What is the difference between sizedbox and container ?

Overview

SizedBox

Container

SizedBox

Container

Key Differences

SizedBox — Simple Sizing & Spacing

dartCopy
// Fixed size box
SizedBox(
  width: 100,
  height: 50,
  child: ElevatedButton(onPressed: () {}, child: Text('OK')),
)

// Spacing between widgets
Column(
  children: [
    Text('Above'),
    SizedBox(height: 16), // vertical gap
    Text('Below'),
  ],
)

// Expand to fill parent
SizedBox.expand(
  child: Container(color: Colors.blue),
)

// Shrink to smallest possible size
SizedBox.shrink()

Container — Multi-Purpose Box

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Container(
  width: 200,
  height: 100,
  margin: EdgeInsets.all(8),
  padding: EdgeInsets.symmetric(horizontal: 16, vertical: 8),
  alignment: Alignment.center,
  decoration: BoxDecoration(
    color: Colors.blue,
    borderRadius: BorderRadius.circular(12),
    boxShadow: [BoxShadow(color: Colors.black26, blurRadius: 4)],
    border: Border.all(color: Colors.white, width: 2),
  ),
  child: Text('Hello', style: TextStyle(color: Colors.white)),
)

When to Use Which?

SizedBox

SizedBox

SizedBox.shrink()

Container

Container

Container

Container

Performance Tip

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// ✅ Prefer SizedBox for simple gaps
SizedBox(height: 16)

// ❌ Avoid Container when only spacing is needed
Container(height: 16) // unnecessary overhead

Rule: Always use

textCopy

SizedBox

for pure sizing/spacing — it is lighter. Use

textCopy

Container

only when you need decoration, padding, or alignment.