Azido-PEG20-Boc is a PROTAC linker within the PEG category, used in the synthesis of PROTAC molecules. It functions as a click chemistry reagent containing an azide group, enabling copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc) with alkyne-containing molecules. Additionally, it participates in strain-promoted azide-alkyne cycloaddition reactions (SPAAC) with molecules containing DBCO or BCN groups.