CSS Flexbox Generator
Configure flex direction, wrapping, and alignment options visually. Get production-ready CSS instantly. All in your browser.
Quick Presets
Container
flex-direction
flex-wrap
Items
Live Preview
Generated CSS
.flex-container {
display: flex;
flex-direction: row;
flex-wrap: nowrap;
justify-content: flex-start;
align-items: stretch;
gap: 16px;
}
.flex-item {
flex: 0 1 auto;
background: rgba(108, 92, 247, 0.15);
border: 1px solid rgba(108, 92, 247, 0.3);
border-radius: 8px;
padding: 1rem;
}CSS Flexbox: Axes, Alignment & Common Layout Recipes
1. Main Axis vs Cross Axis
Every flex property revolves around two axes defined by flex-direction: the main axis (the direction items flow — horizontal for row, vertical for column) and the cross axis (perpendicular to it). justify-content always aligns along the main axis; align-items and align-content always align along the cross axis. This is why swapping from row to column flips what "horizontal" and "vertical" mean for these properties — the generator's live labels update to reflect this as you change direction.
2. How to Use This Generator
Start from a preset (Nav Bar, Card Row, Centered Stack, Sidebar + Main) or configure from scratch: set direction, wrap behavior, justify-content, align-items, and gap for the container, then set the flex shorthand for individual items. The live preview updates instantly with numbered placeholder boxes so you can see exactly how items will flow and align. Copy the generated CSS — it includes both the .flex-container and a sample .flex-item ruleset — and adapt the class names to your actual markup.
3. Common Layout Recipes
A nav bar uses row direction with justify-content: space-between to push logo and menu links to opposite ends, and align-items: center to vertically center everything. A centered stack (a common way to vertically and horizontally center content) uses column direction with both justify-content: center and align-items: center. A sidebar + main content layout gives the sidebar a fixed-width flex-basis (0 0 240px) and the main content flex: 1 so it fills the remaining space.
4. Common Mistakes
A frequent mistake is forgetting flex-wrap: wrap on a row of items that needs to reflow on smaller screens — without it, flex items shrink down to their minimum content size rather than wrapping to a new line, which can cause overflow or squished content. Another is confusing align-items (which aligns items within a single line) with align-content (which controls spacing between multiple wrapped lines) — align-content only has a visible effect when flex-wrap is active and there's extra cross-axis space to distribute.
5. Limitations
This generator produces a uniform flex value applied to every item in the preview — real layouts often need different flex values per item (a fixed-width sidebar next to a flexible main area, for example), which you'll need to set manually per element after copying the base CSS. It also doesn't cover nested flex containers or the interaction between Flexbox and CSS Grid when combining both layout systems on the same page.
Frequently Asked Questions
What is CSS Flexbox?
CSS Flexbox (Flexible Box Layout) is a one-dimensional layout model that efficiently distributes space along a single axis — either a row or a column. It's ideal for navigation bars, card rows, form controls, and centering content.
What does justify-content vs align-items do?
justify-content controls alignment along the main axis (the direction set by flex-direction). align-items controls alignment along the cross axis (perpendicular to flex-direction). For a row layout: justify-content = horizontal, align-items = vertical.
What is flex-wrap?
By default, flex items try to fit onto one line. Setting flex-wrap: wrap allows items to flow onto multiple lines when they run out of space, instead of shrinking below their minimum size.
When should I use Flexbox instead of CSS Grid?
Use Flexbox for one-dimensional layouts: a row of navigation links, a line of buttons, a vertical stack of cards. Use CSS Grid when you need two-dimensional control — defining both rows and columns simultaneously.
What does the flex shorthand property actually control?
flex is shorthand for three values: flex-grow (how much an item expands to fill extra space, relative to siblings), flex-shrink (how much it shrinks when space is tight), and flex-basis (its starting size before growing/shrinking). "1 1 auto" means grow and shrink freely from its natural size; "0 0 200px" means a fixed 200px width that never grows or shrinks — useful for a sidebar that shouldn't resize.
Does Flexbox have full browser support?
Yes. Flexbox has been supported without vendor prefixes in all major browsers since around 2017 (Chrome, Firefox, Safari, Edge). There is no meaningful compatibility reason to avoid it in a modern project.