Article

2 Billion API calls and 15 Million users – a landmark month for open banking in the UK 

02 September 2025

Here’s what you’ll learn in this insight:

  • Open banking is now mainstream: With over 15 million UK users and 2 billion monthly API calls, it’s reshaping everyday financial interactions.
  • APIs enable secure data sharing, real-time payments, and reflect the health and growth of the open banking ecosystem.
  • User adoption and use cases are expanding: From identity verification to personalised financial advice, open banking is driving smarter, cross-sector services. Open banking is no longer a concept reserved for early adopters or fintech insiders. It’s now a part of everyday life for millions of people in the UK – whether they realise it or not. 

Author: Anton Joachim, OBL Data Scientist

Open banking is no longer a concept reserved for early adopters or fintech insiders. It’s now a part of everyday life for millions of people in the UK – whether they realise it or not.

In July 2025, the UK’s open banking ecosystem hit two major milestones: over 2 billion API calls and more than 15 million users in a single month. These figures mark a turning point – not just in scale, but in the maturity and mainstream adoption of open banking.

What Is an API – and Why Does It Matter?

An API (Application Programming Interface) is a set of rules that allows different software systems to communicate securely and efficiently. Think of it as a digital translator that enables apps, websites, and services to exchange information without manual input.

In open banking, APIs are the invisible infrastructure that powers everything; from viewing your bank accounts in one app, to verifying your identity, to making payments directly from your bank account.

Here’s why APIs are central to this transformation:

  • They enable secure data sharing and payments. With your consent, APIs allow financial apps to access your bank data and initiate transactions.
  • They reflect real-world usage. Every API call represents a service delivered, a decision made, or a moment of financial interaction.
  • They signal ecosystem health. High API volumes mean more businesses are building on open banking, and more consumers are benefiting.

A Closer Look at the Data

API Call Volumes Are Accelerating 

In the 12 months leading up to July 2025, the number of API calls made across the open banking ecosystem exceeded 22 billion—a clear sign of growing momentum. This represents a 36% increase compared to the previous year, up from 22% growth two years earlier.

About 80% of API traffic is related to Account Information Services (AIS)—such as viewing balances or transaction histories. However, Payment Initiation Services (PIS) are growing faster, with a 66% year-on-year increase.

Why the July spike? 

Seasonal activity: Summer holidays typically drive more financial interactions. 

Regulatory impact: Changes to the Online Safety Act increased demand for identity verification services. 

Unexpected payment surge: PIS calls rose by 10.5%, exceeding seasonal expectations. 

User Adoption Is Surging 

Open banking now serves 15.1 million users – nearly 1 in 3 UK adults. That’s a 34% increase in just one year.

The composition of users is also shifting. In 2021, AIS users made up 75% of the total. Today, PIS users account for 55%, reflecting growing comfort with open banking-enabled payments.

What Does This Mean for the Ecosystem? 

These milestones aren’t just technical achievements – they’re signals of a maturing ecosystem: 

For consumers: More choice, better financial control, and faster access to services. 

For fintechs and banks: A larger, more engaged user base and opportunities to innovate. 

For regulators and policymakers: Evidence of successful implementation and growing public trust. 

What’s next? 

  • Expanded use cases: From affordability checks to personalised financial advice. 
  • Smart data integration: Enabling cross-sector services in energy, telecoms, and beyond. 
  • Continued focus on security and user empowerment: Keeping consumers in control of their data and choices. 

Join the Movement 

Open banking is transforming how we manage money, make payments, and access financial services. Whether you’re a developer, policymaker, business leader, or curious consumer – there’s a role for you in this growing ecosystem.

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