Ask HN: Is there any US bank with a sandbox or API?

perhaps this http://www.programmableweb.com/api/capital-one

Nope, up until earlier this year I worked in the 'innovation lab' of a top 3 US bank, that was supposedly leading in the banking API space (one of current hottest payment companies uses our backend/wholesale services) and we only offer APIs to big customers and not public, let alone a sandbox environment. My impression with all the regulatory and compliance issues it will take a long time (if ever) that banks will release such tools publicly. By that time hopefully someone will figure out a better system to bypass altogether...

EDIT: Yes, there are aggregators who have agreements with banks, but I believe the OP asked for directly accessing a bank's API, which I believe is not possible with the exception of some beta programs here and there that gives access to some non trivial bank data.

Capital One provides this toy API: http://api.reimaginebanking.com

If you want to create an app or startup that does anything involving banking, look elsewhere. The chances you will get approval from banks and regulators are zero. To have a halfway decent shot, you would need years, significant industry connections, expensive lawyers on retainer in New York and Washington, and the ability to prove you have cash on hand in the high 7 figures.

Here's a good example of what I'm talking about: https://medium.com/@oscargodson/thatll-do-pig-that-ll-do-899...

While I would expect we will see every bank releasing APIs sooner or later (http://www.theregister.co.uk/2016/02/10/consumer_trust_centr... shows the UK heading this way already), you may find it easier to work through an aggregator (plaid, yodlee, quovo, etc) initially for consumer-facing experiences.

Other commenters point out that some US banks have shared some early APIs, but most are not for public consumption and are limited to "partners". I suspect we'll see some restrictions on API access for a while still while regulators and banks get comfortable with an API approach.

Citi has had a Mobile Challenge for a few years with some API test access (http://www.citimobilechallenge.com/), and the Open Bank Project has a sandbox (https://openbankproject.com/) for their version of banking APIs.

But for now, unless you want to leverage aggregators, I think you'll need to just keep reaching out to the banks to be included as a "partner" and try to get early access, or wait til they open broadly, and I wouldn't expect to see that til the next few years for most large banks.