Flutter: Expanded, Flexible, and Spacer Compared

Expanded, Flexible, and Spacer are often confused with each other. They all belong to Flex-based layouts, but each one solves a different problem. Choosing the right one helps prevent overflow issues and keeps your UI under control.

Live Demo

You can try the Expanded widget in the interactive example below:

💡 If the example does not open, click the DartPad link to run it in a new tab.

Core Difference

• Expanded: Fills the remaining space tightly.
• Flexible: Uses the remaining space more loosely.
• Spacer: Creates empty space and does not hold content.

This topic is a direct answer for searches like "flutter expanded vs flexible" and "flutter spacer".

What Expanded Does

Expanded gives the remaining space in a Row or Column to its child.

Row(
  children: [
    Container(width: 50, color: Colors.red),
    Expanded(
      child: Container(color: Colors.blue),
    ),
  ],
)

What Flexible Does

Flexible allows the child to use available space without forcing it to fill everything.

Row(
  children: [
    Flexible(
      fit: FlexFit.loose,
      child: Container(color: Colors.green),
    ),
  ],
)

This is useful when the content should keep more of its natural size.

What Spacer Does

Spacer creates blank space only. It does not carry visible content.

Row(
  children: [
    Text('Left'),
    Spacer(),
    Text('Right'),
  ],
)

When Should You Use Each One?

• Use Expanded when the widget must fill the remaining space.
• Use Flexible when the widget should stay flexible but not necessarily stretch fully.
• Use Spacer when you only need empty space.

Practical Example: Form Row

Row(
  children: [
    const Icon(Icons.person),
    const SizedBox(width: 12),
    Expanded(
      child: TextField(
        decoration: const InputDecoration(
          hintText: 'Enter your name',
        ),
      ),
    ),
  ],
)

Here, Expanded is the correct choice because the input should use the remaining width.

Practical Example: Button Row

Row(
  children: [
    ElevatedButton(onPressed: () {}, child: const Text('Cancel')),
    const Spacer(),
    ElevatedButton(onPressed: () {}, child: const Text('Save')),
  ],
)

This is a clean way to push buttons to opposite ends.

Common Mistakes

• Using Expanded where Flexible would be more appropriate
• Treating Flexible and Expanded as identical
• Using Spacer as if it were a content widget
• Trying to use these widgets outside a Flex parent

Frequently Asked Questions

What is the biggest difference between Expanded and Flexible?

Expanded forces full use of the available space, while Flexible stays more relaxed.

Can I use Expanded instead of Spacer?

Sometimes yes, but Spacer is cleaner when you only need empty space.

Which one helps with overflow errors?

In the right context, Expanded and Flexible can reduce overflow by distributing space properly.

Summary

Understanding the difference between Expanded, Flexible, and Spacer is a core part of Flutter layout design. When used correctly, they reduce overflow problems and help you build cleaner, more professional interfaces.