The notion of user experience (UX) and user interface (UI) is defined differently across the design industry.

Ketchup bottles

In 2019, like many others, I simplified the distinction between UX and UI by using the classic ketchup bottle analogy. At that time, as the sole designer among 90 developers and testers in an IT company - their first design hire in 35 years - I possessed strong technical proficiency but lacked deeper philosophical understanding of my role.

Throughout my early 5 years of career, the definition of UX/UI remained a significant challenge. Despite completing several online courses, I struggled to articulate comprehensive answers beyond surface-level explanations. While I could deliver effective designs, I found myself unable to confidently explain my accountability when questioned by colleagues.

UX and UI inherently coexist

Several years later, I reached a pivotal understanding: attempting to separate UX and UI was fundamentally flawed, as they inherently coexist in both digital and physical product domains. When developing user experience - although 'developing' might better describe this process than 'designing' - professionals must consider interface design, and vice versa. Interface design inherently shapes the user experience.

A well-cut diamond

During my discovery phase in 2022, I realised that the ketchup bottle analogy was insufficient for explaining the UX/UI relationship, as it suggested these elements existed in separate silos. Instead, I began conceptualising digital product design as a multifaceted diamond. Like a well-cut diamond's higher value, superior design elevates a product's worth. However, this analogy still implied distinct territories for UX and UI, albeit with shared edges and connections.

The highest and lowest

By 2025, after extensive experience and reflection on this perennial question, I achieved a clearer understanding. I now view UX/UI as a continuous stream within product design. User experience establishes the fundamental quality baseline - the minimum criteria for effective product design. Conversely, user interface design shapes and elevates the product's maximum potential, often evolving through multiple iterations driven by factors such as MVP requirements, design trends, and branding considerations.

This refined definition resonates more deeply with my understanding of product design. It acknowledges the inseparable nature of UX and UI while recognising their distinct yet complementary roles in creating successful digital products.