ESPN first reported the news
The news comes a week after NFL Network Insider Ian Rapoport reported sides weren't close on a contract extension.
After trading a third and a conditional 2021 fifth-rounder to the New York Jets for a player who was on an expiring contract, Big Blue general manager Dave Gettleman repeatedly defended his decision. Monday's move to franchise tag Williams doubles down once again.
In the eight-game look-see with the Giants, Williams earned 26 tackles, half a sack and two passes defended.
Throughout his career, the former first-round pick hasn't produced massive figures as an interior defender but was still expected to have a hefty market if he reached free agency. The Giants will pay big bucks to see if a full year of Williams wearing blue can change the dynamics.
Sides have until July 15 to attempt to work out a long-term deal.