CSS Grid

🤔 What is CSS Grid?

CSS Grid is a two-dimensional layout system. Unlike Flexbox (which works in one direction at a time), Grid handles rows and columns simultaneously.

Think of it like a spreadsheet:

You define columns and rows
Each cell can hold content
Cells can span multiple columns or rows

.container {
  display: grid;
  grid-template-columns: 200px 1fr 200px;
  grid-template-rows: auto 1fr auto;
  gap: 16px;
}

Result: A 3-column, 3-row layout with a 16px gap between all cells.

📐 Grid Rows × Columns

flowchart TB
    subgraph GridLayout[CSS Grid]
        direction LR
        subgraph Columns[3 Columns]
            C1[Col 1<br/>200px]
            C2[Col 2<br/>1fr - flexible]
            C3[Col 3<br/>200px]
        end
        subgraph Rows[3 Rows]
            R1[Row 1 - auto<br/>Header]
            R2[Row 2 - 1fr<br/>Main Content]
            R3[Row 3 - auto<br/>Footer]
        end
    end

    style GridLayout fill:#7c3aed,color:#fff
    style Columns fill:#3b82f6,color:#fff
    style Rows fill:#10b981,color:#fff

Key differences from Flexbox:

Feature	Flexbox	Grid
Dimensions	1D (row OR column)	2D (rows AND columns)
Best for	Small-scale layouts	Full-page layouts
Content-driven	Items control size	Container controls size

📝 Defining Grids

.container {
  display: grid;

  /* Fixed + flexible columns */
  grid-template-columns: 200px 1fr 200px;       /* 3 columns */
  grid-template-columns: repeat(3, 1fr);         /* 3 equal columns */
  grid-template-columns: 250px 1fr;              /* sidebar + content */

  /* Rows */
  grid-template-rows: auto 1fr auto;             /* header + content + footer */

  /* Gap (shorthand for row-gap + column-gap) */
  gap: 16px;
}

The fr unit — fractional unit. 1fr = one share of the available space:

grid-template-columns: 2fr 1fr 1fr;
/* 2 + 1 + 1 = 4 total fractions */
/* Column 1 gets 2/4 space, columns 2 & 3 get 1/4 each */

Result: Three columns — the first is twice as wide as the other two.

🎯 Placing Items

Grid items automatically fill cells in order, but you can place them explicitly:

.header {
  grid-column: 1 / 3;   /* start at col 1, end before col 3 = spans 2 columns */
  grid-row: 1;           /* stays in row 1 */
}

.sidebar {
  grid-column: 1;
  grid-row: 2 / 4;       /* spans rows 2-3 */
}

.main {
  grid-column: 2 / 4;    /* spans columns 2-3 */
  grid-row: 2;
}

.footer {
  grid-column: 1 / 4;    /* spans all columns */
  grid-row: 3;
}

Or use the shorthand:

.header {
  grid-area: 1 / 1 / 2 / 4; /* row-start / col-start / row-end / col-end */
}

Result: Header spans the top, sidebar on left spans full height, main content fills the rest, footer spans the bottom.

🔲 Grid Template Areas

The most intuitive way to define layouts — name your areas:

.layout {
  display: grid;
  grid-template-columns: 250px 1fr;
  grid-template-rows: auto 1fr auto;
  grid-template-areas:
    "header  header"
    "sidebar main"
    "footer  footer";
  gap: 16px;
  min-height: 100vh;
}

.header  { grid-area: header; }
.sidebar { grid-area: sidebar; }
.main    { grid-area: main; }
.footer  { grid-area: footer; }

<div class="layout">
  <header class="header">Header</header>
  <aside class="sidebar">Sidebar</aside>
  <main class="main">Main Content</main>
  <footer class="footer">Footer</footer>
</div>

Result: A complete page layout using named grid areas. Easy to read and rearrange.

🧩 Grid vs Flexbox — When to Use What

Use Flexbox when…	Use Grid when…
Items in a single row or column	Full-page layouts
Navigation bars	Dashboard layouts
Centering content	Card grids
Small components (buttons, toolbars)	Magazine-style layouts
Content dictates layout size	Container dictates layout size

They work great together:

/* Grid for the page layout */
.page {
  display: grid;
  grid-template-columns: 250px 1fr;
}

/* Flexbox inside a grid cell for the toolbar */
.toolbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

In Simple Words

CSS Grid is 2D — rows AND columns at the same time
Use grid-template-columns and grid-template-rows to define the structure
The fr unit shares space proportionally (like flex-grow)
grid-template-areas is the most readable way to design page layouts
Use Grid for page layout, Flexbox for components — they work best together
gap replaces margin hacks for spacing between cells