Vorm landed in South Wales earlier this year after countryman Dorus de Vries quit the Championship play-off winners to join Wolves. And he has only let in two goals in six home games.
"I thought I'd a better chance there so I signed. I worked hard and was first choice at 21. After seven years I'm here."
Swans boss Brendan Rodgers said: "We needed a keeper who was comfortable with the ball at his feet.
"We like to start from the back, so he has to also be a good footballer."