Browser Support
ARC UI targets modern evergreen browsers. All components use native Web Components APIs (Custom Elements v1 and Shadow DOM v1).
Overview
ARC UI is built on Lit 3 and ships as ESM-only
(type: "module"). No ES5 or legacy module builds are provided.
Supported Browsers
Web Components APIs
| API | Chrome | Firefox | Safari | Notes |
|---|---|---|---|---|
| Custom Elements v1 | 67+ | 63+ | 10.1+ | Core component registration |
| Shadow DOM v1 | 53+ | 63+ | 10+ | Style encapsulation |
| ES Modules | 61+ | 60+ | 10.1+ | Import/export syntax |
| Constructable Stylesheets | 73+ | 101+ | 16.4+ | Used by Lit for style sharing |
| CSS Custom Properties | 49+ | 31+ | 9.1+ | Design token system |
| IntersectionObserver | 51+ | 55+ | 12.1+ | Infinite scroll, scroll spy |
| Clipboard API | 66+ | 63+ | 13.1+ | Copy button (code blocks) |
@media (scripting) | 120+ | 113+ | 17+ | Gates the pre-upgrade hide in base.css — degrades safely |
The scripting media query is the one entry newer than the baseline, and
deliberately not a requirement. It gates the rule that hides components until they
upgrade; where unsupported, the query doesn't match and the hide switches off —
older browsers get a brief flash of unstyled content, never hidden content. See
Without JavaScript.
Polyfills
Evergreen browsers need no polyfills. For older browsers, @webcomponents/webcomponentsjs provides Custom Elements and Shadow DOM. Load it before any ARC UI imports:
Node.js
The build tooling and development server require Node.js 24+ (LTS)
and pnpm 10+. These are enforced via the engines field in the root package.json.
See Also
- Getting Started — installation and setup
- Frameworks — framework-specific installation and usage