Why arbitrary values exist in Tailwind

Introduction

Arbitrary values let you use custom sizes or colors not in Tailwind's default list. This helps you make your design exactly how you want.

You want a color shade that Tailwind doesn't have.

You need a spacing size like 7.5rem, which is not in the default scale.

You want a border radius that is not one of Tailwind's preset options.

You want to try a font size that is between Tailwind's standard sizes.

You want to quickly test a style without changing Tailwind config.

Syntax

Tailwind

class="property-[value]"

Use square brackets [ ] to wrap your custom value.

Make sure to write the value exactly as CSS expects, including units like rem, px, %, etc.

Examples

Sets a background color to a custom hex code.

Tailwind

class="bg-[#1a2b3c]"

Adds a top margin of 3.5 rem units.

Tailwind

class="mt-[3.5rem]"

Gives a border radius of 12 pixels.

Tailwind

class="rounded-[12px]"

Sets the font size to 18 pixels.

Tailwind

class="text-[18px]"

Sample Program

This example shows a button with a custom background color, padding, and rounded corners using arbitrary values. When you hover, the background changes to another custom color.

Tailwind

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <title>Arbitrary Values Example</title>
  <script src="https://cdn.tailwindcss.com"></script>
</head>
<body class="flex items-center justify-center min-h-screen bg-gray-100">
  <button class="bg-[#ff6347] text-white px-[2.5rem] py-[1rem] rounded-[1.25rem] hover:bg-[#e5533d] transition">
    Custom Button
  </button>
</body>
</html>

Important Notes

Arbitrary values give you freedom but use them wisely to keep your design consistent.

Always include units like rem or px when needed, or the style might not work.

Check your browser's developer tools to see the applied styles and debug if needed.

Summary

Arbitrary values let you use any CSS value inside Tailwind classes.

They help you customize designs beyond Tailwind's default options.

Use square brackets and include proper units for your custom values.

Practice

1. Why do arbitrary values exist in Tailwind CSS?

easy

A. To allow using any custom CSS value beyond default Tailwind options

B. To restrict styling only to predefined Tailwind classes

C. To automatically generate animations

D. To replace JavaScript functionality

Solution

1. Step 1: Understand Tailwind's default options

   Tailwind provides many predefined classes but cannot cover every possible CSS value.

2. Step 2: Purpose of arbitrary values

   Arbitrary values let you write any CSS value inside square brackets to customize styles beyond defaults.

3. Final Answer:

   To allow using any custom CSS value beyond default Tailwind options -> Option A

4. Quick Check:

   Arbitrary values = custom CSS values [OK]

Hint: Think: Custom styles beyond presets use arbitrary values [OK]

Common Mistakes:

• Thinking arbitrary values limit styling
• Confusing arbitrary values with animations
• Believing arbitrary values replace JavaScript

2. Which of the following is the correct syntax to set a custom width of 450 pixels using Tailwind's arbitrary values?

easy

A. width-450

B. w-[450px]

C. w-450px

D. width-[450]

Solution

1. Step 1: Recall Tailwind arbitrary value syntax

   Arbitrary values use square brackets with the CSS value inside, e.g., w-[450px].

2. Step 2: Check each option

   Only w-[450px] uses square brackets and includes units correctly.

3. Final Answer:

   w-[450px] -> Option B

4. Quick Check:

   Correct syntax = w-[450px] [OK]

Hint: Remember: square brackets around full CSS value with units [OK]

Common Mistakes:

• Omitting square brackets
• Missing units like px
• Using dash instead of brackets

3. What will be the width of the div rendered by this code?

<div class="w-[30rem] bg-blue-500 text-white p-4">Hello</div>

medium

A. Default width with blue background

B. Width of 30px with blue background

C. Width of 30rem (about 480px) with blue background

D. Width of 30rem but no background color

Solution

1. Step 1: Interpret the class w-[30rem]

   This sets the width to exactly 30rem, which is about 480 pixels (1rem ≈ 16px).

2. Step 2: Check other classes

   bg-blue-500 sets a blue background, text-white sets white text, and p-4 adds padding.

3. Final Answer:

   Width of 30rem (about 480px) with blue background -> Option C

4. Quick Check:

   Arbitrary width 30rem + blue bg = Width of 30rem (about 480px) with blue background [OK]

Hint: Remember rem units scale with root font size (~16px) [OK]

Common Mistakes:

• Confusing rem with px
• Ignoring background color class
• Assuming default width

4. Identify the error in this Tailwind class usage:

<div class="h-[100] bg-red-400">Error</div>

medium

A. Missing units inside the arbitrary value brackets

B. Incorrect use of square brackets

C. bg-red-400 is not a valid Tailwind class

D. Height cannot be set with arbitrary values

Solution

1. Step 1: Check the arbitrary value syntax

   The height is set as h-[100] but lacks units like px or rem.

2. Step 2: Understand CSS requirements

   CSS requires units for length values unless it's zero; so 100 alone is invalid.

3. Final Answer:

   Missing units inside the arbitrary value brackets -> Option A

4. Quick Check:

   Units required inside brackets [OK]

Hint: Always include units like px or rem inside brackets [OK]

Common Mistakes:

• Forgetting units inside arbitrary values
• Thinking brackets are wrong syntax
• Assuming Tailwind classes are invalid

5. You want to create a button with a custom border radius of 12px and a padding of 1.25rem using Tailwind. Which class combination correctly uses arbitrary values to achieve this?

hard

A. rounded-12px p-1.25rem

B. rounded-12 p-1.25rem

C. rounded-[12] p-[1.25]

D. rounded-[12px] p-[1.25rem]

Solution

1. Step 1: Use square brackets for arbitrary values

   Custom values must be inside square brackets with units, e.g., rounded-[12px] and p-[1.25rem].

2. Step 2: Check each option

   Only rounded-[12px] p-[1.25rem] correctly uses brackets and includes units for both border radius and padding.

3. Final Answer:

   rounded-[12px] p-[1.25rem] -> Option D

4. Quick Check:

   Arbitrary values need brackets + units [OK]

Hint: Use brackets and units for all custom CSS values [OK]

Common Mistakes:

• Omitting brackets
• Leaving out units
• Mixing syntax without brackets