Williams was elevated to the Panthers' active roster Tuesday, Mike Kaye of The Charlotte Observer reports.
The Bills signed Williams to a one-year contract Thursday, Alaina Getzenberg of ESPN.com reports.
Williams finished the regular season with 33 tackles (13 solo), including one sack, in 16 games.
Williams (knee) does not carry an injury designation into Sunday's game versus the Falcons.
WIlliams suffered a knee injury during Sunday's game against the Chargers.
Williams recorded 2.5 sacks among five total tackles in Sunday's Week 15 win over Arizona.
Williams recorded four tackles (two solo) and two sacks in Sunday's 10-9 loss to Baltimore.
Williams (elbow) re-signed with Denver via a one-year contract Friday, Zac Stevens of TheDNVR.com reports.
Williams has been placed on the Broncos' injured reserve, Aric DiLalla of the team's official website reports.
Williams (knee) is active for Sunday's game against the Chargers, Aric DiLalla of the Broncos' official site reports.