This info was reported late last week, by Matt Maiocco of the Press Democrat. It is now official:

The San Francisco 49ers signed free agent safety Chad Williams on Wednesday to a contract. Terms of the deal were not released.

Williams began his career with the Baltimore Ravens as a sixth-round selection in the 2002 draft. He played in 64 games with the Ravens, making five starts, and registered 158 tackles, eight interceptions, three forced fumbles and 5.5 sacks.

The 5-foot-9, 207-pound safety also has three defensive touchdowns, including a 98-yard interception return for a score. Williams also spent time on Baltimore’s special teams.