This ligand enables high-contrast imaging of diverse tau fibrils characteristic of both Alzheimer’s disease (AD) and non-AD tauopathies, including three repeat (3R) tau fibrils exemplified by PiD and four repeat (4R) tau fibrils observed in corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.