Semantic UI

The UI Framework for the AI Era

Agents write it. Browsers run it. Humans read it.

A web component framework with signals, expressive templates, and an off-the-shelf UI kit. No build step from generation to execution.

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Component Authoring

Expressive Templates

Author components using a signals based templating engine. Updates are surgical without full component rerenders.

  • Use js style expression to handle complexity.
  • Use lisp style expression to improve legibility and semantic intent.
  • Mix syntaxes to get the best of both worlds
Templating Guide

Designed for Agents

Specs as Code Contracts

Every component ships with a machine-readable spec. Agents read structured contracts to know exactly what's valid, what attributes compose, and what's appropriate.

  • Types, variations, and states with natural language descriptions
  • usageLevel tells agents what's common vs. niche — no hallucinated <ui-button instagram> in a checkout flow
  • Specs are a code contract that also inform usage patterns
Component Specs

No Build Required

Runtime Components

Define reactive web components with signals, Shadow DOM, and lifecycle hooks. Templates compile in the browser in under a millisecond — no bundler, no transpiler, no waiting.

  • Signals-based state with built-in helpers — toggle(), increment(), push()
  • Shadow DOM scoping — .primary just works, no prefixes or modules
  • Ship as standard ESM — works in any agent sandbox, CDN, or import map
Component Guide
Designed for Agents
Components are powered by machine readable specs designed to translate from natural language to code.
No Build Necessary
Signals, JSX style expression evaluation, and modern ESM running directly in the browser powered by web components.
Complete UI Library
A complete UI framework designed for compositionality and human in the loop editing. JIT Client-Side Tailwind inside Web Components too.

See It In Action