Container vs Item Properties in Flexbox
A flex container generator like this one produces two separate rule blocks because Flexbox properties split cleanly between parent and children. Container properties, display: flex, flex-direction, flex-wrap, justify-content, align-items, align-content, and gap, go on the parent element and control how its children are arranged as a group. Item properties, the flex shorthand, align-self, and order, go on the children themselves and can override the container's defaults for one specific item. Mixing these up, putting justify-content on a child or flex on the parent, is a common source of "why isn't this working" confusion.
How to Use This CSS Flexbox Generator
This flexbox css generator online sets Flex direction, Flex wrap, Justify content, Align items, Align content, and Gap to shape the container, then adjust the Container selector to match your actual markup. Toggle Include item CSS block on to also generate item-level rules: set the Item selector, Item flex (the flex shorthand, e.g. "1" or "1 1 200px"), Item align-self to override alignment for that item specifically, and Item order to change its visual position without touching the HTML. Enable Use inline-flex if you need an inline-level flex container instead of a block-level one. As a flexbox code generator built for real workflows, it copies cleanly: both generated rule blocks are ready to paste and apply to your actual selectors.
justify-content vs align-items: Main Axis vs Cross Axis
This justify content align items generator distinction comes down to which axis each property controls, and that axis flips depending on flex-direction. With row (the default), the main axis runs horizontally and justify-content controls horizontal spacing, while align-items controls vertical position. With column, that swaps entirely, justify-content controls vertical spacing and align-items controls horizontal position, the single most common source of "my alignment properties aren't doing what I expect" confusion in Flexbox.
| Property | Axis | Controls |
|---|---|---|
| justify-content | Main axis (row: horizontal, column: vertical) | Spacing and distribution of items along the main axis |
| align-items / align-self | Cross axis (row: vertical, column: horizontal) | Position of items along the cross axis |
Common Flexbox Mistakes This Tool Helps Avoid
The most common Flexbox mistake is confusing which axis justify-content and align-items actually control once flex-direction is set to column, both properties keep the same name but swap which physical direction they affect. The second: setting align-content and expecting it to do something when flex-wrap is nowrap, align-content only has a visible effect when there are multiple wrapped lines to distribute, with a single line (the default, no-wrap behavior) it's a no-op, this tool only emits align-content in the output when wrap is actually enabled, to avoid generating a CSS declaration with no visible effect. The third, an accessibility-relevant one: the order property changes visual order only, not DOM order or tab order, reordering interactive elements with order can create a mismatch between visual reading order and keyboard navigation order that's easy to overlook.