AF 555 azide is a fluorescent dye, specifically an azide derivative of AF 555. It contains an azide group, enabling it to undergo copper-catalyzed azide-alkyne cycloaddition reactions (CuAAC) with molecules that have an alkyne group. Additionally, it participates in strain-promoted azide-alkyne cycloaddition reactions (SPAAC) with molecules containing DBCO or BCN groups. Its typical excitation wavelengths are 510 nm under green laser and 610 nm under red laser.