Ranger has joined Southend United on a one-year-contract, with the option of a further year.
The 25-year-old former Newcastle, Swindon and Blackpool forward has been training with the League One side during pre-season.
He has not played a competitive game since November 2014, before he spent seven months absent from Blackpool.
Southend boss Phil Brown told the club website: "There's two or three reasons why we've chosen to extend Nile's deal.
"First and foremost there is a footballer in there which we identified at the start and that's the reason he came through the door on trial.
"Secondly we have a contract that safeguards us as a football club, but also safeguards Nile if he keeps his nose clean and performs well on the pitch.
"But the bottom line is, he's come in as an option up front which is totally different from what we've got at this moment in time in terms of playing style."