A suction nozzle for a vacuum cleaner has: a suction mouth which can be arranged adjacently to the surface to be cleaned and which comprises a suction edge that delimits a sub-surface exposed to the vacuum air stream; a vacuum air stream extraction opening; and a delimiter that can be controlled according to a detection result of a sensor. The sensor is an obstacle sensor for detecting a substantially stationary obstacle located in front of the suction nozzle, in particular a wall or piece of furniture, wherein the obstacle sensor is configured to detect obstacles that are disposed outside the portion of the surface over which the suction nozzle projects and, in relation to an arrangement of the suction nozzle during typical cleaning operation, that protrude beyond a suction edge plane that has the suction edge.