High Performance Web Sites

The Savings

Gzipping generally reduces the response size by about 70%. Table 6-2 shows examples of size reductions for scripts and stylesheets (small and large). In addition to gzip, the results for deflate are also shown.

Table 6-2. Compression sizes using gzip and deflate

File type	Uncompressed size	Gzip size	Gzip savings	Deflate size	Deflate savings
Script	3,277 bytes	1076 bytes	67%	1112 bytes	66%
Script	39,713 bytes	14,488 bytes	64%	16,583 bytes	58%
Stylesheet	968 bytes	426 bytes	56%	463 bytes	52%
Stylesheet	14,122 bytes	3,748 bytes	73%	4,665 bytes	67%

It's clear from Table 6-2 why gzip is typically the choice for compression. Gzip reduces the response by about 66% overall, while deflate reduces the response by 60%. For these files, gzip compresses ~6% more than deflate.