UI Components: Building Blocks of User Interfaces

UI components are the essential building blocks of any user interface, functioning like the individual pieces of a digital construction set. From basic elements such as buttons and text inputs to more intricate structures like carousels and modal windows, these self-contained and reusable units enable the efficient creation of interactive and visually cohesive applications.

By strategically combining and customizing these pre-built modules, developers and designers can construct sophisticated user experiences while ensuring consistency and simplifying maintenance. A thorough grasp of the wide spectrum of UI components and their appropriate utilization is crucial for crafting user-friendly and impactful digital products.

What Are UI Components?

User interface (UI) components – also known as UI elements or controls – are distinct, reusable building blocks of software interfaces (What are Components in Digital Design?). They are the parts used to construct apps or websites, providing the visual elements and interactive touchpoints that users see and engage with.

For example, buttons, scrollbars, menu items, checkboxes, and other on-screen elements are all UI components (32 UI Elements Designers Need To Know: 2025 Guide). Each component typically serves a specific function or interaction need (e.g. a button triggers an action), and together these pieces combine to create the overall user experience (atlassian.design).

In essence, a UI component is a self-contained piece of the interface that can be developed and thought about in isolation. Modern development frameworks like React emphasize this by letting you “split the UI into independent, reusable pieces, and think about each piece in isolation.” (Components and Props – React)

This modular approach means that instead of building an entire UI screen as one large monolithic page, you break it down into components (for example, a navigation bar component, a form component, a footer component). Each component can be designed, coded, and tested on its own, then assembled like LEGO blocks to form complex interfaces.

Here’s the list of common and fundamental UI components with names:

Input Controls:

• Text Field / Input Box: Allows users to enter and edit text. Can be single-line or multi-line.
• Checkbox: Enables users to select or deselect one or more options from a set.
• Radio Button: Allows users to select only one option from a predefined set.
• Dropdown / Select: Presents a list of options from which the user can choose a single value. Often conserves screen space.
• Slider: Enables users to select a value within a continuous range by moving a thumb along a track.
• Toggle Switch: Represents an on/off state or a choice between two distinct options.
• Button: Triggers an action or navigates the user to another part of the interface when clicked or tapped. Can have various styles and states.
• File Upload: Allows users to select and upload files from their local storage.

Navigation:

• Navigation Bar: A set of links or buttons that help users move between different sections or pages of an application or website.
• Tabs: Organizes content into multiple panes, allowing users to switch between them by clicking on labels or icons.
• Breadcrumbs: A hierarchical trail of links indicating the user’s current location within a website or application. Aids navigation and understanding of site structure.
• Pagination: Divides large sets of content into discrete pages, allowing users to navigate through them sequentially.
• Sidebar: A vertical panel, often on the left or right, used for primary or secondary navigation, or to display supplementary information.
• Menu: A list of options or commands presented to the user, often triggered by a button or icon (e.g., hamburger menu).

Information Display:

• Text / Typography: Displays written content, including headings, paragraphs, labels, and captions. Crucial for readability and conveying information.
• Icon: A visual symbol used to represent an action, state, or concept, often used in conjunction with text or as a standalone interactive element.
• Image: Displays static visual content.
• Video: Displays moving visual content.
• List: Presents a series of items in a vertical or horizontal arrangement. Can be ordered or unordered.
• Table: Displays data in a structured format with rows and columns, facilitating comparison and analysis.
• Tooltip: A small informational pop-up that appears when a user hovers over an element, providing context or hints.
• Progress Bar: Visually indicates the progression of a task or process.
• Notification / Alert: Conveys important information, warnings, or errors to the user, often requiring acknowledgment.
• Badge / Label: A small visual indicator used to highlight or categorize items, often displaying a count or status.

Containers:

• Card: A rectangular container that groups related information or actions. Often used to display concise summaries or previews.
• Accordion: A vertically stacked list of items, where each item can be expanded or collapsed to reveal or hide content.
• Modal / Dialog: A temporary window that appears on top of the main application content, requiring user interaction before the main content can be accessed again.
• Carousel / Slider: Displays a series of content items (images, text, etc.) that can be navigated through horizontally or vertically.

Feedback & Hints:

• Toast / Snackbar: A brief, non-intrusive message that appears temporarily to provide feedback on an action.
• Tooltip: (Also listed under Information Display, as it provides information upon interaction).
• Placeholder Text: Hint text displayed within an input field that disappears when the user starts typing.

Why Use UI Components (Modularity and Reusability)

UI components are fundamental to building modular, reusable, and maintainable interfaces. Because they are self-contained and reusable, components allow developers and designers to build once and reuse the same element across many parts of an application.

This significantly reduces code duplication and enhances maintainability, since a change to a component (like fixing a bug or updating the style of a button) will automatically propagate to every interface that uses it (Writing Reusable UI Components: Best Practices and Naming Conventions | by Suraj Kurade | nonstopio).

Reusable components also simplify development by providing a consistent structure – teams can collaborate more easily when the UI is composed of well-defined pieces, and a library of components ensures a consistent look and behavior throughout the product.

Using components promotes consistency in design. Many organizations create design systems or UI libraries which define a set of standard components (with predefined styling and behavior) to be used across all their products.

This consistency helps users learn the interface faster (since a button or slider looks and works the same everywhere) and improves the overall user experience. Components are often documented with guidelines so that designers and developers can implement them uniformly. For example, Atlassian’s design system states that components are “reusable building blocks” that meet specific interaction needs and combine to create intuitive user experiences. (atlassian.design) By reusing the same building blocks, the interface remains coherent and scalable as it grows.

(What are Components in Digital Design?) Example of a collection of UI components prepared in a design tool. Each module (buttons, inputs, menus, etc.) is defined once and can be reused throughout the application’s design (What are Components in Digital Design?). Defining components in a central library like this ensures consistency and speeds up development when building new screens.

(What are Components in Digital Design?) Screens from a mobile app, each composed of standard UI components (headers, text sections, buttons, etc.). The same set of components is reused across different screens, which creates a consistent look and feel (What are Components in Digital Design?). This reuse also makes it easier to modify the UI – adjusting a component in the library updates it everywhere it appears.

In software engineering terms, UI components encourage the DRY principle (“Don’t Repeat Yourself”). Rather than writing new code for every button or form, developers create a component once and reuse it. This leads to more maintainable code and a more systematic development process. “Reusable components simplify the development process, reduce code duplication, and enhance code maintainability. They allow you to create a consistent and modular UI, which is vital for building scalable applications.” (Writing Reusable UI Components: Best Practices and Naming Conventions | by Suraj Kurade | nonstopio) In summary, by using UI components, teams can build complex interfaces more efficiently, ensure consistency across the application, and more easily maintain and update the UI over time.

Common Types of UI Components

There are many types of UI components, ranging from simple to complex. Most UI elements fall into a few broad categories based on their purpose (32 UI Elements Designers Need To Know: 2025 Guide):

Input Controls

These allow users to input or select information. Examples include buttons, sliders, text fields, checkboxes, radio buttons, toggle switches, and dropdown lists. For instance, a button is typically a clickable element (often a rectangular shape with a label) that triggers an action or submits data when pressed (32 UI Elements Designers Need To Know: 2025 Guide). A slider (or range slider) lets users select a value or range by dragging a handle along a track – this is common for adjusting settings like volume or brightness. Input fields are boxes where users can type text (such as a search box or a form field to enter an email). Each of these controls accepts user input in a specific format (a button click, a chosen value, typed text, etc.).

Navigational Components

These help users move around within an app or website. Examples include menus (e.g. a hamburger menu on mobile, which hides/show navigation links), tab bars or navigation bars (common in mobile apps for switching views), breadcrumb trails (links that show the page hierarchy and allow navigation back to previous pages) (32 UI Elements Designers Need To Know: 2025 Guide), and pagination controls (to navigate between pages of content). These components organize the interface and provide pathways for the user to explore different sections.

Informational Components

These are used to display information to the user or to inform them of something. Examples include labels (text that simply informs or describes other elements), tooltips (small pop-up text that appears when you hover over an element, providing context or guidance), notifications (messages or badges indicating new events or errors), and modal dialogs (overlays that present important information or ask the user to make a decision). For example, a modal dialog might appear to confirm a user’s action (like confirming deletion of an item) and typically contains text and buttons for the user’s response.

Containers and Structure

These components hold other content or groups of components together. They define layout or organizational structure on the interface. Examples include forms, cards, accordions, panels, and other groupings.

A form is essentially a container that includes input fields, checkboxes or radio buttons, and a submit button, allowing users to input a set of related information and send it (such as a registration form with multiple fields) (32 UI Elements Designers Need To Know: 2025 Guide).

An accordion is a container that can expand or collapse to show/hide content sections, helping to organize large amounts of information in a limited space (for instance, an FAQ list with expandable answers (32 UI Elements Designers Need To Know: 2025 Guide)).

Card components are another common container – usually a rectangular box that groups text, images, and buttons about a single subject (like a product card with product image, name, price, and an “Add to Cart” button). Containers help in structuring the interface into logical sections.

Each type of UI component has a well-understood role. Designers and developers choose components based on what the user needs to do. For example, if a user must choose one option from many, a set of radio button components or a dropdown component might be used; if they need to toggle a setting on/off, a switch component is suitable; to navigate to a different page, a link or button might be used; to display status, an alert or progress bar component could appear.

By mixing and matching these components, nearly any user interface can be constructed. Importantly, these components behave consistently across applications – a button on a mobile app and a button on a website may look slightly different per platform style, but both serve the same purpose of initiating an action.

UI Components Across Web, Mobile, and Desktop

One of the powerful aspects of UI components is that the concept applies across different platforms and frameworks. Whether you are building a web app, a mobile app, or a desktop application, you will use UI components – though the specific implementation and naming might differ:

Web (Browsers)

On the web, HTML itself provides basic UI components (often called HTML elements) such as <button>, <input> (text fields, checkboxes, radio), <select> (dropdown menus), and more. These are the foundational components of webpages.

Web developers also use JavaScript frameworks/libraries like React, Angular, or Vue, which allow defining custom components. In React, for example, everything on the screen can be built from components written in JSX/JavaScript.

React components are essentially JavaScript functions or classes that output UI elements; they “let you split the UI into independent, reusable pieces” so you can build complex UIs from small parts (Components and Props – React).

Web components (a standard Web Platform feature) also allow developers to create reusable custom HTML elements that work natively in browsers. Overall, in web development you might have a component for a navigation bar, a component for a user profile card, etc., which you can include on any page as needed.

Mobile (iOS and Android)

Mobile platforms have their own sets of UI components, often provided by the platform’s SDK. In iOS (Apple) development, if using the older UIKit framework, you have classes like UIButton (button), UILabel (text label), UISlider (slider control), etc., which can be laid out in Interface Builder (storyboards) or created in code.

Newer iOS apps often use SwiftUI, which is a declarative UI framework. In SwiftUI, views are the basic components – for example, Text, Image, Button are all views, and you compose them to build the interface. “Views are the fundamental building blocks in SwiftUI. They represent your app’s UI and can be composed of other views.” (Basic Components in SwiftUI. SwiftUI is a powerful framework for… | by minal kewat | Medium).

So a SwiftUI button is created by combining a Button view with a label (like a Text view inside it) and an action. These mobile components follow platform design guidelines (e.g., an iOS button will by default follow Apple’s Human Interface Guidelines for appearance and behavior).

On Android, the traditional way to build UIs is by using XML layout files to declare UI components (called Views in Android). The Android SDK provides a library of UI widgets like Button, TextView (label), EditText (text input field), ImageView (image display), SeekBar (slider), etc. The XML layout describes how these components are arranged on the screen, and the app’s code (in Java/Kotlin) can interact with them.

For example, an Android layout XML might define a Button with certain text and size, and in code you assign it a click listener. “XML lays down the structure and defines the properties of UI elements like TextViews, ImageViews, Buttons, and many more”, separating the layout design from the app logic (Jetpack Compose vs XML for Android UI Development).

Modern Android development also offers Jetpack Compose, which is a newer declarative UI toolkit (conceptually similar to SwiftUI). In Jetpack Compose, you build UI components with Kotlin functions – for instance, there is a Button composable, a Text composable, etc., and you compose them together in code to create the interface. Regardless of approach, Android developers are still using a set of standard UI components under the hood.

Desktop

Desktop applications (Windows, macOS, Linux, etc.) also use UI components. Many desktop UI frameworks provide a palette of controls like buttons, text boxes, menus, checkboxes, tables, and so on.

For example, Windows developers using .NET might use WinForms or WPF controls (like a Button control, a TextBox control, etc.), and macOS developers using AppKit have NSButton, NSTextField, etc. Cross-platform frameworks (like Qt or JavaFX) likewise offer UI widgets that mirror these common components.

The idea is the same: a desktop app window is built by arranging components in layouts. A form in a desktop app might use text fields and combo boxes; a navigation might use a tree view or menu components.

The consistency of using standard components ensures that desktop apps adhere to familiar UI behaviors (for instance, a user expects a checkbox on Windows to look and toggle a certain way, which the standard component provides).

Despite differences in platform technology, the concepts are parallel. A “button” exists in web, iOS, Android, and desktop, though implemented with different code, it serves the same purpose. UI component libraries/frameworks on each platform provide these building blocks so that developers do not have to reinvent basic elements from scratch for each app.

Moreover, design principles carry over: for example, the need for clear affordances (a button should look clickable) and feedback (showing a slider’s current value) is universal, so UI components are designed with these in mind across platforms.

Conclusion

UI components are the foundation of user interface design and development. They encapsulate visual appearance and behavior into modular pieces that can be reused and combined to build complex interfaces.

By using UI components, designers and developers achieve a more structured and efficient workflow: the interface becomes a puzzle that can be assembled from known pieces, rather than a giant bespoke creation.

This leads to interfaces that are consistent, easier to navigate for users, and easier to maintain and upgrade for teams. As you learn UI design and development, understanding common components (like buttons, sliders, forms, menus, etc.) and how to implement them in your chosen platform is key.

Mastering UI components – and the patterns of using them – will allow you to create intuitive, user-friendly designs and scalable applications with far less effort than coding every screen from scratch. In short, thinking in terms of components is now a best practice in building modern user interfaces, enabling both great design and robust engineering. (Writing Reusable UI Components: Best Practices and Naming Conventions | by Suraj Kurade | nonstopio)