Master CSS Flexbox: A Complete Guide to Responsive Layouts

What is Flexbox?

CSS Flexbox (Flexible Box Layout) is a one-dimensional layout method that makes it incredibly easy to arrange items in rows or columns. It solves common layout challenges like centering content, creating equal-height columns, and distributing space between elements.

Getting Started: The Flex Container

To use Flexbox, you need a flex container (parent) and flex items (children).

CSSCopy
1.container {
2  display: flex; /* This creates a flex container */
3}

Essential Flex Container Properties

1. flex-direction

Controls the direction of flex items.

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1.container {
2  flex-direction: row;        /* Default: left to right */
3  flex-direction: column;     /* Top to bottom */
4  flex-direction: row-reverse; /* Right to left */
5  flex-direction: column-reverse; /* Bottom to top */
6}

2. justify-content

Aligns items along the main axis (horizontally by default).

CSSCopy
1.container {
2  justify-content: flex-start;    /* Default: items at start */
3  justify-content: center;        /* Center items */
4  justify-content: flex-end;      /* Items at end */
5  justify-content: space-between; /* Space between items */
6  justify-content: space-around;  /* Space around items */
7  justify-content: space-evenly;  /* Equal space everywhere */
8}

3. align-items

Aligns items along the cross axis (vertically by default).

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1.container {
2  align-items: stretch;    /* Default: stretch to fill */
3  align-items: flex-start; /* Align to top */
4  align-items: center;     /* Center vertically */
5  align-items: flex-end;   /* Align to bottom */
6}

4. flex-wrap

Controls whether items wrap to new lines.

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1.container {
2  flex-wrap: nowrap; /* Default: all items on one line */
3  flex-wrap: wrap;   /* Items wrap to new lines */
4}

Essential Flex Item Properties

1. flex-grow

Defines how much an item should grow relative to other items.

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1.item {
2  flex-grow: 1; /* Item will grow to fill available space */
3  flex-grow: 2; /* Item will grow twice as much as flex-grow: 1 items */
4}

2. flex-shrink

Defines how much an item should shrink when space is limited.

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1.item {
2  flex-shrink: 1; /* Default: item can shrink */
3  flex-shrink: 0; /* Item won't shrink */
4}

3. flex-basis

Sets the initial size of an item before free space is distributed.

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1.item {
2  flex-basis: 200px; /* Item starts at 200px wide */
3  flex-basis: 25%;   /* Item starts at 25% of container */
4}

4. flex (shorthand)

Combines flex-grow, flex-shrink, and flex-basis.

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1.item {
2  flex: 1;           /* flex-grow: 1, flex-shrink: 1, flex-basis: 0% */
3  flex: 1 0 200px;   /* grow: 1, shrink: 0, basis: 200px */
4}

Common Layout Patterns

Perfect Centering

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1.center-container {
2  display: flex;
3  justify-content: center;
4  align-items: center;
5  height: 100vh; /* Full viewport height */
6}

Equal-Width Columns

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1.equal-columns {
2  display: flex;
3}
4
5.column {
6  flex: 1; /* Each column takes equal space */
7}

Header, Content, Footer Layout

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1.page-container {
2  display: flex;
3  flex-direction: column;
4  min-height: 100vh;
5}
6
7.header, .footer {
8  flex-shrink: 0; /* Don't shrink */
9}
10
11.content {
12  flex: 1; /* Takes remaining space */
13}

Navigation Bar

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1.navbar {
2  display: flex;
3  justify-content: space-between;
4  align-items: center;
5  padding: 1rem;
6}
7
8.nav-links {
9  display: flex;
10  gap: 1rem;
11}

Card Layout

CSSCopy
1.card-container {
2  display: flex;
3  flex-wrap: wrap;
4  gap: 1rem;
5}
6
7.card {
8  flex: 1 1 300px; /* Grow, shrink, min-width 300px */
9}

Quick Reference Cheat Sheet

Pro Tips

1. Use gap for spacing instead of margins - it's cleaner and more predictable
2. Flex items are block-level by default, even if they're normally inline elements
3. align-items: center is your best friend for vertical centering
4. flex: 1 makes items grow to fill available space equally
5. Combine with CSS Grid for complex layouts - use Flexbox for one-dimensional layouts

Browser Support

Flexbox has excellent browser support (99%+ of users). Safe to use in all modern projects without prefixes.

Common Gotchas

• Margins don't collapse in flex containers
• float, clear, and vertical-align have no effect on flex items
• min-width: 0 may be needed for text overflow in flex items
• Flex items create their own stacking context

Practice Exercise

Try creating a responsive card layout:

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1.card-grid {
2  display: flex;
3  flex-wrap: wrap;
4  gap: 1rem;
5  padding: 1rem;
6}
7
8.card {
9  flex: 1 1 calc(33.333% - 1rem);
10  min-width: 250px;
11  padding: 1rem;
12  border: 1px solid #ddd;
13  border-radius: 8px;
14}

This creates a responsive grid that shows 3 cards per row on larger screens and stacks on smaller screens.

Bookmark this guide for quick reference whenever you need to create flexible, responsive layouts with CSS Flexbox!