Compression is done on the fly .
This assumes that you're really on a slow link, where you have lots of CPU, but not much bandwidth. A nifty usage for that filter, is to plug it on top of a org.w3c.jigsaw.proxy.ProxyFrame , in which case it will compress the data when it flies out of the proxy. The set of MIME types we are allowed to compress. This attribute is an editable StringArrayAttribute default value This attribute defaults to null .