Tailwind CSS v4 Best Practices

---

name: tailwind-v4

description: Tailwind CSS v4 with CSS-first configuration and design tokens. Use when setting up Tailwind v4, defining theme variables, using OKLCH colors, or configuring dark mode. Triggers on @theme, @tailwindcss/vite, oklch, CSS variables, --color-, tailwind v4.

---

# Tailwind CSS v4 Best Practices

Quick Reference

**Vite Plugin Setup**:

// vite.config.ts
import tailwindcss from '@tailwindcss/vite';
import { defineConfig } from 'vite';

export default defineConfig({
  plugins: [tailwindcss()],
});

**CSS Entry Point**:

/* src/index.css */
@import 'tailwindcss';

**@theme Inline Directive**:

@theme inline {
  --color-primary: oklch(60% 0.24 262);
  --color-surface: oklch(98% 0.002 247);
}

Key Differences from v3

| Feature | v3 | v4 |

|---------|----|----|

| Configuration | tailwind.config.js | @theme in CSS |

| Build Tool | PostCSS plugin | @tailwindcss/vite |

| Colors | rgb() / hsl() | oklch() (default) |

| Theme Extension | extend: {} in JS | CSS variables |

| Dark Mode | darkMode config option | CSS variants |

@theme Directive Modes

default (standard mode)

Generates CSS variables that can be referenced elsewhere:

@theme {
  --color-brand: oklch(60% 0.24 262);
}

/* Generates: :root { --color-brand: oklch(...); } */
/* Usage: text-brand → color: var(--color-brand) */

**Note**: You can also use `@theme default` explicitly to mark theme values that can be overridden by non-default @theme declarations.

inline

Inlines values directly without CSS variables (better performance):

@theme inline {
  --color-brand: oklch(60% 0.24 262);
}

/* Usage: text-brand → color: oklch(60% 0.24 262) */

reference

Inlines values as fallbacks without emitting CSS variables:

@theme reference {
  --color-internal: oklch(50% 0.1 180);
}

/* No :root variable, but utilities use fallback */
/* Usage: bg-internal → background-color: var(--color-internal, oklch(50% 0.1 180)) */

OKLCH Color Format

OKLCH provides perceptually uniform colors with better consistency across hues:

oklch(L% C H)

**Examples**:

--color-sky-500: oklch(68.5% 0.169 237.323);  /* Bright blue */
--color-red-600: oklch(57.7% 0.245 27.325);   /* Vibrant red */
--color-zinc-900: oklch(21% 0.006 285.885);   /* Near-black gray */

CSS Variable Naming

Tailwind v4 uses double-dash CSS variable naming conventions:

@theme {
  /* Colors: --color-{name}-{shade} */
  --color-primary-500: oklch(60% 0.24 262);

  /* Spacing: --spacing multiplier */
  --spacing: 0.25rem;  /* Base unit for spacing scale */

  /* Fonts: --font-{family} */
  --font-display: 'Inter Variable', system-ui, sans-serif;

  /* Breakpoints: --breakpoint-{size} */
  --breakpoint-lg: 64rem;

  /* Custom animations: --animate-{name} */
  --animate-fade-in: fade-in 0.3s ease-out;
}

No Config Files Needed

Tailwind v4 eliminates configuration files:

{
  "devDependencies": {
    "@tailwindcss/vite": "^4.0.0",
    "@types/node": "^22.0.0",
    "tailwindcss": "^4.0.0",
    "vite": "^6.0.0"
  }
}

Progressive Disclosure

Decision Guide

When to use @theme inline vs default

**Use `@theme inline`**:

**Use `@theme` (default)**:

When to use @theme reference

**Use `@theme reference`**:

Common Patterns

Two-Tier Variable System

Semantic variables that map to design tokens:

@theme {
  /* Design tokens (OKLCH colors) */
  --color-blue-600: oklch(54.6% 0.245 262.881);
  --color-slate-800: oklch(27.9% 0.041 260.031);

  /* Semantic mappings */
  --color-primary: var(--color-blue-600);
  --color-surface: var(--color-slate-800);
}

/* Usage: bg-primary, bg-surface */

Custom Font Configuration

@theme {
  --font-display: 'Inter Variable', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, monospace;

  --font-display--font-variation-settings: 'wght' 400;
  --font-display--font-feature-settings: 'cv02', 'cv03', 'cv04';
}

/* Usage: font-display, font-mono */

Animation Keyframes

@theme inline {
  --animate-beacon: beacon 2s ease-in-out infinite;

  @keyframes beacon {
    0%, 100% {
      opacity: 1;
      transform: scale(1);
    }
    50% {
      opacity: 0.5;
      transform: scale(1.05);
    }
  }
}

/* Usage: animate-beacon */