Flexbox is the layout mode most developers reach for first, yet remembering which property goes on the container and which on the items, and how justify-content differs from align-items, still trips people up. This generator lets you build a flex container visually: choose the direction, the main-axis and cross-axis alignment, and the gap, and watch a live preview rearrange itself as you change each control. Below the preview it prints the exact CSS for the container, ready to copy into your stylesheet. Seeing the effect of each property immediately, rather than editing code and refreshing, is the fastest way to build an intuition for flexbox, and the generated code is clean enough to use in production without tidying up afterwards.
Quick Answer: Pick flex direction, alignment, and gap, watch the live preview, and copy the container CSS.
Free Online Tool
CSS Flexbox Generator
Flexbox you can see: change a control, watch the layout move.
How to Use the CSS Flexbox Generator
- Choose a flex direction: row, row-reverse, column, or column-reverse.
- Set justify-content for alignment along the main axis.
- Set align-items for alignment along the cross axis.
- Adjust the gap between items to taste.
- Copy the generated CSS and paste it into your stylesheet.
Key Features
- Live preview that rearranges instantly as you change controls.
- All four flex directions including the reversed variants.
- Main-axis and cross-axis alignment controls side by side.
- Gap control for consistent spacing without margins.
- Copy-ready container CSS with nothing extra to clean up.
Best Practices and Tips
- Justify-content works along the main axis, which is horizontal in a row and vertical in a column; that swap confuses almost everyone at first.
- Align-items controls the cross axis, so in a row it moves items up and down, not left and right.
- Use gap instead of margins between items; it applies only between items, never at the container edges.
- Wrap matters: without flex-wrap, items shrink rather than dropping to a new line when space runs out.
- A single item can break the rules with align-self, which overrides align-items for that item alone.
Common Mistakes to Avoid
- Setting justify-content and align-items on the flex items instead of the container, where they do nothing.
- Expecting gap to add space around the outside of the layout; it only separates items from each other.
- Forgetting that column direction flips which axis is main and which is cross.
- Using fixed widths on items and then wondering why flex shrinking distorts them.
Frequently Asked Questions
What is the difference between justify-content and align-items?
Justify-content aligns items along the main axis, the direction items flow in, while align-items aligns them along the cross axis, perpendicular to that flow. In a row, justify-content moves items horizontally and align-items moves them vertically; in a column, the two swap roles.
Do I need flex-wrap?
Only if you want items to drop onto new lines when they run out of space. Without it, flex items shrink to fit a single line, which is fine for toolbars but terrible for card grids. Add flex-wrap: wrap to the generated container CSS whenever the layout should reflow.
Why do my items not stretch to fill the container?
By default align-items is stretch, so items do fill the cross axis, but only if they have no fixed size on that axis. A fixed height on items in a row, or a fixed width in a column, overrides stretching, so remove the fixed size if stretching is what you want.
Can I use the generated CSS in production?
Yes. The output is plain, standard flexbox CSS with no framework dependency and no vendor prefixes needed in modern browsers. Paste it into your stylesheet, add your own item styles, and it works as shown in the preview.
What is the gap property?
Gap sets the space between flex items, replacing the old trick of margins on every item except the last. It is cleaner because it never adds space at the container edges, and it works in both directions when items wrap onto multiple lines.