4-(9H-Carbazol-3-ylamino)phenol is a versatile dye extensively utilized across various domains. This compound is crucial in biological experiments where it enables the observation and analysis of cell structures, tracking of biomolecules, assessment of cell functions, differentiation of cell types, detection of biomolecules, examination of tissue pathology, and monitoring of microorganisms. Its applications span from fundamental scientific research to a wide spectrum of clinical diagnostics. Beyond biomedical applications, this dye finds significant use in traditional sectors like textile dyeing and in innovative areas including functional textile processing, food pigments, and dye-sensitized solar cells.