This R package wraps htslib, and can be built from a Makefile that will pull the latest htslib source and reconstruct the R package. The package bundles htslib, and adds a few additional utilities for working with VCF/BCF and SAM/BAM/CRAM data. In particular, the package can extract genotypes and parse INFO fields from VCF/BCF files, and can calculate depths and extract sequences from SAM/BAM/CRAM files. Where possible, this package attempts to take advantage of the file agnostic API available in htslib/hts.h.