 It's fundamentally the same algorithm.What has changed is the increase in dictionary size from 32 KB to 64 KB, an extension of the distance codes to 16 bits so that they may address a range of 64 KB, and the length code, which is extended to 16 bits so that it may define lengths of three to 65,538 bytes.This leads to Deflate64 having a longer compression time, and potentially a slightly higher compression ratio, than Deflate.