Web Components with Lit: Practical Guide for Reusable UI

Lit (formerly lit-element) simplifies the creation of modern Web Components by offering a declarative model, lightweight reactivity, and full support for the Custom Elements pattern. In 2025, Lit is the preferred choice for UI libraries that need to be framework-agnostic.

Why choose Lit?

Native compatibility, works in all modern browsers without external dependencies.
Performance, minimal rendering thanks to lit-html and property-based updating.
Shadow DOM, encapsulation of styles and markup, ensuring isolation.
Simple reactivity, just declare properties and Lit takes care of the update.

Basic structure of a Lit component

A Lit component extends the base class LitElement and brings together three elements: encapsulated styles, declared statically to be reused in each render; reactive properties, which trigger automatic updates when they change; and a declarative, template-based rendering method. Interaction with the external world happens through customized events, a button, for example, emits its own event when clicked, instead of coupling business logic to the component. Finally, the element is registered as a native Custom Element, making it available to any page or framework as a common HTML tag.

Good performance practices

Use static get styles, avoid recreating CSS with each render.
Only update observed properties, Lit detects changes and updates the DOM efficiently.
Avoid innerHTML, prefer Lit template html to prevent XSS.
Lazy-load components, load components on demand with import().

Accessibility (a11y)

Set relevant ARIA attributes (role, aria-label).
Ensure visible focus using :focus-visible.
Test with screen readers (NVDA, VoiceOver).

The component's rendering template should include attributes like aria-label linked to the properties themselves, ensuring that the label read by screen readers follows the button's visible content without additional work.

Integration with Design Systems

Lit can serve as the base layer for a design system. The recommendation is to centralize the design tokens, colors, typography, spacing, in a separate module and import them into the components. Thus, each button or card consumes the palette from a single source of truth, and a brand change propagates throughout the system by changing only the token module.

Automated tests

Use @web/test-runner or Playwright to validate behavior and visual regressions. Both install as development dependencies and run against the project's test files, covering everything from component rendering to user interactions and pixel comparisons.

Deploy and distribution

npm package, publish as @yourorg/ui-components.
CDN, make it available via jsDelivr or unpkg for direct use in HTML.
Storybook, document and visually test each component.

Implementation checklist

Define design tokens (colors, typography, spacing).
Create base components (Button, Input, Card) using Lit.
Configure lint (ESLint) and format (Prettier).
Write unit and integration tests.
Document with Storybook and generate publication artifacts.
Publish to npm and/or CDN.

Conclusion

Lit offers a lightweight, standardized path to creating reusable Web Components, with a focus on performance, accessibility and interoperability. By adopting the best practices described, you build UI that can be consumed by any application, regardless of the framework.

Which Lit component would you like to see in the next post? Share in the comments!