Flexbox Generator: Free Visual CSS Builder

This flexbox generator lets you build a CSS flexbox layout visually: pick direction, wrap, alignment and gap, watch numbered boxes rearrange in a live preview, and copy the finished container CSS. It suits beginners learning flexbox and developers who want a quick starting point for navbars, card rows and centered content.

What Is Flexbox in CSS?

Flexbox, formally the CSS Flexible Box Layout Module, is a layout model that arranges child elements in a single row or a single column and controls how they share space. You turn it on by setting display: flex on a parent element. Its direct children then become flex items.

Everything in flexbox revolves around two axes. The main axis runs in the direction set by flex-direction (horizontal for row, vertical for column). The cross axis runs perpendicular to it. The justify-content property aligns items along the main axis, and align-items aligns them along the cross axis. Change the direction and the two properties swap roles, which is the part most beginners find confusing.

Flexbox handles one dimension at a time. When you need rows and columns together, such as a page grid with cells aligned in both directions, CSS Grid is the better fit. Many layouts use both: Grid for the page frame and flexbox for the components inside it.

How to Use the Flexbox Generator

You build a layout by changing dropdowns and sliders, and the preview updates on every change. Follow these steps:

1. Choose a flex-direction: row, row-reverse, column or column-reverse. Row lays boxes out left to right, column stacks them top to bottom.
2. Set flex-wrap to nowrap, wrap or wrap-reverse. Use wrap when boxes should drop to a new line instead of squeezing together.
3. Pick justify-content (flex-start, flex-end, center, space-between, space-around or space-evenly) to position boxes along the main axis.
4. Pick align-items (stretch, flex-start, flex-end, center or baseline) to position boxes along the cross axis.
5. Choose align-content if your boxes wrap onto several lines. It controls how those lines are spaced inside the container.
6. Drag the gap slider (0 to 40 px), the Number of Items slider (1 to 12) and the Container Height slider (80 to 300 px) until the preview matches what you have in mind.
7. Read the Generated CSS box and press Copy to paste the rules into your stylesheet.

Worked Example: A Navigation Bar Layout

Say you want a header where a logo sits on the far left, links sit on the far right and everything is vertically centered. Set flex-direction to row, flex-wrap to nowrap, justify-content to space-between, align-items to center and gap to 16. Leave Number of Items at 4 so you can see four boxes spread across the bar.

The Generated CSS box then shows a .container rule with display: flex, flex-direction: row, flex-wrap: nowrap, justify-content: space-between, align-items: center, align-content: normal and gap: 16px. In the preview, box 1 touches the left edge, box 4 touches the right edge, and boxes 2 and 3 sit evenly between them with at least 16 px of space around each.

To read this result: space-between puts the first and last items against the container edges and splits the leftover space between the rest. If you wanted equal space at the edges too, switch to space-evenly and compare the preview. Then rename .container to your real class, such as .site-header, and apply it to the parent element.

How Do You Read and Act on the Results?

The preview shows exactly what each property does, and the CSS box gives you the matching declarations. This table summarizes the controls and when each one is the right choice.

When align-content seems to do nothing

Align-content only works when there is more than one line of items. With nowrap, all boxes stay on one line, so changing it has no visible effect. Switch flex-wrap to wrap, raise Number of Items to 10 or 12, and shrink the layout until the boxes break onto a second row. Now the option shows its effect.

When align-items looks wrong

Stretch, the default, makes items as tall as the container (in a row) unless they have their own height. If your boxes look oddly tall, choose flex-start or center. Baseline lines up the text baselines of items, which helps when items have different font sizes.

How Do You Make Flexbox Fill Width, Fill Height, Go Vertical or Wrap?

Most common flexbox questions are answered by one property or one item-level rule. Use these quick fixes after you copy the container CSS.

• Vertical layout: set flex-direction to column. Justify-content now works top to bottom, and align-items works left to right.
• Horizontal layout: keep flex-direction on row, the default.
• Fill the full width: a flex container is a block-level box, so it already spans the width of its parent. To make the items themselves stretch across it, add flex: 1 to each child in your own CSS so they share the space equally.
• Fill the height: give the container a height (or let a parent supply one) and keep align-items on stretch. In a column, add flex: 1 to the item that should grow.
• Wrap: set flex-wrap to wrap and give items a width or a minimum width, so the browser knows when to start a new line.
• Responsive behavior: wrap plus item widths gets you far. Add a media query to switch flex-direction from row to column on narrow screens.

Who Is This Flexbox Generator For?

It helps anyone who wants to see flexbox rules in action before committing them to code. Typical situations include:

• Students who are learning what justify-content and align-items do and want to test every option in seconds.
• Front-end developers who need a quick starting rule for a navbar, toolbar, footer or pricing-card row.
• Designers handing off a layout who want to describe spacing and alignment in real CSS.
• Developers debugging a layout who want to rebuild it in isolation and spot which property is causing the problem.

Once the layout is set, polish the pieces inside it with the border radius generator for rounded cards and the CSS box shadow generator for depth.

Best Practices and Troubleshooting Tips

A few habits prevent most flexbox surprises. Build with the preview first, then test the copied CSS in your real page, because your content will differ from the numbered boxes.

• Use gap instead of margins. Gap adds space only between items, so you avoid extra space on the first or last item. It is supported in current major browsers.
• Set a container height before centering vertically. Align-items: center only centers within the space available. If the real container is as tall as its content, there is nothing to center against.
• Check items that overflow. With nowrap, items shrink to fit, and long content can still overflow. Try wrap, or set a minimum width on the items.
• Remember reversed directions. Row-reverse and column-reverse change the visual order only. Screen readers and keyboard focus still follow the HTML order, so use them with care.
• Keep text readable. If you place text on colored boxes, run the pair through the color contrast checker.
• Tidy before committing. Paste the rule into your file and run the surrounding stylesheet through the code beautifier if the indentation does not match.

What Are the Limits of This Tool?

The generator writes the container rule only. It does not output item-level properties such as flex-grow, flex-shrink, flex-basis, order or align-self, and it does not create the HTML for your items. You add those in your own code when a single child needs special treatment.

The Container Height slider sizes the preview so you can judge vertical alignment. The copied CSS does not include a height declaration, so set one yourself on the real container when your layout needs it. The preview boxes are numbered placeholders with a minimum size of 40 px, so real content with different sizes will space out differently. Treat the result as an accurate starting point and adjust once your actual content is in place.

Open the generator above, set your direction, wrap and alignment, and copy the CSS when the preview looks right. For more helpers like it, browse the web developer tools collection.