CRISPR-Cas design tools are software platforms and bioinformatics tools built to facilitate the design of guide RNAs (gRNAs) for use with the CRISPR/Cas system. CRISPR-Cas design tools are software platforms and bioinformatics tools built to facilitate the design of guide RNAs (gRNAs) for use with the CRISPR/Cas system. The CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR associated nucleases) system was originally discovered to be an acquired immune response mechanism used by archaea and bacteria. It has since been adopted for use as a tool in the genetic engineering of higher organisms.