Midfielder Jarred Moore and rookie-listed players Eugene Kruger, Jack Lynch and Dylan McNeil have also had their Swans careers ended.
Seaby's future look clouded when he failed to break back into the team after round seven.
Fellow ruckman Mike Pyke came into the team for round eight and held his place for the rest of the season.
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Seaby, 28, played five games in 2012 for a total of 18 since joining the Swans before the 2010 season.
He played 102 matches with West Coast from 2004-09.
Moore, 26, this season failed to add to his 68 games with the Swans since making his debut in 2005.
Swans general manager of football Dean Moore said: "All of these players have had a positive impact on our club and we thank them for all their hard work.
"We wish to pay special tribute to Jarred Moore, who has been an outstanding leader and popular member of the playing group.
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"His leadership and experience has been incredibly valuable to the young players in our squad.
"We wish all the players the very best for the future."
