Open Banking is a series of reforms that means all UK-regulated banks will have to let you share your financial data such as your spending habits, regular payments and companies you use with authorised providers offering budgeting apps, or other banks, via an Application Programming Interface (API) – as long as you give your permission.

API's will appear to you as a redirect from the third-party app (like Lumio) where you'll go to your banking app or banking website, it will ask if you want to allow the app access to your finances and share your data for the next 3 months, and once you say yes, you'll get redirected back to to the third-party app.  

It doesn't change or allow unlimited access to your actual account, and you can stop access at any time from your banking app. You'll get prompted every 3 months to reconnect, so you can never accidentally leave the connection running.