“Shadowhunters” has been cancelled and will end after the second half of season 3 and a special 2-hour finale are aired. The series, made by Constantin Films, aired in America on Disney-owned cable channel Freeform but was branded as a Netflix Original around the rest of the world. The Netflix Original branding helped to foot most of the bill for the show’s production but this deal has been lost and Freeform were apparently unwilling to give the extra cash needed.
The second half of season 3 will air in Spring 2019 and then there will be a 2-hour season finale to wrap the series up.
Source: Hollywood Reporter