Azido-PEG7-acid is a PROTAC linker belonging to the PEG class, used in the synthesis of PROTAC molecules. It functions as a click chemistry reagent, incorporating an Azide group that facilitates copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc) with molecules containing Alkyne groups. Additionally, it can engage in strain-promoted azide-alkyne cycloaddition reactions (SPAAC) with molecules that possess DBCO or BCN groups.