what are you looking to do? I don’t know of any consumer bank APIs but most equity and exchange brokerages will let you check account balances and make trades with an API key and credentials. Probably not initiate payments or transfers though. There are too many security risks involved for allowing that via a consumer-level API. There are also tools like Mint that store your credentials and can presumably access your data because they have corporate level agreements with the Financial institutions - I haven’t used that and would not normally recommend a corporate-based solution like that personally, but it might work for your needs.