investigated a large number of patents before starting developement. DEFLATE is also used for the ZIP format of PKWARE but the surrounding file structure and other compression methods of ZIP are incompatible.

DEFLATE []

Compression rates achievable with GZIP are comparable with ZIP varying due to different algorithms, parameter sets and applications used. The more complex BZIP2 and 7z algorithms also developed as open source projects provide a clearly better compression.