AF 430 is a coumarin dye with absorption maximum at 430 nm and emission in green-yellow range (maximum at 542 nm). The dye is one of few fluorophores that absorb in the range between UV-excited fluorophores (e.g. DAPI with an excitation peak at 358 nm, AMCA/AMCA-X at ~350 nm) and fluorescein (maximum at 494 nm). It is a photostable and hydrophilic dye - trifluoromethyl group in its structure reduces photobleaching while sulfo group provides better hydrophilicity and higher quantum yield in aqueous solution. Its fluorescence is independent of pH over a wide range of pH values (from pH 4 to pH 10) and can be excited by 405 nm violet laser.

AF 430 possesses a large Stokes shift of 112 nm which makes the dye valuable for multi-color imaging applications, including wide-field and confocal fluorescence microscopy, STED microscopy, and flow cytometry. Fluorophores with large Stokes shift allow reducing cross-talk and the number of excitation/detection channels.

As the dye exhibits high photostability, it is suitable for STED microscopy where enormous light intensities are used. AF 430 is applied in multicolor STED microscopy by combining two dyes — one with a large and one with a small Stokes shift. Depletion of both dyes can be performed with one wavelength (AF 430 can be depleted by 660 nm laser).

Due to its specific spectral properties, AF 430 is often used in FRET experiments both in material and life sciences.