Terms were not disclosed, but sources said the deal is for five years and $42 million with $26 million guaranteed.
The Browns have five days to match. They are expected to do so.
The contract has some unique elements -- most notably that Mack can void the final three years with the promise he will not receive the team's franchise or transition tag. So if Mack is unhappy after two years and wants out, he can void the deal.
The deal also includes a no-trade provision.
Mack would make $10 million this season, then $8 million in each of the next four seasons. The first three seasons, all $26 million worth, are guaranteed, meaning Mack has received the highest guarantee of any free agent this offseason.