FLASH is a crispr-cas9 technology that enriches for targeted sequences in sequencing libraries. The initial DNA sample undergoes a blocking step that removes of the 5\u2019 phosphoryl groups of the DNA fragments, resulting in a product that is not amendable for downstream adaptor ligation or amplification via standard Illumina-based library preparation. The subsequent incorporation of targeted CRISPR-cas9 library exposes the desired regions of interest, allowing them to be processed into a library. For more information on methods and results, please see the FLASH paper. For FLASH guide RNA design help, please see our github.