Why arbitrary values exist in Tailwind - See It in Action

Understanding Why Arbitrary Values Exist in Tailwind CSS

📖 Scenario: You are building a simple webpage where you want to style a box with a custom width and background color that are not part of Tailwind's default options.

🎯 Goal: Create a box using Tailwind CSS that uses arbitrary values for width and background color to demonstrate how you can customize styles beyond the default Tailwind classes.

📋 What You'll Learn

Use Tailwind CSS to style a <div> element

Set the width of the box to exactly 18rem using an arbitrary value

Set the background color of the box to exactly #4a90e2 using an arbitrary value

Add some padding and rounded corners using standard Tailwind classes

Ensure the box is centered horizontally on the page

💡 Why This Matters

🌍 Real World

Web developers often need to apply styles that are not included in Tailwind's default set. Arbitrary values let them do this quickly without writing custom CSS.

💼 Career

Knowing how to use arbitrary values in Tailwind CSS is valuable for frontend developers to create unique designs while keeping code clean and maintainable.

1

Create the HTML structure with a <div> box

Write the basic HTML skeleton with a <div> element that will be styled later. The <div> should have a class box.

Tailwind

  
  
  Arbitrary Values Example
  


  
    
  

Hint

Start with a simple HTML page and add a <div> with class box inside the <body>.

2

Add a config variable for the box width using an arbitrary value

Add the Tailwind class w-[18rem] to the <div> with class box to set its width to exactly 18rem.

Tailwind

  
  
  Arbitrary Values Example
  


  
    
  

Hint

Use the square bracket syntax w-[18rem] to set a custom width in Tailwind.

3

Add an arbitrary background color using Tailwind

Add the Tailwind class bg-[#4a90e2] to the <div> with class box w-[18rem] to set its background color to exactly #4a90e2.

Tailwind

  
  
  Arbitrary Values Example
  


  
    
  

Hint

Use the square bracket syntax bg-[#4a90e2] to set a custom background color in Tailwind.

4

Add padding, rounded corners, and center the box horizontally

Add the Tailwind classes p-6, rounded-lg, and mx-auto to the <div> with class box w-[18rem] bg-[#4a90e2] to add padding, rounded corners, and center it horizontally on the page.

Tailwind

  
  
  Arbitrary Values Example
  


  
    
  

Hint

Add padding with p-6, rounded corners with rounded-lg, and center horizontally with mx-auto.

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