What is a user interface?

A user interface (UI) refers to the visible and in­ter­act­ive part of a software or hardware system. It typically includes elements such as buttons, menus, and icons. However, there are also al­tern­at­ive in­ter­faces that can be con­trolled through text, voice, or even brain activity.

What is a UI (user interface)?

A user interface (UI) is the point of in­ter­ac­tion between humans and machines. It enables you to operate a computer, place an order in an online shop, or use an app on your smart­phone. The user interface includes all visible and in­ter­act­ive elements, ranging from simple text-based command lines to complex graphical user in­ter­faces.

The design of a user interface has a major impact on how easy and com­fort­able software or a website is to use. Today, the focus is not only on func­tion­al­ity, but also on visual appeal and usability. User ex­per­i­ence has therefore become a central aspect of UI design. The goal is to create intuitive in­ter­faces that support a smooth and efficient user journey. While graphical user in­ter­faces are still the most common approach, new and in­nov­at­ive UI types are in­creas­ingly shaping how people interact with digital systems.

What types of UIs are there?

Since the invention of computers, methods of human–machine in­ter­ac­tion have steadily evolved. Today, a wide range of user interface types exists. Early systems relied on simple command-line in­ter­faces (CLI), while later in­nov­a­tions such as natural user in­ter­faces (NUI) have made in­ter­ac­tion more intuitive and direct. The following table provides an overview of the most important UI types before they are explained in more detail.

Command Line In­ter­faces (CLI)

In the early days, user in­ter­faces were just as minimal as the first computer systems them­selves. Screens typically showed nothing more than a command line and a prompt in­dic­at­ing the current position or awaiting input, as seen on early MS-DOS machines. Users in­ter­ac­ted with the system by entering commands via a command-line interface. The computer would then process the input and return the result in text form.

Although this type of interface is now con­sidered outdated, it is still used in tools such as cmd.exe on Windows systems, where the syntax largely follows its DOS origins. In­ter­ac­tion in a CLI is handled entirely through the keyboard, without the use of a mouse.

In summary:

✓ CLI is the first method for operating the user interface.

✓ With a text-based user interface, in­ter­ac­tion is con­trolled via keyboard input.

✓ Inputs are entered and executed in a command line (line-oriented).

Text User Interface (TUI)

Text user in­ter­faces are more user-friendly than command-line in­ter­faces, although in­ter­ac­tion still takes place entirely via the keyboard. They represent a trans­ition­al stage between pure command-line in­ter­faces and graphical user in­ter­faces. The term ‘TUI’ was in­tro­duced after GUIs became wide­spread to clearly dis­tin­guish text-based in­ter­faces from both CLIs and graphical systems.

Unlike CLIs, TUIs use the entire screen rather than a single line, allowing for more struc­tured layouts. However, they still operate in text mode. Typically, a fixed set of char­ac­ters is available, which can be arranged to create menus, windows, or simple interface elements. TUIs are still used today, for example in boot­load­ers or BIOS setup programs.

In summary:

✓ TUIs are text-based user in­ter­faces that use the full screen and support more complex layouts than CLIs.

Graphical User In­ter­faces (GUI)

GUIs (Graphical User In­ter­faces), i.e., graphical user in­ter­faces, are the es­tab­lished standard today. Software is now operated using graphical controls and icons, which are often visually modelled on objects from the ‘real world’. Users typically interact using a mouse and keyboard, but touch­screens are now just as common. Graphical user in­ter­faces in­tro­duced familiar elements such as the desktop, windows, and the recycle bin into the digital en­vir­on­ment. Users can select and open these elements with simple actions like clicking or tapping.

The graphical design is typically based on the tra­di­tion­al office en­vir­on­ment, making elements easy to recognise and use. As a result, in­ter­ac­tion is more intuitive than working with the command list of a command-line interface. Even beginners can quickly un­der­stand what icons represent, as familiar symbols like a rubbish bin or an envelope require little ex­plan­a­tion. This kind of visual language has become just as standard as GUIs them­selves, and most graphics programs use tool icons that reference real-world objects.

In summary:

✓ GUIs are the standard today.

✓ GUI describes a graphical user interface in which operation works by clicking or tapping graphical icons.

Voice User Interface (VUI)

Although graphical user in­ter­faces are now wide­spread, UI de­vel­op­ment has not stopped there. Voice user in­ter­faces make it possible to interact with machines through voice commands. Most modern operating systems include this type of interface, such as Apple’s Siri or voice input in Google Search. Users can open ap­plic­a­tions by speaking and have spoken text auto­mat­ic­ally tran­scribed, which can improve ef­fi­ciency. Voice control also enhances ac­cess­ib­il­ity, making tech­no­logy easier to use for a wider range of people.

In summary:

✓ VUIs offer a voice-con­trolled user interface that enables in­ter­ac­tions via spoken commands.

✓ VUIs support ac­cess­ib­il­ity.

Natural User Interface (NUI)

In­ter­ac­tion with machines becomes es­pe­cially intuitive with a natural user interface. An NUI builds on graphical and voice-based in­ter­faces by enabling more direct and natural forms of com­mu­nic­a­tion. It responds to gestures, movement, and speech, and can also in­cor­por­ate facial and object re­cog­ni­tion. Sensors, cameras, and mi­cro­phones allow users to interact with systems in a variety of ways.

Many modern smart­phones and tablets in­creas­ingly rely on NUI tech­no­lo­gies, and devices like Nintendo’s Wii console have pop­ular­ised gesture and motion control in an intuitive way. Smart­watches, as well as ap­plic­a­tions and devices based on Augmented Reality (AR) and Virtual Reality (VR), also make extensive use of natural user in­ter­faces. Core features include gesture control, speech re­cog­ni­tion, and facial re­cog­ni­tion, all of which con­trib­ute to a more intuitive way of in­ter­act­ing with tech­no­logy. In addition, NUIs are in­creas­ingly enhanced with AI to interpret spoken and physical inputs more ac­cur­ately and to better connect digital systems with the physical world, creating a more dynamic user ex­per­i­ence.

In summary:

✓ NUIs enable easy operation based on gestures, movements, speech, and object re­cog­ni­tion.

✓ NUIs are often enhanced and optimised with AI tech­no­lo­gies.

Gen­er­at­ive User In­ter­faces (GenUI)

A gen­er­at­ive user interface (often also called GenUI) refers to a new type of user interface in which ar­ti­fi­cial in­tel­li­gence dy­nam­ic­ally generates or adapts parts of the interface in real time. This means that layouts, com­pon­ents, or functions auto­mat­ic­ally change depending on what the user is currently doing or needs. Unlike classic static UIs, which look the same for many users, a gen­er­at­ive UI can be per­son­al­ised, context-sensitive, and situ­ation­ally adapted so that, for example, relevant in­form­a­tion, buttons, or views are displayed exactly when they are needed.

In summary:

✓ GenUIs are dy­nam­ic­ally generated user in­ter­faces that work with ar­ti­fi­cial in­tel­li­gence.

✓ They learn from data and in­ter­ac­tions to make the user interface context-sensitive, in­di­vidu­al­ised, and adaptive.

✓ Gen­er­at­ive UIs shift the focus from fixed design to tailored ex­per­i­ences.

What special types of UIs are there?

In addition to these types of user in­ter­faces that are common in everyday life, there are some ‘exotic’ forms and in­nov­a­tions that have not yet reached the mass market. These include the Tangible User Interface, also ab­bre­vi­ated as TUI, the Per­cep­tu­al User Interface (PUI), and the Brain Computer Interface (BCI). The following table provides an overview of these user in­ter­faces before they are presented in­di­vidu­ally.

Tangible User Interface

Tangible User In­ter­faces (also ab­bre­vi­ated as TUI, not to be confused with Text User Interface) are physical, touchable user in­ter­faces. This means in­ter­ac­tion with the machine takes place via physical objects. Cubes, spheres, or other objects are ma­nip­u­lated by the user (rotated, pressed, etc.), trig­ger­ing mech­an­isms or re­triev­ing digital in­form­a­tion. Tangible User In­ter­faces are often used in museums or at trade shows.

Per­cep­tu­al User In­ter­faces

The de­vel­op­ment of Per­cep­tu­al User In­ter­faces (PUI) is still in its infancy, but is in­creas­ingly being driven forward by the sci­entif­ic community. This type of user interface is per­cep­tion-driven, meaning it combines VUI, GUI, and elec­tron­ic gesture re­cog­ni­tion.

Brain Computer In­ter­faces

Brain Computer In­ter­faces (BCIs) are no longer science fiction. Using elec­trodes, brain activity can be measured and trans­lated into control commands by al­gorithms. Re­search­ers have already achieved early successes, such as enabling a paralysed patient in the United States to control a robotic arm using her thoughts. In the future, BCIs could transform ac­cess­ible in­ter­ac­tion with computers and other machines.

How can you optimise your user interface?

Anyone involved in web design should pay close attention to user in­ter­faces. If you want to engage users of your app, attract visitors to your website, or succeed with your online shop, the ex­per­i­ence needs to be as intuitive and straight­for­ward as possible. A key first step is un­der­stand­ing your target audience so you can tailor both the user interface and the overall user ex­per­i­ence ac­cord­ingly. The func­tion­al­ity, ease of use, and visual appeal of your product are all essential factors in de­liv­er­ing a strong user ex­per­i­ence.

Step 1: Optimise usability

To improve your UX, start by focusing on the graphical user interface. Usability should always be a priority, including how ef­fi­ciently and ef­fect­ively users can interact with your product and how satisfied they feel while doing so. If an app or website is difficult to navigate, even a visually appealing design will not be enough to win users over.

Op­tim­ising your website or app typically requires thorough testing. User studies, along with technical methods such as heatmap analysis, can provide valuable insights. These tools visualise user behaviour by tracking clicks, scrolling, mouse movements, or even eye-tracking, and display the results using colour gradients.

Step 2: Visual fine-tuning

Once func­tion­al­ity and ease of use are ensured, you can move on to the aes­thet­ics of your project. Here, less is usually more. The design should support the func­tion­al­ity of the graphical user interface and therefore be clear and well-struc­tured. That doesn’t mean designers can’t get creative. It simply means you need to un­der­stand your target audience’s usage habits and avoid re­strict­ing func­tion­al­ity through design.

Why are intuitive user in­ter­faces so important in web design and software de­vel­op­ment?

Why does an intuitive user interface matter so much? A simple example high­lights this. A butterfly icon may look at­tract­ive, but most users would not associate it with the ‘Save’ function. By contrast, the floppy disk icon has long been linked to saving, even though the tech­no­logy itself is outdated. Users expect familiar symbols and rely on them in­stinct­ively. For this reason, it’s important to follow es­tab­lished icon con­ven­tions and only deviate from them with careful con­sid­er­a­tion.

This example shows that web design always involves balancing aes­thet­ics and func­tion­al­ity. A visually at­tract­ive design alone is not enough if it com­prom­ises usability. Op­tim­ising the user interface is essential to deliver the best possible user ex­per­i­ence. Depending on the purpose of the website or ap­plic­a­tion, this can lead to higher con­ver­sion rates or increased user re­com­mend­a­tions.

What role does the graphical user interface play in SEO?

A good graphical user interface has a positive impact on your ranking. If users can find their way around your website, they feel com­fort­able and spend more time there—an important factor, since search engines now use time on site to determine how relevant a page was for a par­tic­u­lar search query. When designing your website’s GUI, you should always put yourself in the shoes of visitors who are accessing your site for the first time. If they can’t find their way around on their first visit, they’ll quickly leave the page and look for easier-to-use al­tern­at­ives. So, the key concept here, just as in software de­vel­op­ment, is intuitive nav­ig­a­tion.

A good nav­ig­a­tion structure can be achieved, for example, through mean­ing­ful internal links that visitors can use to click through your website. The search engines’ web crawlers also follow these links. Any path should always be clear and not too long. A useful measure is the bread­crumb nav­ig­a­tion. It makes the user interface much more user-friendly, since visitors can always clearly see where they are on the site and where they can navigate back to if needed.

Best practices for user interface design in web design

Since there are many types of user in­ter­faces, it would go beyond the scope here to list best practices for each category. However, the following examples from web design il­lus­trate fun­da­ment­al guidelines for an intuitive user interface and show what im­ple­ment­a­tion can look like in practice.

Evernote

Evernote is a note-taking ap­plic­a­tion that allows users to sync their content across devices, making ideas ac­cess­ible at any time. Its homepage uses a clean and well-struc­tured graphical user interface that clearly high­lights features, use cases, and benefits, making it easy for users to get started.

The re­gis­tra­tion form is kept simple. It only asks for an email address, and then you set your password. Al­tern­at­ively, Evernote offers re­gis­tra­tion via a Google or Apple account, which sig­ni­fic­antly reduces the re­gis­tra­tion effort for users.

Evernote is available as a native app on nearly every platform. Its web interface is fully re­spons­ive, adapting seam­lessly to different screen sizes. This design approach improves the overall user ex­per­i­ence, allowing users to access and use the app anytime, anywhere, and on any device.

Google

Almost everyone knows Google, and one of the many reasons is that the user interface is as simple as it is func­tion­al and visually appealing. A search bar and two buttons on a tra­di­tion­ally white back­ground are enough for one of the most re­volu­tion­ary tech­no­lo­gies in computer history. You won’t find un­ne­ces­sary design gimmicks or nested menus. With Google Doodles, however, the company still shows a sense of humour and loosens up the design on special occasions—of course without affecting usability.

The app icons for YouTube, News, Maps, and other services are easy to locate and can be opened with a single click. Their design is clear, intuitive, and visually reflects the function of each app. The in­teg­ra­tion of a voice user interface is also note­worthy, as Google supports voice search directly within its mobile app. With Voice Match enabled, the Assistant re­cog­nises your voice and provides per­son­al­ised results.