Flexbox (Flexible Box Layout) is a one-dimensional layout method that excels at distributing space and aligning items in a container. It's perfect for component layouts, navigation bars, and any scenario where you need flexible, responsive arrangements.

Flex Container Basics

To create a flex container, apply display: flex:

.container {
  display: flex;
  /* or display: inline-flex; for inline containers */
}

Main Axis and Cross Axis

Understanding axes is crucial for Flexbox:

.container {
  display: flex;
  flex-direction: row; /* Main axis: horizontal, Cross axis: vertical */
  /* Other values: row-reverse, column, column-reverse */
}

Flex Container Properties

1. justify-content (Main Axis Alignment)

.container {
  display: flex;
  justify-content: flex-start; /* Default */
  /* Other values: flex-end, center, space-between, space-around, space-evenly */
}

/* Practical example: Navigation */
.nav {
  display: flex;
  justify-content: space-between;
  padding: 1rem;
  background: #2c3e50;
}

.nav-logo {
  font-weight: bold;
  color: white;
}

.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

2. align-items (Cross Axis Alignment)

.container {
  display: flex;
  align-items: stretch; /* Default */
  /* Other values: flex-start, flex-end, center, baseline */
}

/* Practical example: Card with icon */
.card {
  display: flex;
  align-items: center;
  padding: 1rem;
  background: white;
  border-radius: 8px;
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.card-icon {
  width: 48px;
  height: 48px;
  margin-right: 1rem;
}

Interactive Flexbox Example

Try this interactive flexbox card layout:

3. flex-wrap

.container {
  display: flex;
  flex-wrap: nowrap; /* Default */
  /* Other values: wrap, wrap-reverse */
}

/* Practical example: Tag list */
.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag {
  padding: 0.25rem 0.75rem;
  background: #3498db;
  color: white;
  border-radius: 20px;
  font-size: 0.875rem;
}

4. align-content (Multi-line Cross Axis)

.container {
  display: flex;
  flex-wrap: wrap;
  align-content: flex-start;
  /* Other values: flex-end, center, space-between, space-around, stretch */
  height: 300px;
}

5. gap (Spacing Between Items)

.container {
  display: flex;
  gap: 20px; /* Both row and column gap */
  /* Or separately: row-gap: 10px; column-gap: 20px; */
}

Flex Item Properties

1. flex-grow, flex-shrink, flex-basis

.item {
  flex-grow: 0;    /* Don't grow */
  flex-shrink: 1;  /* Can shrink */
  flex-basis: auto; /* Initial size */
  
  /* Shorthand */
  flex: 1; /* Equivalent to: flex: 1 1 0 */
}

/* Practical example: Sidebar layout */
.layout {
  display: flex;
  gap: 2rem;
  min-height: 100vh;
}

.sidebar {
  flex: 0 0 250px; /* Don't grow or shrink, fixed 250px */
  background: #ecf0f1;
  padding: 1rem;
}

.main-content {
  flex: 1; /* Take remaining space */
  padding: 1rem;
}

2. align-self (Individual Cross Axis Alignment)

.item {
  align-self: auto; /* Default - uses align-items value */
  /* Other values: flex-start, flex-end, center, baseline, stretch */
}

/* Practical example: Hero section */
.hero {
  display: flex;
  align-items: center;
  min-height: 400px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.hero-content {
  flex: 1;
  padding: 2rem;
  color: white;
}

.hero-image {
  flex: 1;
  align-self: stretch;
  object-fit: cover;
}

3. order (Visual Order)

.item {
  order: 0; /* Default */
  /* Negative values come first, positive values come last */
}

/* Practical example: Mobile-first layout */
.article {
  display: flex;
  flex-direction: column;
}

.article-content { order: 2; }
.article-sidebar { order: 1; }
.article-related { order: 3; }

@media (min-width: 768px) {
  .article {
    flex-direction: row;
  }
  
  .article-content { order: 1; flex: 2; }
  .article-sidebar { order: 2; flex: 1; }
  .article-related { order: 3; flex: 1; }
}

Common Flexbox Patterns

1. Centering Content

/* Perfect centering */
.center-container {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
}

/* Horizontal centering only */
.h-center {
  display: flex;
  justify-content: center;
}

/* Vertical centering only */
.v-center {
  display: flex;
  align-items: center;
}

2. Equal Height Columns

.columns {
  display: flex;
  gap: 2rem;
}

.column {
  flex: 1;
  padding: 1.5rem;
  background: #f8f9fa;
  border-radius: 8px;
  /* All columns will have equal height automatically */
}

3. Sticky Footer

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  margin: 0;
}

main {
  flex: 1; /* Takes all available space */
}

footer {
  background: #2c3e50;
  color: white;
  padding: 2rem;
  /* Always sticks to bottom */
}

4. Media Object

.media {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
}

.media-image {
  flex-shrink: 0;
  width: 100px;
  height: 100px;
  object-fit: cover;
  border-radius: 8px;
}

.media-content {
  flex: 1;
}

5. Responsive Navigation

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
  background: #2c3e50;
}

.nav-menu {
  display: flex;
  gap: 2rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-item a {
  color: white;
  text-decoration: none;
  transition: opacity 0.3s;
}

.nav-item a:hover {
  opacity: 0.8;
}

/* Mobile menu */
@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    left: -100%;
    top: 70px;
    flex-direction: column;
    background-color: #2c3e50;
    width: 100%;
    text-align: center;
    transition: 0.3s;
    padding: 2rem 0;
  }
  
  .nav-menu.active {
    left: 0;
  }
}

6. Card Grid with Flexbox

.card-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  padding: 2rem;
}

.card {
  flex: 1 1 300px; /* Grow, shrink, min-width 300px */
  display: flex;
  flex-direction: column;
  background: white;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
  transition: transform 0.3s;
}

.card:hover {
  transform: translateY(-4px);
}

.card-image {
  height: 200px;
  object-fit: cover;
}

.card-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  padding: 1.5rem;
}

.card-title {
  margin: 0 0 0.5rem;
  font-size: 1.25rem;
}

.card-description {
  flex: 1;
  color: #666;
  line-height: 1.6;
}

.card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid #eee;
}

Flexbox vs Grid

Use Flexbox when:

• Working with one-dimensional layouts
• Content size should determine layout
• You need alignment and distribution of space
• Building navigation bars, toolbars, or small components

Use Grid when:

• Working with two-dimensional layouts
• You need precise control over rows and columns
• Building complex page layouts
• You want to overlap items

Browser Support and Prefixes

Modern browsers fully support Flexbox, but for older browsers:

.container {
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  
  -webkit-box-pack: center;
  -webkit-justify-content: center;
  -ms-flex-pack: center;
  justify-content: center;
}

Flexbox has become an essential tool for modern web development. Master these concepts, and you'll be able to create flexible, responsive layouts with ease!