Web Components: Build UI Kits for all UI Frameworks

Web Components Structure

Web Components are built upon 3️⃣ core technologies:

• Custom Elements
• Shadow DOM
• and HTML Template
• Plus, a versatile feature called Slots.

Earlier, there was also another core feature ‒ HTML Imports used to load one HTML document into another HTML document. But now it’s deprecated everywhere.

Below, on the right of the screen, you can see an example of a simple Web Component utilizing all these core features at once:

Now, let’s break down what makes each of these so game-changing!

Shadow DOM — True HTML & Style Isolation

Remember when some global CSS from a library in the node_modules ruined your UI elements’ styling in the project?

The Shadow DOM puts an end to that chaos! It gives every component its own private Shadow DOM tree.

Styles and layout inside are encapsulated — totally protected from the outside world:

This means:

• NO more CSS conflicts!
• NO more unexpected side effects!
• NO more bleeding styles!

At the very heart ♥️ of Web Components, we have exceptionally elegant Custom Elements.

They allow you to create your own HTML tags — with behavior, styling, and business logic baked in.

With Custom Elements, you gain the power and flexibility to your elements through:

• Lifecycle hooks:
  • connectedCallback — when the element is mounted to the DOM;
  • disconnectedCallback — when the element is UNmounted from the DOM.
  • attributeCallbackChanges — when the element attributes get updated in the DOM
  • and others!
• Custom properties and attributes
• Inheritance & Composition
• Customized Styling
• Custom Events
• Data bindings
• and a lot more!

In short:

You get full control over your frontend component’s architecture, behavior, and look-and-feel, with ZERO external library needed!

It’s like building your own React components — but entirely browser-native 😅 Plus, you’ll be able to use them in ANY other framework and library like Angular, Svelte, Vue, Stencil, Qwik, and others!

HTML Templates — Reusable DOM Trees on Steroids

HTML Templates are your tool for defining markup once and reusing it anywhere.

Think of them like blueprint components — hidden and inert by default, but ready to clone and inject dynamically.

Paired with Shadow DOM and Custom Elements, these HTML Templates allow you to build truly dynamic UIs that are:

• Lightweight
• Reusable
• Declarative
• Composable
• Fully native

They also play nicely with advanced tools like Document Fragments and custom styling strategies.

🎭 Slots — Content Projection, Supercharged

Need to let other developers insert content into your component from outside?

Enter Slots — the built-in solution for Content Projection.

Slots make your component APIs much more flexible, powerful, and elegant.

They come with a bunch of features like named slots, nested slots, multi-level slots, change tracking, and more!

This Content Projection mechanism operates on the principle of Separation of Concerns, allowing developers to decouple one component’s logic and content from the other.

UI Frameworks with Web Components

But hey! DID YOU KNOW THAT? Many popular Frontend Frameworks, such as Angular, Svelte, Vue, Lit, and others, have already integrated the Web Components API into their ecosystems!

For instance,

• 🍏 Vue
  • Provides a shadowRoot: true property that allows for manipulating the Shadow DOM and encapsulating styles:
  • Vue provides an official @vue/web-component-wrapper for exporting components as Custom Elements
  • Supports props/attributes, slots, and event emission in native Web Component format
• 🍊 Svelte
  • Offers a customElement: true compiler option to build native Custom Elements
  • Supports Shadow DOM and Slots natively when compiling to Web Components
  • Integrates Form-Associated Elements with Element Internals API
• 🍒 Angular
  • Employs the Shadow DOM for encapsulation
  • Supports consuming Custom Elements out of the box
  • Easily integrates Web Components into Angular templates

Of course, this list isn’t complete. Many other modern frameworks and libraries, and even older ones — can consume Web Components. The beauty behind them is that they aren’t tied to any framework, making them the perfect glue for building interoperable, future-proof UI across diverse tech stacks.

When You’ll Want to Use Web Components

Web Components shine in scenarios where traditional UI frameworks hit their limits. You might need them when:

• You’re a Frontend Engineer (Angular, React, Svelte, Vue, etc.) looking to build framework-agnostic components that work everywhere — even outside your current stack.
• You’re developing or maintaining a Design System, UI Kit, or Component Library and want to ship it once, then reuse it across multiple projects or teams.
• You’re an Architect implementing Micro-Frontend architectures or monorepos, and you need solid UI isolation and cross-team compatibility.
• You’re a Full-stack / Backend Developer working with:
  • SSR frameworks like Next.js, Nuxt.js, or Angular Universal
  • Template-based stacks like JSP, Razor/ASP.NET, or PHP — where you still want a dynamic, reusable UI without full framework coupling
• You’re bridging between the old and new tech stack. For instance, you’re integrating the features from a legacy UI framework (like Backbone, AngularJS, Knockout) into your modern projects, OR vice versa.

Final Thoughts

As you see, Web Components aren’t just another tool in the frontend toolbox — they’re a native, stable, and scalable foundation for building modern web applications. They solve real problems developers face every day: framework lock-in, brittle styling, inconsistent APIs, and integration nightmares. And yet, despite being supported by all modern browsers — they remain one of the most powerful yet underused technologies in web development.

If you have questions about the Web Components API or anything related to Software Development – I’m always happy to help! 💚

Feel free to leave me a comment in the Q&A section below or on my Telegram.

Let’s build the IT future we could be proud of together! 🚀 I hope you’ll love the Web Components as much as I did!