The 49ers signed Johnson to a reserve/future contract Wednesday, Aaron Wilson of ProFootballNetwork.com reports.
Johnson spent the 2021 season on the Eagles' practice squad and was elevated to the active roster for the team's wild-card loss to Tampa Bay. He'll now attempt to secure a role with the 49ers during the offseason. Since the 25-year-old isn't on San Francisco's 53-man roster, he won't be eligible to appear in the NFC Championship Game or the Super Bowl.