User interface (UI) design is an integral part of user experience design. It has to be, right? After all, the UI is the way through which a user interacts with a device. So it’s the aim of the UI designer to improve the user’s interaction with the product, whether it’s physical or digital. 

Here you will find everything that will help you create better user interfaces and get inspired by some of the world’s leading UX and UI designers. Before we dive in, however, let’s look at a definition of ‘user interface’, the characteristics UIs need to be truly user-friendly, and the different types of UIs that will be covered on these pages. 

What is a user interface?

A user interface is the means by which a human and a computer system interact. The goal is to enable the user to operate and control the machine in order to effectively complete a task and receive feedback that makes the decision-making process easier. 

User interfaces are composed of one or more layers including a human-machine interface (HMI) using physical input devices such as keyboards, mice, and game pads as well as output hardware such as computer monitors, speakers, and printers.

UI design is closely linked to user experience (UX) design. Both are crucial for the success of a digital product, and both terms are often used interchangeably. However, they’re not the same thing. UI design is the process of creating interfaces with a focus on the surface, the looks, and style, while UX design covers the entire experience a user has with a website or app (of which the UI is just one part). 

Basic properties of user-friendly UI

To design a successful UI, it needs to have several essential characteristics. One of the most foundational components is for the UI to be functional. The design process must balance technical functionality and visual elements to create a system that is not only operational but also usable and adaptable to changing user needs.

The UI also needs to be reliable and work as expected to satisfy the user. This adds to the trustworthiness of the experience and helps users (especially those with short attention spans) stay engaged with the site and app. 

Another crucial aspect is the usability and ease-of-use of the interface. According to the Interaction Design Foundation, a usable interface has three main outcomes:

  1. It should be easy for the user to become familiar with and effectively navigate the user interface during the first contact, 
  2. It should be easy for the user to achieve their objective, and 
  3. It should be easy to recall how to interact with the user interface on subsequent visits.

Finally, UIs should provide users with a delightful experience, which means they should have a positive emotional reaction when interacting with a device or interface. According to UI and UX consulting firm Nielsen Norman Group, delight may not always be expressed outwardly but can influence a user’s behaviors and opinions while they’re using a website or application. Surface delight can be achieved with animations, sound interactions, or an interjection of humor into the copy, but true, deep delight only occurs when the above criteria (functional, reliable, and usable) are fulfilled and the user is fully immersed in the experience without any distractions. It’s achieved by building a product that works as expected (or better) and meets user needs at the right time and place. 

Types of UI and basic design requirements for each type

Most UIs these days are graphical user interfaces (GUIs), which include text, links, buttons, and images. They were originally introduced in reaction to the perceived steep learning curve of command-line interfaces (CLIs), which require commands to be typed on a keyboard. 

UI design was revolutionized in 2007 with the introduction of the iPhone, which brought touch to user interfaces. While a GUI relies on the sense of sight, a touch-based UI relies on the sense of touch to complete tasks, which adds another level of interaction (especially for users with visual impairments). 

One step further is gesture interfaces, which enable users to control the computer via body motion and gestures without touching a keyboard, mouse, or screen.

Conversational user interfaces (CUI) mimic a conversation with a real human and can take the form of chatbots or voice assistants such as Alexa or Siri. Increasingly, these interfaces are screenless (or headless), and this can change the way we seek information or carry out tasks. As the UI is simpler and more intuitive, users can interact with it in the background while working, driving, or socializing. 

Next steps

So, a user interface is the access point of a machine, product, or device a person interacts with. For UIs to be truly user-friendly (whether they have a screen or not), they must be functional, reliable, usable and delightful. They are an essential element of user experience. If you get the UI right, onboard users and keep them engaged, you are well on your way to create a successful product. Remember, the best UI is one that users don’t even realize they’re using.