The disclosure provides a method of labeling of cellular glycans bearing azide groups via a fluorescent labeling technique based on Cu(I)-catalyzed [3+2]cycloaddition (click activation) of a probe comprising an alkynyl group. The method entails generating a fluorescent probe from a nonfluorescent precursor, 4-ethynyl-N-ethyl-1,8-naphthalimide, by Cu(I)-catalyzed [3+2]cycloaddition of the alkyne group of the probe with an azido-modified sugar. The disclosure further provides a method of incorporating an azido-containing fucose analog into glycoconjugates via the fucose salvage pathway. The disclosure provides a method of fluorescent visualization of fucosylated cells by flow cytometry when cells treated with 6-azidofucose are labeled with the click-activated fluorogenic probe or biotinylated alkyne. A method of visualizing the intracellular localization of fucosylated glycoconjugates by fluorescence microscopy is also disclosed.