Implementation Guide

Getting Started

Customers who want to make use of the finX API for Financial Data are just three API calls away from getting access to the financial data of their users 

1. Create a Widget link for one-time account information access
2. Exchange an authorization code for an access token
3. Fetching the financial data 

1. Flow initiation

POST /onetime/access

{
  "redirect_uri": "https://my-app.example.com/callback",
  "language": "de",
  "accounts": [],
  "sync_period": 90
}

Please note that the redirect_uri is the only mandatory parameter as it will lead the user back to your application. All other parameters are optional, but some will have a direct effect on the user flow.

To shorten the flow for your users and achieve maximum conversion, we highly recommend to use the accounts parameter. In case the IBAN or other information (e.g. Account Number or PAN) of the users are known they can be passed on as an account id.

"accounts": [
  { "id": "DE82900948150000002881" }
]

To optimize conversion, you might consider asking the user for their account details before initiating the widget. This will allow the user to skip the bank selection screen and they will be prompted to directly authorize with their bank.

The sync_period defines the number of days of transaction history requested from the financial institution. The default value is set to 90 but can be set higher depending on the use case.

{
  "location": "https://finx.finleap.cloud/?token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJoYWhhIjoiaSBtYWRlIHlvdSBsb29rIn0.jk1WqP6S28bNuP5MwwlZHR_5GlksWsEZPMztWUAIiJY",
  "id": "3ca31c37-986a-454e-ad64-8e97143c86bc"
}

Forward the user to the location provided in the response. This can be achieved by using:

1. an overlay/popup iframe
2. a redirect in the same or a new window

2. Exchange authorization code

After a user successfully went through the flow, they are redirected to the redirect_uri provided in your initial request to create the Widget link. The following query-parameters will be automatically added by us:

1. state: The value provided by you during flow initiation. You can use this to identify which user is now being redirected to the redirect_uri and reinstantiate the state of your website accordingly.
2. success: Indicator whether or not the flow was successfully completed by the user.
3. code: The authorization code to be exchanged for an access token to gain access to the financial data of the user. It is only returned in case the user successfully went through the flow and is valid for one hour.
4. cancel: Indicator whether or not the flow was canceled by the user. Only present in case the user actually canceled the flow and not in other error cases.

https://example.com/callback?code=eyJhbGciO...&state=7fe78733&success=true

Requesting an access token

POST /auth/token

{
  "grant_type": "authorization_code",
  "code": "eyJhbGciOiJIUzI1NiIsInR5cCI6Ikp...",
  "redirect_uri": "https://my-app.example.com/callback"
}

{
  "access_token": "AoFmNJLDTW8jQtGSJ1iZeeoLiwNZ2ihz3iiCHGpuvE439nppuY...",
  "expires_in": 3600,
  "scope": "accounts=ro balance=ro transactions=ro offline",
  "token_type": "Bearer",
  "refresh_token": "RTfI2WNyK78NozupDH9ai8GPRbjjdVsXPPt..."
}

You have to provide the returned access_token in the HTTP Authorization header of subsequent API requests. In case of an ongoing use-case, you additionally need to store the returned refresh_token on your end to permanently keep access to your enduser's data. Whenever you use an existing refresh token you will automatically get a new one in the response. Your application has update it's existing one in your storage backend to ensure the token is valid and not expired. If no user activity is present within 90 days, or the refresh token is not replaced with a new one, your access will be lost.

Token lifetimes

📘

The actual length in bytes of all tokens (access and refresh tokens as well as authorization codes) can vary. Therefore it is highly advised to not limit the size of the database field in your storage backend. If you have to specify a size for the corresponding database field a choice of at least 2048 bytes is highly recommended.

3. Fetch financial data

Please view the Fetching Account & Transaction Data section for a detailed overview.