Tailwindcss

Tailwind CSS v4 Best Practices

CSS-Native Configuration

Tailwind v4 eliminates tailwind.config.js. All configuration lives in CSS using @theme:

@import "tailwindcss";

@theme {
    --color-brand: #3b82f6;
    --color-brand-dark: #1d4ed8;
    --font-display: "Inter", sans-serif;
    --breakpoint-3xl: 1920px;
    --ease-bounce: cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

• Define custom design tokens in @theme — they become available as utilities automatically (text-brand, font-display, etc.).
• Override or extend the default theme using CSS custom properties — no JavaScript needed.
• Content detection is automatic — remove any manual content arrays.

Setup

Vite

npm install tailwindcss @tailwindcss/vite

// vite.config.ts
import tailwindcss from "@tailwindcss/vite";

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

PostCSS

npm install tailwindcss @tailwindcss/postcss

// postcss.config.js
export default {
    plugins: {
        "@tailwindcss/postcss": {},
    },
};

CLI

npx @tailwindcss/cli -i input.css -o output.css

Updated Utility Names

v4 renames several utilities to align with CSS specifications:

The automated upgrade tool handles these: npx @tailwindcss/upgrade.

New Utilities and Features

Container Queries

First-class support without plugins:

<div class="@container">
    <div class="flex flex-col @md:flex-row @lg:grid @lg:grid-cols-3">
        <!-- responsive to container, not viewport -->
    </div>
</div>

3D Transforms

<div class="rotate-x-12 rotate-y-6 perspective-800">
    <!-- 3D spatial transforms -->
</div>

Expanded Gradients

Radial and conic gradients with interpolation control:

<div class="bg-radial from-blue-500 to-purple-500">...</div>
<div class="bg-conic from-red-500 via-yellow-500 to-red-500">...</div>
<div class="bg-linear-to-r from-blue-500 to-green-500 interpolate-hsl">...</div>

Entry/Exit Animations

@starting-style support for CSS-only transitions without JavaScript:

<div class="transition-opacity starting:opacity-0">
    <!-- animates in from opacity-0 -->
</div>

not-* Variant

Inverse styling:

<div class="not-last:mb-4">...</div>
<input class="not-disabled:hover:bg-blue-50" />

Inferred Arbitrary Values

Use bare values without the bracket syntax for common utilities:

<div class="grid-cols-15 mt-21 text-lg/9">...</div>

Theme Variables

v4 exposes all theme values as CSS custom properties. Access them anywhere in your CSS:

.custom-component {
    color: var(--color-brand);
    font-family: var(--font-display);
    padding: var(--spacing-4);
}

This makes Tailwind values available to non-Tailwind code, animations, and JavaScript without hardcoding values.

Dark Mode

@import "tailwindcss";

@custom-variant dark (&:where(.dark, .dark *));

Use dark: variant as before: bg-white dark:bg-gray-900.

Utility Patterns

Spacing and Layout

• Use spacing scale consistently (p-4, gap-6, mt-8) — avoid arbitrary values unless the design requires a one-off value.
• Use gap on flex/grid containers instead of margin on children.
• Prefer size-* for square elements (size-10 = w-10 h-10).

Typography

• Use the text-* scale for font sizes.
• Set line-height with the slash syntax: text-lg/7.
• Use tracking-* for letter-spacing and leading-* for standalone line-height.

Responsive Design

• Design mobile-first — base styles are mobile, use sm:, md:, lg: for larger breakpoints.
• Use container queries (@container / @md:) for component-level responsiveness.
• Prefer container queries over media queries for reusable components.

Colors

• v4 uses a modernized P3 color palette for vivid displays.
• Use opacity modifiers: bg-blue-500/50 for 50% opacity.
• Define semantic color tokens in @theme (--color-primary, --color-danger) rather than using raw palette colors directly.

Class Organization

Order classes logically — layout, sizing, spacing, typography, visual, state:

<div
    class="flex items-center gap-4 w-full p-4 text-sm font-medium text-gray-900 bg-white rounded-lg shadow-sm hover:shadow-md transition-shadow"
></div>

Use Prettier with prettier-plugin-tailwindcss to auto-sort classes consistently.

Migration from v3

1. Run npx @tailwindcss/upgrade — handles ~90% of changes automatically.
2. Replace tailwind.config.js with @theme directives in your CSS.
3. Update PostCSS config to use @tailwindcss/postcss or switch to @tailwindcss/vite.
4. Replace deprecated class names (see updated utilities table above).
5. Remove manual content configuration — v4 detects sources automatically.

Browser requirements: Safari 16.4+, Chrome 111+, Firefox 128+.