William George Frederik Jansen was born in Harlingen on Christmas Day 1871. He studied at the Industrial Arts School in Haarlem intending to become a machinist, but decided at 21 years to pursue a career as artist instead. He would live and work throughout the Netherlands: in Haarlem from 1902-03, then the Hague, Amsterdam and Blaricum.
Initially he was a decorative painter, he would eventually turn to painting and work on paper: etching, lithography, and drawing. His images were usually of landscapes, beach scenes and cityscapes in the manner of the Hague School painters he admired.
He would become a member of the Arti et Amicitae in Amsterdam and the Hague Art Society. Jansen exhibited officially in Rotterdam in 1902 and in Amsterdam the following year. One of his paintings is part of the permanent collection at the Rijksmuseum in Amsterdam.