UI design (User Interface design) is the design discipline concerned with the visual and interactive elements of digital products — the buttons, typography, colour schemes, spacing, icons, forms, and graphical components that users interact with. Where UX design defines how a digital experience should work and flow, UI design defines how it looks and feels. Good UI design combines aesthetic appeal with clarity — every visual decision serves a functional purpose (this button looks clickable because it needs to be clicked; this section is visually distinct because it contains the most important information).
In practice, UI design and UX design are deeply intertwined. A beautiful UI built on a poor UX structure will frustrate users regardless of how attractive it looks. A sound UX structure with poor UI will feel rough and untrustworthy despite being functionally logical. The best digital products are the result of integrated UX and UI design — structural thinking and visual execution working together toward the same goals.
Core UI design principles
- Visual hierarchy — using size, weight, colour, and placement to guide the eye toward the most important elements first
- Consistency — using the same visual patterns for the same types of elements (all primary buttons look identical, all headings follow the same rules)
- Contrast — sufficient colour contrast between text and background for readability; minimum 4.5:1 ratio for normal text per WCAG AA accessibility standards
- Whitespace — generous spacing around elements reduces cognitive load and improves comprehension
- Affordance — design elements should visually signal their function; buttons should look clickable, links should look like links, form fields should look enterable
- Feedback — interactive elements should visually confirm they have been activated (hover states, loading indicators, success messages)
- Responsive design — UI must adapt appropriately across desktop, tablet, and mobile screen sizes
Figma is the industry-standard UI design tool in 2026, used by the majority of professional design teams globally. It allows collaborative design, prototyping, and component library management in one browser-based tool. Adobe XD and Sketch are alternatives, though Figma has become dominant. For designers coming from a print background, Adobe InDesign and Illustrator are not well-suited to UI design. For businesses commissioning UI design work, Figma files are the standard deliverable format — they allow you to inspect and extract design specifications without needing design skills.
At smaller scale — individual website projects, app MVP design — a single designer with UX and UI skills (often called a 'product designer') handles both. At enterprise scale — large product teams with complex interfaces — dedicated UX researchers, UX designers, and UI designers are separate specialisms. For most UK SMEs commissioning a website or marketing tool, a design agency or freelancer who describes their work as 'UX/UI design' will handle the integrated process. What matters is that your designer thinks about both how the interface works (UX) and how it looks (UI) — not just the latter.