Zopfli is a compression library that achieves higher compression density while
taking longer to compress. The smaller compressed size allows for better space
utilization, faster data transmission, and lower web page load latencies.
Furthermore, the smaller compressed size has additional benefits in mobile use,
such as lower data transfer fees and reduced battery use. The higher data
density is achieved by using more exhaustive compression techniques, which make
the compression a lot slower, but do not affect the decompression speed.

Zopfli is bit-stream compatible with compression used in gzip, Zip, PNG, HTTP
requests, and others.

WWW: https://github.com/google/zopfli