Senior Frontend Engineer

Location: Greater London

LSEG (London Stock Exchange Group) is more than a diversified global financial markets infrastructure and data business. We are dedicated, open-access partners with a dedication to excellence in delivering the services our customers expect from us. With extensive experience, deep knowledge and worldwide presence across financial markets, we enable businesses and economies around the world to fund innovation, manage risk and create jobs.

It’s how we’ve contributed to supporting the financial stability and growth of communities and economies globally for more than 300 years. Through a comprehensive suite of trusted financial market infrastructure services – and our open-access model – we provide the flexibility, stability and trust that enable our customers to pursue their ambitions with confidence and clarity.

LSEG is headquartered in the United Kingdom, with significant operations in 65 countries across EMEA, North America, Latin America and Asia Pacific. We employ 25,000 people globally, more than half located in Asia Pacific. LSEG’s ticker symbol is LSEG.OUR PEOPLE:

People are at the heart of what we do and drive the success of our business. Our values of Integrity, Partnership, Excellence and Change shape how we think, how we do things and how we help our people fulfil their potential. We embrace diversity and actively seek to attract individuals with unique backgrounds and perspectives. We break down barriers and encourage teamwork, enabling innovation and rapid development of solutions that make a difference.

Our workplace generates an enriching and rewarding experience for our people and customers alike. Our vision is to build an inclusive culture in which everyone feels encouraged to fulfil their potential.

We know that real personal growth cannot be achieved by simply climbing a career ladder – which is why we encourage and enable a wealth of avenues and interesting opportunities for everyone to broaden and deepen their skills and expertise. As a global organisation spanning 65 countries and one rooted in a culture of growth, opportunity, diversity and innovation, LSEG is a place where everyone can grow, develop and fulfil your potential with meaningful careers.

ROLE PROFILE:

We are seeking a Senior Frontend Developer to join our Customers Identity & Access Management team  will play a pivotal role in maintaining and evolving our JavaScript SDK, a critical interface that enables secure authentication and seamless integration of our Authentication into client applications across to our customers.

This role is ideal for someone who thrives in developer experience, SDK design, and security-focused frontend engineering.

What You’ll be doing:
* Own and maintain a JavaScript SDK built with React and Type Script, enabling secure integration with our custom Secure Token Service.
* Design intuitive, developer-friendly APIs that abstract complex authentication flows (OAuth2, OpenID Connect).
* Ensure the SDK is secure, performant, and easy to integrate across a wide range of frontend applications.
* Collaborate with backend engineers to align SDK functionality with evolving identity protocols and token flows.
* Build automated tests and CI pipelines to ensure quality, reliability, and backward compatibility.
* Write clear documentation and sample apps to support internal and external developers.
* Stay current with frontend security best practices and contribute to platform-wide improvements.

What You'll bring:
* Proven of experience in frontend development, with deep expertise in React, Type Script, and modern JavaScript.
* Proven experience designing and maintaining SDKs or libraries used by other developers.
* Strong understanding of OAuth2, OpenID Connect, and secure authentication flows.
* Familiarity with CI/CD pipelines, automated testing, and versioning strategies for SDKs.
* Experience with frontend performance optimization, cross-browser compatibility, and accessibility standards.
* Passion for clean code, automation, and continuous improvement.
* Excellent interpersonal skills and a passion for developer experience and security.

ROLE PROFILE:  We are seeking a Senior Frontend Developer to join our…