proxy.gzip.contenttype configures which responses should be compressed.

By default, responses sent to the client are not compressed even if the client accepts compressed responses by setting the ‘Accept-Encoding: gzip’ header. By setting this value responses are compressed if the Content-Type header of the response matches and the response is not already compressed. The list of compressable content types is defined as a regular expression. The regular expression must follow the rules outlined in

A typical example is

proxy.gzip.contenttype = ^(text/.*|application/(javascript|json|font-woff|xml)|.*\+(json|xml))(;.*)?$

The default is

proxy.gzip.contenttype =