CSS Flexbox (Flexible Box Layout) is a one-dimensional layout model that lets you arrange elements in rows or columns. It gives you control over how items grow, shrink, and align within a container — making it much easier to build responsive layouts without floats or absolute positioning.

What is the difference between justify-content and align-items?

justify-content controls alignment along the main axis (horizontal when flex-direction is row, vertical when column), while align-items controls alignment along the cross axis (the perpendicular direction). For example, justify-content: center horizontally centers items in a row, and align-items: center vertically centers them.

When should I use flex-wrap?

Use flex-wrap: wrap when you want items to move to the next line if they don't all fit in the container, instead of overflowing. This is essential for responsive designs where content should reflow on smaller screens. flex-wrap: nowrap (the default) forces all items onto a single line.

What does align-content do?

align-content controls how multiple rows of flex items are distributed along the cross axis — but it only has effect when flex-wrap is set to wrap and there are multiple lines of items. If all items fit on one line, align-content has no visible effect.

How does the gap property work in Flexbox?

The gap property (formerly grid-gap) sets the space between flex items. It's a shorthand for row-gap and column-gap. Unlike margins, gap doesn't add space on the outer edges of the container — only between the items themselves. It's supported in all modern browsers.

CSSフレックスボックスジェネレーター

CSSフレックスボックスレイアウトを視覚的に設計し、生成されたCSSコードをコピーします。

コンテナプロパティ

flex-direction

flex-wrap

justify-content

align-items

align-content

gap

4 アイテム

プレビュー

Item 1

Item 2

Item 3

Item 4

生成されたCSS

.container {
  display: flex;
  flex-direction: row;
  flex-wrap: nowrap;
  justify-content: flex-start;
  align-items: stretch;
  align-content: stretch;
  gap: 8px;
}

使い方

CSSフレックスボックスレイアウトを視覚的に設計し、生成されたCSSコードをコピーします。

1Adjust the container properties: choose flex-direction, flex-wrap, justify-content, align-items, align-content, and gap.
2Watch the live preview update instantly as you change each property.
3Add or remove flex items using the Add Item / Remove Item buttons (up to 8 items).
4Copy the generated CSS from the output panel and paste it into your stylesheet.
5Click Reset to return all properties to their default values.

主な機能

Visual live preview showing colored flex items responding to every property change
Controls for all 6 key container properties: flex-direction, flex-wrap, justify-content, align-items, align-content, gap
Add up to 8 flex items to see how layouts behave with different item counts
One-click copy of the complete generated CSS ready to paste into your project

よくある質問

詳しく読む

CSS Flexbox Generator Guide — Build Layouts Visually