Docs — UseClassy

A Vite plugin that automatically rewrites conditional class attributes like class:hover or class:focus into standard utility classes usable by Tailwind CSS and UnoCSS. UseClassy lets you write cleaner, more maintainable variant styles in your HTML, Vue, React, Blade, and Svelte code, with no runtime overhead.

html

<button  class="@container rounded px-4 bg-blue-600 text-white"  class:hover="bg-blue-700"  class:focus="ring-2 ring-blue-300"  class:@md="px-6"></button>

becomes class="@container rounded px-4 bg-blue-600 text-white hover:bg-blue-700 focus:ring-2 focus:ring-blue-300 @md:px-6". There is no runtime. Put UseClassy before Tailwind or UnoCSS so those engines see the rewritten utilities.

Install

bash

npm i -D vite-plugin-useclassynpx vite-plugin-useclassy init

init patches Vite and your CSS engine, plus VS Code IntelliSense for Tailwind. Run it from the app root (the folder with package.json and vite.config.*).

Option	Default	Notes
`--language`	`'vue'`	`'vue'` \| `'react'` \| `'blade'` \| `'svelte'`
`--engine`	auto-detect	`'tailwind'` \| `'unocss'`; Tailwind wins if both are installed
`--with-skills`	`false`	Agent skill, Cursor rules, and `AGENTS.md`
`--with-claude`	`false`	Also copy to `.claude/skills/` (requires `--with-skills`)
`--force`	`false`	Overwrite locally edited skill files
`--dry-run`	`false`	Print planned edits

If detection fails, follow the manual setup below.

Usage

Vue / HTML. Use class plus class:modifier:

vue

<button  class="px-4 py-2 rounded bg-blue-600 text-white"  class:hover="bg-blue-700 scale-105"  class:focus="ring-2 ring-blue-300"  class:disabled="opacity-50 cursor-not-allowed"  class:dark="bg-sky-700"/>

React. Use className and className:hover. JSX expressions work when the class tokens are string literals:

tsx

<button  className="px-4 py-2 rounded"  className:hover={isActive ? 'bg-blue-500 text-white' : 'bg-gray-200'}  className:@md="px-6"  className:group-hover/item="bg-red-500"  className:[&>*]="mt-2"  className:data-[state=open]="block"/>

Expressions with no string literals (className:hover={hoverClasses}) are left alone. Import types with import 'vite-plugin-useclassy/react' (or ClassyProps). React 18/19 is an optional peer, only needed for those helpers.

Quoted modifier values may use " or '. Prefer " in docs and new code.

className:@md, className:group-hover/item, and arbitrary variants like className:[&>*] / className:data-[state=open] use the same attribute spelling as Vue. UseClassy rewrites them before the JSX/HTML parser runs (bracket-aware so = inside […] stays part of the name). Put UseClassy before @vitejs/plugin-react. TypeScript and some linters may still flag the source the same way they already flag chained modifiers.

Svelte. Quoted modifiers transform; native directives do not. Put UseClassy before @sveltejs/vite-plugin-svelte.

svelte

<button class="px-4 py-2 rounded" class:hover="bg-blue-700" class:active={isActive}>

Laravel Blade. composer require useclassy/laravel, then language: "blade". PHP ^8.2, Laravel ^11–13. Blade files sit outside Vite’s module graph, so keep the class manifest registered with Tailwind or UnoCSS (below).

Chained modifiers

class:sm:hover="underline" emits sm:hover:underline only, the same composition as Tailwind / UnoCSS, not the individual sm: and hover: pieces.

Modifier names may include letters, digits, _, -, :, / (group-hover/item), @ (@md), and arbitrary variants with […] ([&>*], data-[state=open]). UseClassy parses modifier names with bracket depth so an = inside […] is not treated as the attribute separator. React uses the same modifier attributes as Vue; UseClassy rewrites them before JSX/HTML parse.

Vite

import useClassy from 'vite-plugin-useclassy'export default {  plugins: [    useClassy({      language: 'vue', // 'react' | 'blade' | 'svelte'      // engine: "unocss",    }),    // Tailwind / UnoCSS after UseClassy  ],}

Option	Default	Notes
`language`	`'vue'`	`'vue'` \| `'react'` \| `'blade'` \| `'svelte'`
`engine`	`'tailwind'`	`'unocss'` skips Tailwind `@source` inject
`outputDir` / `outputFileName`	`.classy` / `output.classy.html`	Class manifest Tailwind and Uno scan
`manifestRoot`	Vite `root`	Set when Vite’s root is a subfolder (e.g. Nuxt `srcDir: "app/"`)
`injectTailwindSource`	`true`	Tailwind v4 only; ignored for UnoCSS
`debug`	`false`	Log transform and manifest writes

Processes .vue, .svelte, .ts, .tsx, .js, .jsx, .html, and .blade.php. Skips node_modules, gitignored paths, and virtual modules.

Tailwind

UseClassy writes discovered utilities to .classy/output.classy.html (gitignored). Tailwind v4 does not scan gitignored files unless you @source them. The plugin injects that directive into stylesheets that @import "tailwindcss". init also writes it into your CSS.

css

@import 'tailwindcss';@source "./.classy/output.classy.html";

@source paths are relative to the CSS file. If the stylesheet lives in src/, use ../.classy/output.classy.html.

Tailwind v3. Add the manifest to content:

content: ["./.classy/output.classy.html"],

Path helpers: getUseClassyTailwindSourceDirective, getUseClassyTailwindV3ContentEntry from vite-plugin-useclassy or vite-plugin-useclassy/tailwind. Pass the same outputDir / outputFileName you use in the plugin.

UnoCSS

useClassy({ language: 'react', engine: 'unocss' })

Place it before unocss/vite. After the rewrite, Uno’s Vite pipeline already sees hover: classes. Register the HTML manifest as a filesystem source for files Uno does not extract (plain .ts / .js, Blade, HTML that never enter Vite):

import { defineConfig, presetUno } from 'unocss'import { getUseClassyUnoFilesystemEntry } from 'vite-plugin-useclassy/unocss'export default defineConfig({  presets: [presetUno()],  content: { filesystem: [getUseClassyUnoFilesystemEntry()] },})

UseClassy is variant-first (class:hover="bg-red"), not Attributify (bg="hover:..."). Don’t enable both on the same attributes. See demos/unocss-react.

IntelliSense

init merges this into .vscode/settings.json for Tailwind projects:

json

{  "tailwindCSS.classAttributes": ["class", "class:[\\w:/@\\[\\]\\-=&*>.]*", "className", "className:[\\w:/@\\[\\]\\-=&*>.]*"]}

Vue-only projects can omit the className entries. UnoCSS projects should use the UnoCSS VS Code extension instead.

Agent skill

bash

npx vite-plugin-useclassy init --with-skills

Path	Used by
`.agents/skills/useclassy/`	Cursor, Codex, Copilot
`.cursor/rules/useclassy-*.mdc`	Cursor
`AGENTS.md` (fenced block)	Windsurf, Aider, Cline, and others

Add --with-claude to also copy into .claude/skills/ (opt-in so Cursor doesn’t load the skill twice). Running it again is safe; --force overwrites local edits. Templates live in templates/.

Contributing

Issues and PRs welcome.

License

MIT