Tailwindcss Responsive

---
name: tailwindcss-responsive
description: "Use when applying responsive variants at different screen widths, defining a custom breakpoint, or building container-query-based components."
user-invocable: false
---

<objective>
Documents responsive design utilities in Tailwind CSS v4: the default breakpoint scale (`sm`/`md`/`lg`/`xl`/`2xl`), defining custom breakpoints via `@theme`, container queries (`@container`, `@md`, `@lg` container-relative variants), and the mobile-first authoring pattern (base styles first, larger-breakpoint overrides layered on top).
</objective>

# Responsive Design

## Default Breakpoints

| Variant | Size | CSS |
|---------|--------|-----|
| `sm:` | 40rem (640px) | `@media (width >= 40rem)` |
| `md:` | 48rem (768px) | `@media (width >= 48rem)` |
| `lg:` | 64rem (1024px) | `@media (width >= 64rem)` |
| `xl:` | 80rem (1280px) | `@media (width >= 80rem)` |
| `2xl:` | 96rem (1536px) | `@media (width >= 96rem)` |

## Custom breakpoint
```css
@theme {
  --breakpoint-3xl: 120rem;
}
/* Usage: 3xl:grid-cols-6 */
```

## Container Queries v4
```html
<div class="@container">
  <div class="@md:grid-cols-2 @lg:grid-cols-3">
    <!-- Responsive to container -->
  </div>
</div>
```

### Size containers (since v4.3)
`@container` creates an inline-size container; `@container-size` creates a size container so block-axis units (`cqb`, `cqh`) resolve. Name it with `@container-size/{name}`.
```html
<div class="@container-size">
  <div class="h-[50cqb]">
    <!-- Half the container's block size -->
  </div>
</div>
```

## Mobile-first
```html
<div class="text-sm md:text-base lg:text-lg">
  <!-- Small screens first -->
</div>
```