@apply for extracting patterns in Tailwind

Introduction

@apply helps you reuse groups of Tailwind CSS classes by putting them into one custom class. This keeps your code neat and easy to change.

You want to use the same set of styles on many elements without repeating all classes.

You want to create a custom button style that you can reuse across your site.

You want to keep your HTML cleaner by moving complex class lists into CSS.

You want to update a style in one place and have it change everywhere.

You want to organize your styles better when your project grows.

Syntax

Tailwind

.custom-class {
  @apply utility-classes;
}

Use @apply inside a CSS or Tailwind CSS file.

You list the Tailwind utility classes you want to combine after @apply.

Examples

This creates a btn class with blue background, white bold text, padding, and rounded corners.

Tailwind

.btn {
  @apply bg-blue-500 text-white font-bold py-2 px-4 rounded;
}

This makes a card class with shadow, padding, white background, and rounded corners.

Tailwind

.card {
  @apply shadow-lg p-6 bg-white rounded-lg;
}

This defines an alert style with red background, border, text, padding, and rounded edges.

Tailwind

.alert {
  @apply bg-red-100 border border-red-400 text-red-700 px-4 py-3 rounded;
}

Sample Program

This example shows a button using a custom btn-primary class. The class uses @apply to combine Tailwind utilities for background color, text color, font weight, padding, rounded corners, and a hover effect.

The button is centered on the page with a light gray background.

Tailwind

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <title>@apply Example</title>
  <script src="https://cdn.tailwindcss.com"></script>
  <style>
    .btn-primary {
      @apply bg-blue-600 text-white font-semibold py-2 px-4 rounded hover:bg-blue-700;
    }
  </style>
</head>
<body class="flex items-center justify-center min-h-screen bg-gray-100">
  <button class="btn-primary" aria-label="Primary action button">Click Me</button>
</body>
</html>

Important Notes

You must use @apply inside a CSS file processed by Tailwind's build tool.

Not all Tailwind utilities can be used with @apply (for example, arbitrary value utilities like w-[100px] or certain complex utilities).

Using @apply helps keep your HTML cleaner and your styles consistent.

Summary

@apply lets you combine Tailwind classes into one custom class.

It helps reuse styles and keep your code tidy.

You write @apply inside CSS to extract patterns from utility classes.

Practice

1. What is the main purpose of using @apply in Tailwind CSS?

easy

A. To create animations in Tailwind CSS

B. To add JavaScript functionality to Tailwind classes

C. To import external CSS files into Tailwind

D. To combine multiple utility classes into one reusable custom class

Solution

1. Step 1: Understand what @apply does

   @apply lets you write multiple Tailwind utility classes inside a CSS rule to create a single custom class.

2. Step 2: Identify the main use

   This helps reuse styles and keep code tidy by combining utilities into one class.

3. Final Answer:

   To combine multiple utility classes into one reusable custom class -> Option D

4. Quick Check:

   @apply combines utilities = C [OK]

Hint: Remember: @apply bundles utilities into one class [OK]

Common Mistakes:

• Thinking @apply adds JavaScript
• Confusing @apply with animation creation
• Assuming @apply imports CSS files

2. Which of the following is the correct syntax to use @apply inside a CSS file?

easy

A. .btn { @apply text-white bg-blue-500 px-4 py-2; }

B. .btn { apply: text-white bg-blue-500 px-4 py-2; }

C. .btn { @use text-white bg-blue-500 px-4 py-2; }

D. .btn { apply(@text-white, @bg-blue-500); }

Solution

1. Step 1: Recall the correct @apply syntax

   The correct way is to write @apply followed by utility classes inside a CSS rule block.

2. Step 2: Check each option

   Only .btn { @apply text-white bg-blue-500 px-4 py-2; } uses @apply correctly with utility classes separated by spaces.

3. Final Answer:

   .btn { @apply text-white bg-blue-500 px-4 py-2; } -> Option A

4. Quick Check:

   Correct @apply syntax = A [OK]

Hint: Look for '@apply' keyword followed by utilities inside braces [OK]

Common Mistakes:

• Using 'apply:' instead of '@apply'
• Using '@use' or other incorrect keywords
• Trying to call @apply like a function

3. Given this CSS code using @apply:

.card {
  @apply p-6 bg-white rounded-lg shadow-md;
}

What visual styles will the .card class have?

medium

A. No padding, transparent background, rounded corners, and large shadow

B. Padding of 6px, black background, square corners, and no shadow

C. Padding of 1.5rem, white background, rounded corners, and medium shadow

D. Padding of 6rem, gray background, rounded corners, and small shadow

Solution

1. Step 1: Understand each utility class

   p-6 means padding 1.5rem, bg-white sets white background, rounded-lg adds large rounded corners, shadow-md adds medium shadow.

2. Step 2: Match these styles to options

   Padding of 1.5rem, white background, rounded corners, and medium shadow correctly describes these styles. Others have wrong padding sizes or colors.

3. Final Answer:

   Padding of 1.5rem, white background, rounded corners, and medium shadow -> Option C

4. Quick Check:

   p-6 + bg-white + rounded-lg + shadow-md = A [OK]

Hint: Know Tailwind spacing and color names to decode @apply output [OK]

Common Mistakes:

• Confusing padding units (px vs rem)
• Mixing up background colors
• Misunderstanding shadow sizes

4. What is wrong with this CSS using @apply?

.btn {
  @apply text-white bg-blue-500 px-4 py-2;
  @apply rounded-lg;
  color: red;
}

medium

A. The syntax is invalid because @apply must be last

B. Multiple @apply statements should be combined into one

C. The color property conflicts with @apply and causes error

D. You cannot use @apply with padding classes

Solution

1. Step 1: Check usage of multiple @apply

   Tailwind allows multiple @apply but best practice is to combine them for clarity and to avoid duplication.

2. Step 2: Analyze other options

   @apply works with padding, color property is valid CSS and does not cause error, and @apply can be anywhere inside the rule.

3. Final Answer:

   Multiple @apply statements should be combined into one -> Option B

4. Quick Check:

   Combine @apply classes for cleaner CSS = D [OK]

Hint: Combine all utilities in one @apply for neat CSS [OK]

Common Mistakes:

• Thinking @apply can't be used multiple times
• Assuming color property conflicts with @apply
• Believing @apply must be last in CSS block

5. You want to create a reusable button style in Tailwind using @apply that has white text, blue background, padding, rounded corners, and a hover effect that darkens the background. Which CSS snippet correctly achieves this?

hard

A. .btn {
@apply text-white bg-blue-500 px-4 py-2 rounded;
&:hover { @apply bg-blue-700; }
}

B. .btn {
@apply text-white bg-blue-500 px-4 py-2 rounded hover:bg-blue-700;
}

C. .btn {
@apply text-white bg-blue-500 px-4 py-2 rounded;
:hover { @apply bg-blue-700; }
}

D. .btn {
@apply text-white bg-blue-500 px-4 py-2 rounded;
hover: { @apply bg-blue-700; }
}

Solution

1. Step 1: Understand hover styling with @apply

   To apply hover styles with @apply, you must nest inside a CSS hover selector like &:hover in your CSS.

2. Step 2: Check each option's hover syntax

   .btn { @apply text-white bg-blue-500 px-4 py-2 rounded; &:hover { @apply bg-blue-700; } } correctly uses &:hover { @apply bg-blue-700; }. .btn { @apply text-white bg-blue-500 px-4 py-2 rounded hover:bg-blue-700; } tries to use hover:bg-blue-700 inside @apply which is invalid. Options C and D have incorrect hover selector syntax.

3. Final Answer:

   .btn { @apply text-white bg-blue-500 px-4 py-2 rounded; &:hover { @apply bg-blue-700; } } -> Option A

4. Quick Check:

   Use &:hover with @apply for hover styles = B [OK]

Hint: Use &:hover { @apply ... } for hover styles in CSS [OK]

Common Mistakes:

• Trying to use hover: prefix inside @apply
• Using :hover without & in nested CSS
• Incorrect hover selector syntax causing errors