unikmer is a golang package and a toolkit for nucleic acid k-mer analysis, providing functions including set operation k-mers (sketch) optional with TaxIds but without count information. K-mers are either encoded (k<=32) or hashed (arbitrary k) into uint64, and serialized in binary file with extension .unik. TaxIds can be assigned when counting k-mers from genome sequences, and LCA (Lowest Common Ancestor) is computed during set opertions including computing union, intersecton, set difference, unique and repeated k-mers. WWW: https://github.com/shenwei356/unikmer