Cracknell, 20, has been training with City throughout pre-season and has featured in a number of the club's friendly fixtures this summer.
The shot-stopper has penned a five-month deal with the Bantams after leaving Hull City's academy at the end of last season.
Cracknell, who featured for the Tigers in their academy and reserve fixtures throughout the 2014/2015 season, also enjoyed a spell on loan at Scarborough Athletic during the campaign.
The custodian is now expected to add competition to City's goalkeeping position as well as keep goal for City's Final Third Development League matches this year.
Discussing Cracknell's arrival at the club, Bantams boss Phil Parkinson said: "Joe has impressed us over pre-season and he has earned himself this contract.
"Hopefully he can keep improving and become a good prospect for us.
"We have been looking for a young goalkeeper for Lee Butler (goalkeeper coach) to really work with and help to develop. Joe certainly fits the bill.
"We have our under 21s competition this season and he will be figuring prominently in that."