So… what is the difference between them? And why is it important to understand this difference?

Interface Design, or UI

Focuses on the artifact, or in other words, what is on the screen. When designing interfaces, the problem being solved is within the design: selecting and arranging interface elements (e.g., text and form fields), design consistency (with the platform, with other screens), etc.

It’s important to clarify that Interface Design is not the same as Graphic Design: interface design may or may not include graphic design. For example, when creating a wireframe, one is designing an interface but not applying graphic design, whereas applying style rules to an interface involves graphic design but not interface design.

User Experience, or UX

Focuses on the user and the experience to be achieved. UX refers to what the user experiences before, during, and after interacting with the artifact.

Without incorporating the user, UX cannot be done. Therefore, it is essential in experience design to first understand the users and their true motivations and needs, consider what interface, content, and interactions will achieve the desired result from that perspective, and finally, validate with users the results produced by the proposed interface.

Validation can be done directly (user testing, qualitative interviews, mental model surveys) or indirectly (heat maps, A/B testing, click maps).

The difference between direct and indirect validation is not only methodological. Direct validation is usually qualitative, meaning it helps us understand why users do what they do, while indirect validation shows what they do but doesn’t explain why. Therefore, it is good to first validate the experience qualitatively as a “rough adjustment,” and then quantitatively for “fine-tuning.”

Interaction Design, or IxD

Involves defining how the interface operates (e.g., whether information input or selection occurs via keyboard, mouse, touch, or a combination of these), operational flows, and system responses. Ultimately, it focuses on the interaction between the user and the artifact.

Why is it important to understand the difference between UI, UX, and IxD?

Returning to the initial question, there are two answers:

  • On one hand, to communicate clearly what we are doing and the scope we are addressing.
  • On the other hand, to generate a common language with those making requests. If everyone understands that Interface Design (UI) does not necessarily imply User Experience (UX), we might be fortunate enough to avoid requests to “add UX to the screen”; and if we are not so fortunate, we will at least know how to ask the necessary questions to understand exactly what is being asked and help to reformulate the request based on the actual need.