Cy5 hydrazide is widely used in biochemical and biomedical research for labeling biomolecules, particularly in fluorescence-based applications. It is commonly employed to conjugate with aldehydes and ketones, making it useful for tagging carbohydrates, glycoproteins, and other carbonyl-containing compounds. This dye is extensively utilized in fluorescence microscopy, flow cytometry, and in vivo imaging due to its near-infrared emission, which minimizes background interference and enhances sensitivity. Additionally, Cy5 hydrazide is applied in the development of diagnostic assays, such as ELISA, and in studying molecular interactions through fluorescence resonance energy transfer (FRET). Its stability and bright fluorescence make it a valuable tool for tracking and visualizing biological processes in real-time.