There has been substantial interest in the development of screening methods capable of surveying a wider sample of chemical space and larger numbers of compounds. Over the past two decades, DEL technology has evolved into a broadly utilized and validated platform in drug discovery, yielding diverse hits for a wide range of biologically relevant targets. Read the full review for a historical and technical overview of DEL technology, including how libraries are prepared and screened, a comparison to other HTS methods, and examples of successful applications in drug discovery.