He reportedly received a $1.3 million signing bonus.
Williams, a cornerback from Oklahoma State, was the first pick the Broncos made in this year's draft. He is expected to compete for playing time on defense and is the favorite to return kicks and punts this season.
Third-round pick Maurice Clarett remained unsigned but was at Broncos headquarters. Coach Mike Shanahan said he expected all players would be signed by the first practice.
Only Clarett and sixth-round pick Chris Myers, an offensive lineman, remained unsigned.
"This is not brain surgery," coach Mike Shanahan said. "There's a certain percentage that you pay over what you paid last year at the same slot. It's pretty easy to figure things out what a guys should get, at least within a thousand or two."
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