Magnetic domain structures and their evolution in quasi-two-dimensional ferromagnet Cr5Te8

•Magnetic domain dynamics of quasi-two-dimensional ferromagnet Cr5Te8.•Domain structure observation by microscopic magneto-optical Kerr effect technique.•Cr5Te8 domains evolve dendritically with characteristic angles either 60° or 120°.•Close relation between domain structure and in-plane arrangement of Cr atoms.•Disrupted domain growth by surface defects.