Column stacking on mobile in Bootsrap

Introduction

Column stacking helps your website look good on small screens by placing columns one on top of another instead of side by side.

When you want your website to be easy to read on phones.

When you have multiple columns that look too small on narrow screens.

When you want to make sure buttons or images don't get squeezed on mobile.

When you want a simple layout on desktop but a vertical layout on mobile.

When you want to improve user experience for mobile visitors.

Syntax

Bootsrap

<div class="row">
  <div class="col-md-6 col-12">Column 1</div>
  <div class="col-md-6 col-12">Column 2</div>
</div>

Use col-md-6 to make columns side by side on medium and larger screens.

Use col-12 to make columns full width and stack on small screens.

Examples

Three columns side by side on large screens, stacked on mobile.

Bootsrap

<div class="row">
  <div class="col-lg-4 col-12">Column 1</div>
  <div class="col-lg-4 col-12">Column 2</div>
  <div class="col-lg-4 col-12">Column 3</div>
</div>

Two columns with different widths on small screens and stacked on extra small screens.

Bootsrap

<div class="row">
  <div class="col-sm-8 col-12">Wide column</div>
  <div class="col-sm-4 col-12">Narrow column</div>
</div>

Columns side by side on all screen sizes, no stacking.

Bootsrap

<div class="row">
  <div class="col-6">Half width always</div>
  <div class="col-6">Half width always</div>
</div>

Sample Program

This example uses Bootstrap classes to create two columns that sit side by side on medium and larger screens, but stack vertically on smaller screens like phones.

Bootsrap

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Bootstrap Column Stacking Example</title>
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
  <main class="container mt-4">
    <h1>Column Stacking on Mobile</h1>
    <p>Resize the browser window to see columns stack on small screens.</p>
    <div class="row border p-3">
      <div class="col-md-6 col-12 bg-primary text-white p-3">Column 1</div>
      <div class="col-md-6 col-12 bg-secondary text-white p-3">Column 2</div>
    </div>
  </main>
</body>
</html>

Important Notes

The stacking happens because col-12 makes columns full width on small screens.

Time complexity is not relevant here, but remember that responsive design improves user experience.

Common mistake: forgetting to add col-12 for small screens, so columns stay side by side and look cramped.

Summary

Use Bootstrap grid classes with different breakpoints to control column stacking.

col-12 makes columns stack on small screens.

Combine with larger breakpoint classes like col-md-6 for side-by-side on bigger screens.

Practice

1. What does the Bootstrap class col-12 do on mobile screens?

easy

A. Makes the column take full width and stack vertically

B. Makes the column take half width and stay side-by-side

C. Hides the column on mobile screens

D. Centers the column horizontally

Solution

1. Step 1: Understand col-12 meaning

   The class col-12 means the column will take all 12 parts of the grid, which is full width.

2. Step 2: Effect on mobile screens

   On small screens, columns with col-12 stack vertically because each takes full width.

3. Final Answer:

   Makes the column take full width and stack vertically -> Option A

4. Quick Check:

   col-12 = full width stack [OK]

Hint: Full width columns stack vertically on mobile with col-12 [OK]

Common Mistakes:

• Thinking col-12 means half width
• Assuming columns stay side-by-side on mobile
• Confusing col-12 with hiding columns

2. Which Bootstrap class combination makes two columns stack on mobile but sit side-by-side on medium screens?

easy

A. col-6 col-md-12

B. col-md-6 col-lg-12

C. col-6 col-lg-6

D. col-12 col-md-6

Solution

1. Step 1: Analyze mobile stacking

   col-12 makes columns full width on mobile, so they stack vertically.

2. Step 2: Analyze medium screen layout

   col-md-6 makes columns half width on medium screens, so they sit side-by-side.

3. Final Answer:

   col-12 col-md-6 -> Option D

4. Quick Check:

   Mobile stack = col-12, Medium side-by-side = col-md-6 [OK]

Hint: Use col-12 for mobile stack, col-md-6 for medium side-by-side [OK]

Common Mistakes:

• Reversing col-12 and col-md-6 classes
• Using col-6 on mobile which prevents stacking
• Ignoring breakpoint order in class names

3. Given this HTML snippet:

<div class='row'>
  <div class='col-12 col-md-4'>A</div>
  <div class='col-12 col-md-8'>B</div>
</div>

How will columns appear on a small mobile screen?

medium

A. Columns A and B stacked vertically, each full width

B. Columns A and B stacked vertically, widths 4/12 and 8/12

C. Only column A visible, column B hidden

D. Columns A and B side-by-side with widths 4/12 and 8/12

Solution

1. Step 1: Check mobile classes

   Both columns have col-12 which means full width on small screens, so they stack vertically.

2. Step 2: Check medium screen classes

   col-md-4 and col-md-8 apply only on medium and larger screens, so no effect on mobile.

3. Final Answer:

   Columns A and B stacked vertically, each full width -> Option A

4. Quick Check:

   Mobile uses col-12, so stacked full width [OK]

Hint: On mobile, col-12 stacks columns vertically regardless of col-md-* [OK]

Common Mistakes:

• Thinking col-md-* affects mobile layout
• Assuming side-by-side on mobile
• Confusing widths on small screens

4. You want two columns to stack on mobile but sit side-by-side on medium screens. You wrote:

<div class='row'>
  <div class='col-md-6'>Left</div>
  <div class='col-md-6'>Right</div>
</div>

Why do the columns NOT stack on mobile?

medium

A. Because col-md-6 applies to mobile screens too, so on mobile columns default to equal width side-by-side

B. Because you forgot to add col-12 to make columns full width on mobile

C. Because row class disables stacking on mobile

D. Because columns need col-sm-12 to stack on mobile

Solution

1. Step 1: Understand default column behavior

   Without col-* classes for small screens, columns try to share space equally side-by-side.

2. Step 2: Add col-12 for mobile stacking

   Adding col-12 makes columns full width on mobile, forcing vertical stacking.

3. Final Answer:

   You forgot to add col-12 to make columns full width on mobile -> Option B

4. Quick Check:

   Mobile stack needs col-12 class [OK]

Hint: Add col-12 for mobile stacking, col-md-6 for medium side-by-side [OK]

Common Mistakes:

• Assuming col-md-6 controls mobile layout
• Thinking row class prevents stacking
• Using col-sm-12 instead of col-12 for mobile

5. You want a layout with three columns that stack on mobile, show two columns side-by-side on tablets, and three columns side-by-side on desktops. Which class setup achieves this?

hard

A. col-12 col-sm-4 col-lg-4

B. col-6 col-md-4 col-lg-3

C. col-12 col-md-6 col-lg-4

D. col-12 col-md-4 col-lg-3

Solution

1. Step 1: Mobile stacking with full width

   col-12 makes columns full width on mobile, so they stack vertically.

2. Step 2: Two columns side-by-side on tablets

   col-md-6 means on medium screens (tablets), columns take half width, so two fit side-by-side.

3. Step 3: Three columns side-by-side on desktops

   col-lg-4 means on large screens (desktops), columns take 4/12 width, so three fit side-by-side.

4. Final Answer:

   col-12 col-md-6 col-lg-4 -> Option C

5. Quick Check:

   Mobile stack = col-12, Tablet 2 cols = col-md-6, Desktop 3 cols = col-lg-4 [OK]

Hint: Use col-12 mobile, col-md-6 tablet, col-lg-4 desktop for stacking [OK]

Common Mistakes:

• Using col-sm instead of col-md for tablets
• Choosing wrong column widths that don't add up
• Forgetting col-12 for mobile stacking