Understanding Web Components

August 23, 2025

Web Components are a suite of technologies that let you create encapsulated, reusable custom elements for the web. Think of them as building blocks that anyone can drop into a page without worrying about naming collisions, style leakage, or unexpected behavior.

Three pillars at a glance

Custom Elements – Define your own HTML tags (e.g., <x-card>) and register them with the browser.
Shadow DOM – Encapsulate DOM & CSS so a component’s internals don’t bleed out.
HTML Templates – Reusable chunks of markup that stay inert until instantiated.

Why bother?

**Encapsulation** – No more global CSS headaches.
**Interoperability** – Use components in React, Vue, or plain JavaScript.
**Future‑proof** – Native browser support means no more polyfills in the long run.

A quick example


// Define the class
class HelloCard extends HTMLElement {
  constructor() {
    super();
    // Attach a shadow root
    const shadow = this.attachShadow({mode: 'open'});
    const wrapper = document.createElement('div');
    wrapper.innerHTML = `Hello, ${this.getAttribute('name')}!`;
    shadow.appendChild(wrapper);
  }
}
// Register the element
customElements.define('hello-card', HelloCard);

Now you can use it anywhere:

<hello-card name="Soham"></hello-card>

Web components animation — Illustration of component encapsulation

That’s the gist – with this foundation you can build anything from a simple toggle to a full‑blown data grid.