Article

Behind the Numbers: Open banking APIs and the Infrastructure of Financial Innovation

24 September 2025

Author: Irin Rahman, Head of Data, Open Banking Limited

What you’ll learn in this article:

  • Every API call represents real impact – whether it’s a service delivered, a decision made, or a customer served, the billions of monthly connections show open banking is working reliably and at scale.
  • Open banking is thriving – these milestones aren’t just numbers; they’re proof of a functioning, mature ecosystem that’s quietly transforming financial services.
  • The UK is leading the digital revolution – as open finance and smart data evolve, the UK stands out not just as a participant, but as a global leader in digital innovation.

Often when using a third party’s app to pay for bills or switching services seamlessly, a quiet, shared infrastructure is at work: open banking APIs.

In July, Open Banking Limited (OBL) recorded two major milestones: more than 2 billion API calls in a single month and 15 million active users* across the UK. These numbers don’t just speak to technical capacity – they highlight how deeply open banking has become part of the UK’s financial and digital landscape.

2 Billion API Calls: A Signal of Scale and Trust

API traffic is more than a metric – it’s a reflection of how much real economic activity is being powered by open banking. Two billion calls in a single month demonstrate scale, reliability, and resilience.

Importantly, this growth is accelerating. Year-on-year traffic rose 36% to July 2025, compared with 22% in the same period two years earlier. What was once an innovation project is now a core part of national infrastructure; underpinning services relied upon by millions daily.

15 Million Users*: Mainstream Adoption

This API growth has been accompanied by a continued increase in user connections; reaching 15 million of whom marks a clear shift from early adoption into the mainstream. That’s almost one in three UK adults who are now actively using open banking services – whether they realise it or not.

The growth is not evenly distributed. Payment initiation (PIS) has grown to consistently outpace account information (AIS). Five years ago, AIS accounted for three-quarters of all users; today, PIS represents 55% of the base. The July figures reinforce this trend, with PIS volumes growing 10.5% month-on-month compared with 3% for AIS.

This shift matters because it shows open banking is not only a tool for data aggregation but also for frictionless, secure payments at scale.

What’s an API-and Why Should You Care?

An API, or Application Programming Interface, is a set of rules that lets different software systems talk to each other. It’s like a translator that allows apps, websites, and services to exchange information securely and efficiently.

In open banking, APIs are the technology that makes everything work behind the scenes. They allow your financial apps to access your bank data (with your permission), initiate payments, verify your identity, and much more – all without manual input or paperwork.

Why is this important?

  • APIs make open banking possible. Every time you use a budgeting app, switch energy providers, or get a loan quote based on your actual spending, an API is doing the heavy lifting.
  • The volume of API calls shows real-world usage. In July alone, over 2 billion API calls were made – each one representing a moment of connection, a service delivered, or a decision made.
  • High API usage signals a healthy ecosystem. It means more businesses are building on open banking, more consumers are benefiting, and innovation is accelerating.

In short, APIs are the infrastructure of open banking. You don’t see them – but they’re powering the future of finance.

Beyond Finance: The Wider Impact

While banks and fintechs are the most visible adopters, the potential for open banking APIs stretches across industries:

  • Energy: Smart billing, affordability checks, and new consumer tools are being powered by open banking data.
  • Utilities: Seamless account switching is reducing friction for households and businesses.
  • Identity services: Secure, real-time ID verification is reducing fraud and simplifying on boarding across sectors.

These cross-sector applications demonstrate how open banking is laying the foundations for open finance and smart data ecosystems, where secure data sharing supports innovation in everything from mortgages to insurance.

What’s Next?

As we celebrate these milestones, attention naturally turns to what comes next. Three developments stand out:

  • The Long Term Regulatory Framework for UK open banking:  This will put open banking on a more sustainable footing for the long term, essential to unlocking further innovation, expanding adoption, and ensuring that the benefits of smarter financial services reach even more people and businesses.
  • The Open Finance Roadmap: extending the principles of open banking into broader financial products, from savings to pensions.
  • The UK’s Smart Data Strategy: led by the Department for Business and Trade, which will see the infrastructure applied well beyond finance.

At OBL, our role is to ensure that growth and trust move forward in lockstep. Standards, security, and consumer control will remain the foundation as we expand into new domains.

Why This Moment Matters

Milestones are useful markers of progress, but their real significance lies in what they represent.

Two billion API calls show that the infrastructure can handle scale. Fifteen million users* show that adoption is no longer in question. The acceleration of payments initiation shows that open banking is changing consumer behaviour.

In short: open banking is not an experiment anymore – it is a pillar of the UK’s digital economy.

Final Thought

Behind every API call is a service delivered, a decision made, or a customer served. The billions of connections happening every month are not abstract data points. They are proof that open banking is working – quietly, reliably, and at scale.

And as open finance and smart data take shape, these milestones remind us that the UK is not just participating in a digital revolution. It is leading it.

Author: Irin Rahman, Head of Data, Open Banking Limited

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*Open Banking are unable to identify individuals consuming services through more than one brand.  Reporting therefore represents the number of user connections with the brands providing reporting, rather than individual users.

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