The Wales U21 international will remain at the Liberty Stadium for the next three years.
"I'm very happy to have signed a new contract," he told Swansea's official website. "It gives me stability as I have the next three years to continue progressing here.
"It's also reassuring knowing that the club see something in me and believe that I can grow as a goalkeeper.
"But the hard work starts now for me. I want to become a bigger part of the manager's plans and I have to keep improving every day in order to do that."