CSS Flexbox Generator

Configure a flex container visually with controls for direction, justification, alignment, wrapping, and gap, then watch a live preview update immediately. Add or remove child items, tweak flex-grow, flex-shrink, and flex-basis for each one, and use the preview to understand how layout decisions affect real boxes.

The generator produces both plain CSS and Tailwind-style utility output so you can move from experimentation to implementation quickly. It is useful for learning flexbox concepts, debugging spacing or alignment issues, and prototyping responsive interface layouts before touching production code.

Flexbox is a one-dimensional layout model that controls how items are distributed along a single axis — either horizontal (row) or vertical (column). While CSS Grid handles two-dimensional layouts, Flexbox excels at distributing space among items in a single direction, making it the go-to choice for navigation bars, card rows, form layouts, and component-level alignment.

The flex-direction property defines the main axis. Row (default) lays items left to right. Row-reverse reverses the order. Column stacks items top to bottom. Column-reverse stacks bottom to top. The cross axis is always perpendicular to the main axis.

Justify-content controls alignment along the main axis. Options include flex-start (pack to the start), flex-end (pack to the end), center (pack to the center), space-between (distribute evenly with no outer margins), space-around (distribute with equal space around each item), and space-evenly (distribute with equal space between and around items).

Align-items controls alignment along the cross axis. Options include stretch (default, fill the container), flex-start (align to the start), flex-end (align to the end), center (align to the center), and baseline (align by text baseline). Understanding this property is crucial for centering content vertically.

The gap property adds consistent spacing between flex items without adding margins to the items themselves. This is a significant improvement over the older margin-based spacing approach because gap only applies between items, not at the container edges, eliminating the need for negative margins or :last-child selectors.

Individual item properties — flex-grow, flex-shrink, and flex-basis — control how each item responds to available or constrained space. Flex-grow determines how much an item should grow relative to its siblings when there is extra space. Flex-shrink determines how much an item should shrink when space is insufficient. Flex-basis sets the initial size before growing or shrinking occurs. The shorthand flex property combines all three: flex: 1 1 auto is equivalent to flex-grow: 1, flex-shrink: 1, flex-basis: auto.

Common flexbox patterns: Centering an element both horizontally and vertically uses just three properties on the container: display: flex, justify-content: center, and align-items: center. A sticky footer uses flex-direction: column on the body with flex-grow: 1 on the main content area. Equal-height columns in a card layout come naturally with Flexbox since items stretch to the tallest by default.

Flexbox wrapping (flex-wrap: wrap) allows items to flow onto multiple lines when they exceed the container width. Combined with flex-basis on items, this creates responsive layouts that adapt to container size without media queries.