Zopfli: New compression library from Google

With Zopfli, Google has introduced a new, C-based compression library as open source software. Named after a Swiss pastry, its algorithm is said to produce results that are 3 to 8 per cent more compact when compressing web content than the popular zlib library at maximum compression level. These results have been documented by Google. Like zlib, Zopfli is an implementation of the Deflate algorithm that is also used in the zip file format and in PNG files, but it appears to result in smaller output files.

Zopfli is compatible with the popular browsers' decompression algorithms. Zopfli's compression results are equal to that of gzip, but the library appears to be more effective at compressing data. Google said that it hopes that the traffic reductions that are caused by the new library will increase data transmission speeds and lead to shorter loading times when displaying web pages. The smaller compressed size will particularly benefit mobile applications, Google added, as it will incur lower data transfer fees and reduce battery usage. However, at maximum compression level, Zopfli requires two to three orders of magnitude more CPU time than zlib to perform the actual compression.

The new algorithm was developed by Zurich-based Google engineer Lode Vandevenne as part of a "20 per cent time" project. Google allows its developers to spend one fifth of their work time on their own developments. Zopfli is now available to download and has been released under the Apache 2.0 licence.

Correction: An earlier version of the article was corrected to accurately reflect the increase in CPU time when compressing at Zopfli's maximum compression setting.

(sno)