Since his father was the senior physician of a ward in the Bad Schussenried Centre for Psychiatry, he grew up with his three siblings in a service flat on the former hospital grounds. He attended the Studienkolleg St.Johann Blönried and graduated from there in 2003. At the age of 17, he lived for one year on the Pine Ridge Indian Reservation, where he graduated from Red Cloud High School in 2001. In 2008 he completed his acting education at the Otto Falckenberg School in Munich.
He studied at the Hochschule für Fernsehen und Film München and graduated there in March 2018 with a diploma in documentary film directing and television journalism.
Internationally, Kranz was seen in the drama The White Ribbon (2009) by Michael Haneke, in Quentin Tarantino's war film Inglourious Basterds and in Steven Spielberg's Bridge of Spies. He became known to a wider television audience with the series Hindafing, in which he plays the city priest Kraus. The series was awarded the Austrian film prize Romy in 2018.
His spot myBorder's joyFence was awarded the First Steps Award and the Porsche Award in 2018.