This protocol is for the generation of amplified, indexed libraries needed for downstream target enrichment and sequencing on Illumina next-generation sequencing (NGS) systems. This Twist Library Preparation Kit provides the reagents needed to prepare genomic DNA (gDNA) libraries using mechanically fragmented gDNA with either the Twist Universal Adapter System or the Twist HT (High-Throughput) Universal Adapter System. The Twist Universal Adapter System consists of Twist Universal Adapters and Twist Unique Dual Indexed (UDI) Primers, whereas the Twist HT Universal Adapter System includes Twist Universal Adapters and HT UDI Primers. This library preparation protocol is optimized for use with Twist Target Enrichment Kits and should only be performed with reagents specified or their equivalents.