Azido-PEG13-azide is a PEG-based PROTAC linker suited for PROTAC molecule synthesis. This compound functions as a click chemistry reagent, featuring azide groups that facilitate copper-catalyzed azide-alkyne cycloaddition reactions (CuAAC) with alkyne-containing molecules. Additionally, it engages in strain-promoted azide-alkyne cycloaddition (SPAAC) with molecules that contain DBCO or BCN groups.