Where can I find a legit VIN decoder?

I don't know if Dodge, RAM or MOPAR have their own decoder, but I can't find it if they do. Every other one that I've tried is wrong. They'll either state that my rig is SRW or a 2500; stuff like that. Is there a Chrysler certified decoder out there or at least an after market one that worth a damn? Someone suggest me a free look up VIN number on this page another one was carfax. Which one is reliable to searching VIN?