Flexbox Gap Indicator in Chrome DevTools

The purple dashed line area that appears in Chrome DevTools when inspecting elements is a visual indicator of available space within a flex container. This helpful feature shows the "remaining space" or "gap" where flex items could potentially expand.

What the Purple Dashed Area Represents

The purple dashed line indicates unused space within a flex container that could be occupied by flex items if they were to grow or expand. This visual cue helps developers understand:

• Available expansion space: How much room flex items have to grow
• Layout efficiency: Whether your flex container space is being utilized effectively
• Flex behavior: How flex-grow and flex-shrink properties might affect the layout

INFO

This feature is specific to Chrome/Chromium-based browsers' DevTools and appears when you inspect elements with flexbox layout.

Visual Example

When you have a flex item with minimal content, the purple area shows significant available space:

As you add more content to the flex item, the purple area decreases accordingly:

Practical Demonstration

Try this code example to see the purple dashed area in action:

CSS

*, html, body {
    box-sizing: border-box;
    margin: 0;
}

div {
    position: relative;
    background-color: lightgreen;
}

button {
  display: flex;
  width: 100px;
}

HTML

<div>
    <button>1</button>
</div>

Open Chrome DevTools and inspect the button element to see the purple dashed area indicating the available space where the element could expand.

Common Scenarios

Empty Table Cells

WARNING

When you see this purple area at the end of a table, check for empty cells. Empty table cells may not expand to the full available width but still occupy their assigned space, resulting in the purple indicator.

Percentage-Based Layouts

If you have a container with 100% width containing elements that don't fully utilize that space (for example, one div at 50% width and another at 40%), the remaining 10% of space will be shown as the purple dashed area.

Developer Benefits

This visual indicator helps with:

• Debugging flex layouts: Quickly identify unused space in flex containers
• Responsive design: Understand how elements might expand on different screen sizes
• Layout optimization: Spot opportunities to better utilize available space

TIP

Use this feature alongside Chrome DevTools' flexbox debugging tools to master CSS flexbox layouts and create more efficient container arrangements.