Harris didn't receive a qualifying offer from the Bruins, and he'll become an unrestricted free agent Wednesday, Belle Fraser of the Bruins' official site reports.
Harris made eight regular-season appearances for the Bruins last year, recording a goal, two assists, five hits and five blocked shots while averaging 15:54 of ice time. He's made NHL appearances in each of the last five seasons, and it wouldn't be surprising to see him generate interest on the open market during the offseason.