tailwindcss

# Tailwind CSS v4 Development Guidelines

Best practices for using Tailwind CSS v4 utility classes effectively.

**Note**: Tailwind CSS v4 (released January 2025) uses a CSS-first configuration approach. If you need v3 compatibility, tailwind.config.js is still supported.

## Core Principles

1. **Utility-First**: Use utility classes instead of custom CSS
2. **Mobile-First**: Design for mobile, then scale up with responsive modifiers
3. **Component Extraction**: Extract repeated patterns into components
4. **Consistent Spacing**: Use Tailwind's spacing scale
5. **Custom Configuration**: Extend the default theme for brand consistency

## Basic Utilities

### Layout

```tsx
// Flexbox
<div className="flex items-center justify-between gap-4">
  <div className="flex-1">Content</div>
  <div className="flex-shrink-0">Sidebar</div>
</div>

// Grid
<div className="grid grid-cols-3 gap-4">
  <div>1</div>
  <div>2</div>
  <div>3</div>
</div>

// Positioning
<div className="relative">
  <div className="absolute top-0 right-0">Badge</div>
</div>
```

### Spacing

```tsx
// Padding and Margin
<div className="p-4 m-2">           {/* padding: 1rem, margin: 0.5rem */}
<div className="px-6 py-4">        {/* padding-x: 1.5rem, padding-y: 1rem */}
<div className="mt-8 mb-4">        {/* margin-top: 2rem, margin-bottom: 1rem */}

// Space between children
<div className="space-y-4">        {/* margin-bottom on all but last child */}
  <div>Item 1</div>
  <div>Item 2</div>
</div>
```

### Typography

```tsx
<h1 className="text-4xl font-bold text-gray-900">Heading</h1>
<p className="text-base font-normal text-gray-600 leading-relaxed">
  Paragraph text with comfortable line height.
</p>
<span className="text-sm font-medium text-blue-600">Label</span>
```

### Colors

```tsx
// Text colors
<p className="text-gray-900 dark:text-gray-100">Text</p>

// Background colors
<div className="bg-blue-500 hover:bg-blue-600">Button</div>

// Border colors
<div className="border border-gray-300">Box</div>
```

## Responsive Design

### Breakpoints

```tsx
// Mobile-first responsive classes
<div className="w-full md:w-1/2 lg:w-1/3">
  {/* Full width on mobile, half on medium screens, third on large */}
</div>

<h1 className="text-2xl md:text-4xl lg:text-6xl">
  {/* Responsive text sizes */}
</h1>

<div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-4 gap-4">
  {/* Responsive grid */}
</div>
```

### Container

```tsx
<div className="container mx-auto px-4">
  {/* Centered container with horizontal padding */}
</div>

<div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">
  {/* Responsive container padding */}
</div>
```

## Component Patterns

### Button

```tsx
<button className="px-4 py-2 bg-blue-600 text-white font-medium rounded-md hover:bg-blue-700 focus:outline-none focus:ring-2 focus:ring-blue-500 focus:ring-offset-2 disabled:opacity-50 disabled:cursor-not-allowed transition-colors">
  Click me
</button>

// Variants
<button className="px-4 py-2 border border-gray-300 rounded-md hover:bg-gray-50">
  Secondary
</button>
```

### Card

```tsx
<div className="bg-white rounded-lg shadow-md overflow-hidden">
  <img src="/image.jpg" alt="" className="w-full h-48 object-cover" />
  <div className="p-6">
    <h2 className="text-xl font-semibold mb-2">Card Title</h2>
    <p className="text-gray-600">Card content goes here.</p>
  </div>
</div>
```

### Form Input

```tsx
<div className="space-y-2">
  <label htmlFor="email" className="block text-sm font-medium text-gray-700">
    Email
  </label>
  <input
    type="email"
    id="email"
    className="w-full px-3 py-2 border border-gray-300 rounded-md focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent"
    placeholder="you@example.com"
  />
  <p className="text-sm text-gray-500">We'll never share your email.</p>
</div>
```

## State Variants

### Hover, Focus, Active

```tsx
<button className="bg-blue-500 hover:bg-blue-600 active:bg-blue-700 focus:ring-2 focus:ring-blue-500">
  Interactive Button
</button>

<a href="#" className="text-blue-600 hover:text-blue-800 hover:underline">
  Link
</a>
```

### Group Hover

```tsx
<div className="group">
  <img src="/image.jpg" className="group-hover:opacity-75 transition-opacity" />
  <p className="group-hover:text-blue-600">Hover the container</p>
</div>
```

### Disabled

```tsx
<button className="disabled:opacity-50 disabled:cursor-not-allowed" disabled>
  Disabled Button
</button>
```

## Dark Mode

```css
/* Tailwind v4: Configure in app/globals.css */
@import "tailwindcss";

@media (prefers-color-scheme: dark) {
  /* Or use class-based: .dark */
}
```

```tsx
// Usage (same as v3)
<div className="bg-white dark:bg-gray-900 text-gray-900 dark:text-gray-100">
  <h1 className="text-gray-900 dark:text-white">Title</h1>
  <p className="text-gray-600 dark:text-gray-400">Description</p>
</div>
```

## Custom Styles

### Arbitrary Values

```tsx
<div className="top-[117px]">           {/* Custom top value */}
<div className="bg-[#1da1f2]">          {/* Custom color */}
<div className="grid-cols-[200px_1fr]"> {/* Custom grid template */}
```

### @apply Directive

```css
/* components/button.css */
.btn-primary {
  @apply px-4 py-2 bg-blue-600 text-white font-medium rounded-md;
  @apply hover:bg-blue-700 focus:outline-none focus:ring-2 focus:ring-blue-500;
  @apply disabled:opacity-50 disabled:cursor-not-allowed;
}
```

## Configuration

### Tailwind v4: CSS-First Configuration

```css
/* app/globals.css */
@import "tailwindcss";

@theme {
  /* Custom colors */
  --color-brand-50: #eff6ff;
  --color-brand-100: #dbeafe;
  --color-brand-900: #1e3a8a;

  /* Custom spacing */
  --spacing-128: 32rem;

  /* Custom fonts */
  --font-family-sans: 'Inter', sans-serif;

  /* Custom breakpoints */
  --breakpoint-3xl: 1920px;
}
```

### Tailwind v3 Config (Still Supported)

```javascript
// tailwind.config.js (optional in v4)
module.exports = {
  content: [
    './app/**/*.{js,ts,jsx,tsx,mdx}',
    './components/**/*.{js,ts,jsx,tsx,mdx}',
  ],
  theme: {
    extend: {
      colors: {
        brand: {
          50: '#eff6ff',
          100: '#dbeafe',
          900: '#1e3a8a',
        }
      },
      spacing: {
        '128': '32rem',
      },
      fontFamily: {
        sans: ['Inter', 'sans-serif'],
      },
    },
  },
  plugins: [
    require('@tailwindcss/forms'),
    require('@tailwindcss/typography'),
  ],
}
```

## Plugins

### Official Plugins

```bash
npm install @tailwindcss/forms
npm install @tailwindcss/typography
npm install @tailwindcss/aspect-ratio
npm install @tailwindcss/container-queries
```

```tsx
// @tailwindcss/forms
<input type="text" className="form-input rounded-md" />

// @tailwindcss/typography
<article className="prose lg:prose-xl">
  <h1>Article Title</h1>
  <p>Content...</p>
</article>
```

## Performance

### Automatic Content Detection

Tailwind v4 automatically detects and scans all template files - no `content` configuration needed.

### Build Performance

Tailwind v4 delivers 3.5x faster full builds (~100ms) compared to v3 using modern CSS features like `@property` and `color-mix()`.

**Browser Requirements**: Safari 16.4+, Chrome 111+, Firefox 128+

## Common Patterns

### Centered Content

```tsx
<div className="flex items-center justify-center min-h-screen">
  <div>Centered content</div>
</div>
```

### Sticky Header

```tsx
<header className="sticky top-0 z-50 bg-white border-b">
  <nav>Navigation</nav>
</header>
```

### Grid Layout

```tsx
<div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
  {posts.map(post => (
    <PostCard key={post.id} post={post} />
  ))}
</div>
```

### Truncate Text

```tsx
<p className="truncate">This text will be truncated with ellipsis if too long</p>
<p className="line-clamp-3">This text will show max 3 lines with ellipsis</p>
```

## Best Practices

1. **Use Consistent Spacing**: Stick to Tailwind's spacing scale
2. **Responsive by Default**: Always consider mobile-first design
3. **Extract Components**: Avoid repeating long class lists
4. **Use Theme Colors**: Define custom colors in config, not arbitrary values
5. **Leverage @apply Sparingly**: Prefer utility classes in JSX
6. **Enable Dark Mode**: Plan for dark mode from the start
7. **Use Plugins**: Leverage official plugins for common needs
8. **Optimize Production**: Ensure purge is configured correctly

## Additional Resources

For detailed information, see:
- [Utility Patterns](resources/utility-patterns.md)
- [Component Library](resources/component-library.md)
- [Configuration Guide](resources/configuration.md)