CSS Flexbox Generator

What is CSS Flexbox?

CSS Flexbox (Flexible Box Layout) is a one-dimensional layout model that lets a container control the size, direction, and alignment of its children. One-dimensional means Flexbox works along a single axis at a time — either a row or a column — giving you precise control over how items flow in that direction. When you need to control rows and columns simultaneously, CSS Grid is the better tool; in practice you'll often use both: Grid for the overall page structure, Flexbox for the components within it.

Set display: flex on a parent element and it becomes a flex container — its direct children become flex items that respond to the container's rules. Use display: inline-flex when you need the container itself to behave like an inline element while still using flexbox internally. Flexbox is supported in every modern browser (Chrome, Firefox, Safari, Edge) without vendor prefixes and has been baseline available since 2017.

How to use this generator

Start with a preset to get a working layout instantly, then fine-tune from there. The Container tab controls the parent element: set the main axis with flex-direction, distribute space along that axis with justify-content, and align items on the perpendicular axis with align-items. Switch to the Items tab to configure individual children — click any numbered box in the preview to jump straight to that item. Toggle between All and Changed in the code panel to see either the complete snapshot or only the properties you've modified.

Key flexbox properties explained

• flex-direction — Sets the main axis: row (left-to-right), row-reverse, column (top-to-bottom), or column-reverse. Everything else — justify-content, align-items, flex-basis — is relative to this axis.
• justify-content — Distributes free space along the main axis. space-between pushes items to the edges; center groups them in the middle; space-evenly adds equal gaps all around. Note: when this property distributes all available space, flex-grow has no effect.
• align-items — Aligns items on the cross axis (perpendicular to the main axis) within a single flex line. stretch fills the container height; center centers vertically in row mode; baseline aligns text baselines across items of different sizes.
• flex-wrap — Controls whether items overflow onto new lines. nowrap forces everything onto one line (items may shrink or overflow); wrap enables multi-line layouts. Enabling wrap also activates align-content, which controls spacing between the lines.
• gap — Adds consistent space between flex items without using margins. Works uniformly between all pairs of adjacent items.
• flex-grow — Defines how much a child expands when extra space is available. 0 means no growth; 1 on all items divides remaining space equally; 2 on one item gives it twice the share of a 1 neighbour.
• flex-shrink — Controls how a child shrinks when the container is too small. 1 (default) lets items shrink proportionally; 0 prevents shrinking entirely. Only active when flex-wrap: nowrap.
• flex-basis — Sets the initial size before the grow/shrink calculation runs. Behaves like width in row mode and height in column mode. Setting flex-basis: 0 with flex-grow: 1 makes items share all available space equally, regardless of content.
• align-self — Overrides the container's align-items value for a single flex item. Useful when one child needs to break out of the cross-axis alignment applied to all its siblings — for example, pinning one card to the bottom of a row while the others stretch.
• order — Changes the visual rendering order of items without altering DOM order. All items default to 0; items with a lower value appear first, higher values appear last. Negative values are valid. Note that reordering with order is purely visual — keyboard navigation and screen readers still follow the DOM order, so use this carefully in accessible interfaces.

align-content vs align-items

align-items aligns items within a single flex line. align-content distributes space between multiple flex lines — it only has an effect when flex-wrap is wrap or wrap-reverse and there is more than one line. Think of it like justify-content but for the cross axis at the line level.

A common gotcha: setting align-content on a flex container that uses flex-wrap: nowrap (the default) produces no visible effect — the property is silently ignored because there is only ever one line. If you set align-content and nothing changes, check that wrapping is enabled and that your container actually has enough items to overflow onto multiple lines. The align-content control in this generator is greyed out for exactly this reason — it only activates when wrap is on.