The move clears about $6.3 million from Washington's salary cap. The Redskins would like to re-sign left tackle Trent Williams, outside linebacker Ryan Kerrigan, and running back Alfred Morris, all of whom have been chosen for Pro Bowls and whose contracts expire after this season.
Chester, 32, signed with Washington in 2011. He had worked with the starters during Tuesday's first practice of organized team activities.
Porter, 28, signed with Washington in 2014 but played in just three games because of shoulder and hamstring injuries. He was absent because of flight complications according to coach Jay Gruden.