6-FAM-PEG3-Azide is a fluorescent dye and click chemistry reagent utilized for labeling oligonucleotides [1]. It features an azide group that participates in copper-catalyzed azide-alkyne cycloaddition (CuAAc) with alkyne-bearing molecules. Furthermore, it is capable of engaging in strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing DBCO or BCN groups.