CSS Flexbox Generator
Flexbox takes the pain out of CSS layout alignment, but trying to remember the difference between `justify-content` and `align-items` can be frustrating. The CSS Flexbox Generator provides a fully interactive sandbox. Add UI blocks directly onto the canvas, tweak the flex parent properties, see the real-time layout changes, and instantly export the perfectly formatted CSS.
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This tool runs completely inside your browser using client-side WebAssembly and JS. Zero data is ever sent to our servers.
Flexbox Properties
How to use this tool
- Use the 'Items' slider in the top left of the preview to add or remove blocks from your flex container.
- Change `flex-direction` to switch between a horizontal Row layout (default) or a vertical Column layout.
- Adjust `justify-content` to position your items along the main axis (e.g., center them, or space them evenly).
- Adjust `align-items` to position your items along the cross axis (e.g., stretch them to fill the height).
- Use the `gap` slider to implement modern, clean spacing between your items without messy margins.
Example Usage
Perfect Div Centering
.flex-container {
display: flex;
justify-content: center;
align-items: center;
}Standard Navigation Bar Spacing
.flex-container {
display: flex;
justify-content: space-between;
align-items: center;
}When to use this tool
- Centering a child element vertically and horizontally within a parent div (the classic CSS problem).
- Building responsive Top Navigation bars where the logo is on the far left and links are on the far right.
- Creating fluid grids of cards that wrap cleanly to the next row on mobile devices using `flex-wrap: wrap`.
- Rapidly prototyping UI layouts visually before writing the raw CSS code.
Frequently Asked Questions
What is the difference between justify-content and align-items?
`justify-content` aligns items along the MAIN axis, while `align-items` aligns them along the CROSS axis. If your `flex-direction` is `row` (horizontal), `justify-content` controls left-to-right alignment, and `align-items` controls top-to-bottom alignment. If you switch to `column`, these axes swap!
Why should I use gap instead of margin?
The `gap` property (formerly `grid-gap`) is modern flexbox's best feature. Unlike margins on individual items, `gap` only applies spacing *between* items. You don't have to write messy selectors like `:last-child { margin-right: 0; }` anymore.
What does align-content do?
`align-content` only works when you have multiple rows of items (which requires `flex-wrap: wrap`). It controls how the multiple rows space themselves out vertically within the parent container, similar to how `justify-content` spaces out individual items.
Are flexbox layouts responsive?
Inherently, yes! Flex items are designed to grow, shrink, and wrap to accommodate available space. Using `flex-wrap: wrap` is one of the easiest ways to ensure a row of items cleanly stacks into a column on mobile devices.