org.apache.hc.core5.http.io.entity.HttpEntityWrapper responsible for handling deflate Content Coded responses. In RFC2616 terms, deflate means a zlib stream as defined in RFC1950. Some server implementations have misinterpreted RFC2616 to mean that a deflate stream as defined in RFC1951 should be used (or maybe they did that since that's how IE behaves?). It's confusing that deflate in HTTP 1.1 means zlib streams rather than deflate streams. We handle both types in here, since that's what is seen on the internet. Moral - prefer gzip!