Please raise a request form here: https://www.itbit.com/api or write an email to firstname.lastname@example.org. Please note that you can only get connected to our Trading & Market Data API if you have a verified Paxos account.
For API documentation:
FIX API: Financial protocol built around FIX 4.2 connectivity. Our FIX API is best for institutions and high frequency traders. FIX API documentation can be found at https://api.itbit.com/fix
REST API: HTTP-based API which offers full trading functionality for algorithmic and other active digital asset traders. REST API documentation can be found at https://api.itbit.com/docs
Market Data: HTTP-based API which provides access to itBit's order books, pricing data and trade data. Market Data API documentation can be found at https://api.itbit.com/docs#market-data