5-Ethynyl-2'-deoxyuridine (EdU), a thymidine analogue, is incorporated into cellular DNA during DNA replication and the subsequent reaction of EdU with a fluorescent azide in a “Click” reaction. EdU staining is a fast, sensitive and reproducible method to study cell proliferation[1]. 5-Ethynyl-2'-deoxyuridine is an alkyl chain-based PROTAC linker that can be used in the synthesis of PROTACs[2]. 5-Ethynyl-2'-deoxyuridine is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.