Creating custom utilities with addUtilities in Tailwind - Try It Yourself

Creating Custom Utilities with addUtilities in Tailwind CSS

📖 Scenario: You are building a simple webpage and want to add a custom utility class to Tailwind CSS to create a special button style that is not available by default.

🎯 Goal: Create a custom utility class called .btn-custom using Tailwind's addUtilities function. This class should add a background color of #4CAF50, white text color, some padding, and rounded corners. Then use this class in your HTML button.

📋 What You'll Learn

Create a Tailwind CSS plugin that adds a custom utility class .btn-custom

The .btn-custom class must have background-color: #4CAF50;

The .btn-custom class must have color: white;

The .btn-custom class must have padding: 0.5rem 1rem;

The .btn-custom class must have border-radius: 0.375rem;

Use the .btn-custom class in an HTML button element

💡 Why This Matters

🌍 Real World

Custom utilities let you extend Tailwind CSS to fit your unique design needs without writing extra CSS files.

💼 Career

Knowing how to create custom utilities with addUtilities is useful for frontend developers to maintain consistent design systems and speed up styling.

1

Set up the Tailwind CSS plugin file

Create a file called tailwind.config.js and inside it, import plugin from tailwindcss/plugin. Then create an empty plugin using plugin(function() {}) and export the config object with an empty plugins array.

Tailwind

const plugin = require('tailwindcss/plugin');

module.exports = {
  plugins: [
    // Your plugin will go here
  ],
};

// Your code here

Hint

Remember to import plugin from tailwindcss/plugin and export a config object with a plugins array.

2

Add the custom utility with addUtilities

Inside the plugins array, add a plugin created with plugin(function({ addUtilities }) { ... }). Use addUtilities to add a new utility class .btn-custom with these CSS properties: background-color: '#4CAF50', color: 'white', padding: '0.5rem 1rem', and border-radius: '0.375rem'.

Tailwind

const plugin = require('tailwindcss/plugin');

module.exports = {
  plugins: [
    plugin(function({ addUtilities }) {
      // Add your custom utilities here
    }),
  ],
};

// Your code here

Hint

Use addUtilities inside the plugin function to add the .btn-custom class with the specified CSS properties.

3

Create the HTML file with a button using the custom class

Create an index.html file with a basic HTML5 structure. Inside the <body>, add a <button> element with the class btn-custom and the text Click Me. Also link the Tailwind CSS stylesheet properly.

Tailwind

  
  
  Custom Button
  


  

Hint

Make sure to add the btn-custom class to the button and link the compiled Tailwind CSS file.

4

Build Tailwind CSS and verify the custom utility works

Run your Tailwind CSS build process to generate the CSS file (e.g., npx tailwindcss -i ./src/input.css -o ./dist/output.css --watch). Then open index.html in a browser and verify the button has a green background, white text, padding, and rounded corners from the btn-custom class.

Tailwind

  
  
  Custom Button
  


  Click Me
  



// Run Tailwind build command in terminal
// Your code here

Hint

Make sure to run the Tailwind build command and open the HTML file in a browser to see the green button with white text and rounded corners.

Practice

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

easy

A. To create custom CSS classes that can be reused in your HTML

B. To remove unused Tailwind CSS classes from the build

C. To automatically generate responsive breakpoints

D. To add JavaScript functionality to Tailwind components

Solution

1. Step 1: Understand the role of addUtilities

   addUtilities is used to define new CSS classes with custom styles that Tailwind does not provide by default.

2. Step 2: Compare with other options

   Options A, B, and D describe other Tailwind or unrelated features, not the purpose of addUtilities.

3. Final Answer:

   To create custom CSS classes that can be reused in your HTML -> Option A

4. Quick Check:

   addUtilities = create reusable custom classes [OK]

Hint: Remember: addUtilities adds new CSS classes [OK]

Common Mistakes:

• Confusing addUtilities with purge or remove features
• Thinking addUtilities adds JavaScript code
• Assuming it auto-generates responsive breakpoints

2. Which of the following is the correct syntax to add a custom utility class .text-shadow with text-shadow: 2px 2px #000; using addUtilities?

easy

A. addUtilities('.text-shadow { text-shadow: 2px 2px #000; }')

B. addUtilities({ '.text-shadow': { 'text-shadow': '2px 2px #000' } })

C. addUtilities({ textShadow: '2px 2px #000' })

D. addUtilities({ '.text-shadow': 'text-shadow: 2px 2px #000;' })

Solution

1. Step 1: Check the object format for addUtilities

   addUtilities expects an object where keys are class selectors and values are objects of CSS properties.

2. Step 2: Validate each option

   addUtilities({ '.text-shadow': { 'text-shadow': '2px 2px #000' } }) correctly uses an object with selector key and CSS property object value. Options B and D use incorrect formats (string or wrong value type). addUtilities({ textShadow: '2px 2px #000' }) misses the selector key.

3. Final Answer:

   addUtilities({ '.text-shadow': { 'text-shadow': '2px 2px #000' } }) -> Option B

4. Quick Check:

   addUtilities needs selector: CSS object [OK]

Hint: Use object with selector keys and CSS property objects [OK]

Common Mistakes:

• Passing CSS as a string instead of an object
• Omitting the selector key for the utility
• Using camelCase for CSS properties instead of kebab-case

3. Given this Tailwind plugin code snippet, what CSS class will be generated?

addUtilities({
  '.custom-border': {
    'border-width': '3px',
    'border-color': '#f00'
  }
})

medium

A. A class named .border-custom with 3px red border

B. A class named .custom-border with 1px black border

C. A class named .custom-border with 3px red border

D. No class will be generated due to syntax error

Solution

1. Step 1: Identify the class name and CSS properties

   The key '.custom-border' defines the class name. The CSS properties set border width to 3px and border color to red (#f00).

2. Step 2: Confirm no syntax errors

   The object syntax is correct, so the class will be generated as described.

3. Final Answer:

   A class named .custom-border with 3px red border -> Option C

4. Quick Check:

   Selector and CSS properties match output class [OK]

Hint: Class name is the object key, CSS inside is the style [OK]

Common Mistakes:

• Confusing class name with CSS property names
• Assuming default border width or color
• Thinking syntax error prevents generation

4. Identify the error in this Tailwind plugin code that tries to add a .bg-gradient utility:

addUtilities({
  '.bg-gradient': 'background: linear-gradient(to right, #000, #fff);'
})

medium

A. Missing semicolon after addUtilities call

B. Class selector should not start with a dot

C. The property name 'background' is invalid in Tailwind

D. CSS properties must be inside an object, not a string

Solution

1. Step 1: Check the value type for the class key

   The value for '.bg-gradient' must be an object with CSS properties, not a string.

2. Step 2: Validate other options

   Class selectors should start with a dot (correct here). 'background' is a valid CSS property. Semicolon after function call is optional in JavaScript.

3. Final Answer:

   CSS properties must be inside an object, not a string -> Option D

4. Quick Check:

   CSS properties need object format [OK]

Hint: Use object for CSS properties, not string [OK]

Common Mistakes:

• Passing CSS as a string instead of an object
• Removing the dot from class selector
• Thinking semicolon is mandatory after addUtilities

5. You want to create a custom utility .hover-scale that scales an element to 1.1 times its size on hover using addUtilities. Which is the correct way to add this utility with hover variant support?

hard

A. addUtilities({ '.hover-scale': { transform: 'scale(1.1)' } }, { variants: ['hover'] })

B. addUtilities({ '.hover-scale:hover': { transform: 'scale(1.1)' } })

C. addUtilities({ '.hover-scale': { ':hover': { transform: 'scale(1.1)' } } })

D. addUtilities({ '.hover-scale': { transform: 'scale(1.1)' } }, { variants: ['responsive'] })

Solution

1. Step 1: Understand how to add variants with addUtilities

   Variants like 'hover' are added as a second argument object with a variants array.

2. Step 2: Check each option's approach

   addUtilities({ '.hover-scale': { transform: 'scale(1.1)' } }, { variants: ['hover'] }) correctly adds the utility and enables hover variant. addUtilities({ '.hover-scale:hover': { transform: 'scale(1.1)' } }) incorrectly tries to put :hover in the selector key. addUtilities({ '.hover-scale': { ':hover': { transform: 'scale(1.1)' } } }) nests :hover inside CSS object, which is invalid. addUtilities({ '.hover-scale': { transform: 'scale(1.1)' } }, { variants: ['responsive'] }) uses 'responsive' variant, not hover.

3. Final Answer:

   addUtilities({ '.hover-scale': { transform: 'scale(1.1)' } }, { variants: ['hover'] }) -> Option A

4. Quick Check:

   Variants go in second argument as array [OK]

Hint: Add variants as second argument with variants array [OK]

Common Mistakes:

• Putting :hover inside selector string
• Nesting :hover inside CSS object
• Using wrong variant name like 'responsive' instead of 'hover'