According to several recent studies, the global IP communication and digital storage have already surpassed the zettabyte threshold ($$10^{21}$$ bytes). The Internet entered the zettabyte era in which fast and secure computations are important more than ever. One solution for certain types of computations, that may offer a speedup up to several orders of magnitude, is the incremental cryptography. While the idea of incremental crypto primitives is not new, so far its potential has not been fully exploited. In this paper, we define two incremental hash functions iSHAKE128 and iSHAKE256 based on the recent NIST proposal for SHA-3 Extendable-Output Functions SHAKE128 and SHAKE256. We describe two practical implementation scenarios of the newly introduced hash functions and compare them with the already known tree-based hash scheme. We show the trends of efficiency gains as the amount of data increases in comparison to the standard tree-based incremental schemes. Our proposals iSHAKE128 and iSHAKE256 provide security against collision attacks of 128 and 256 bits, respectively.