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

Write templates with full JavaScript expressions or natural language-style Lisp syntax. Signals surgically update only what changed — no virtual DOM diffing.

  • Full JavaScript in templates — ternaries, method calls, destructuring
  • NL-style Lisp syntax for cleaner AI generation and human readability
Templating Guide

Designed for Agents

Specs as Code Contracts

Every component ships with a machine-readable spec. Agents know what's valid, how things compose, and what's contextually appropriate — no hallucination.

  • Types, variations, and states with natural language descriptions
  • usageLevel tells agents what's common vs. niche
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 needed.

  • Signals with built-in helpers — toggle(), increment(), push()
  • Standard ESM — works in any agent sandbox, CDN, or import map
Component Guide
Templates Example
Specs Example
Components Example
Designed for Agents
Machine-readable specs translate natural language to valid, composable UI code.
No Build Necessary
Signals, expression evaluation, and modern ESM running directly in the browser.
Complete UI Library
A full component library with composable primitives and JIT Tailwind in Shadow DOM.

See It In Action

Card Search Temperature Converer Ball Simulation Spectrum Analyzer