WebToolsPlanet
css Tools

Flexbox Generator

Build CSS Flexbox layouts visually — configure every container and item property and get ready-to-use CSS.

Last updated: March 25, 2026

Client-Side Processing
Input Data Stays on Device
Instant Local Execution

Find this tool useful? Support the project to keep it free!

Buy me a coffee

What is Flexbox Generator?

CSS Flexbox (Flexible Box Layout) is the most widely used layout model for component-level responsive design. It excels at distributing space along a single axis — either horizontally (row) or vertically (column) — and provides powerful alignment capabilities for all elements within a container. Flexbox is the foundation of virtually every modern navigation bar, button group, card layout, and centering technique used in production web applications.

Despite being one of the most searched CSS topics on the web, Flexbox has a notoriously steep initial learning curve due to the interaction between container properties (flex-direction, justify-content, align-items, flex-wrap) and item properties (flex-grow, flex-shrink, flex-basis, align-self, order). This visual generator lets you interact with every Flexbox property live, instantly seeing how changes to the container affect children — making it the fastest way to learn and use Flexbox correctly.

How to Use Flexbox Generator

1

Set the container's flex-direction (row, row-reverse, column, column-reverse) using the buttons

2

Choose how items are distributed on the main axis using justify-content (flex-start, center, space-between, etc.)

3

Set cross-axis alignment with align-items (stretch, center, flex-start, flex-end, baseline)

4

Toggle flex-wrap if items should wrap to the next line when they overflow the container

5

Click any individual child item to configure its flex-grow, flex-shrink, flex-basis, or align-self overrides

6

Copy the generated .container CSS and .item CSS to use in your project

Common Use Cases

  • Building a horizontal navigation bar with links evenly distributed using space-between
  • Perfectly centering a modal or card both vertically and horizontally inside a full-height container
  • Creating an equal-height card row where cards grow to fill the available width
  • Building a sticky sidebar layout where the main content area stretches to fill remaining space
  • Arranging a toolbar of icon buttons with consistent spacing using gap instead of margins
  • Creating a responsive form layout where labels and inputs align naturally on the same row
  • Building a flex-based footer with 3 columns: left-aligned brand, centered links, right-aligned social icons
  • Learning why flex-basis 0 vs auto changes how flex-grow distributes space differently

Example Input and Output

A centered hero section with a column-direction flex container:

Flexbox Configuration
Container Settings:
  flex-direction: column
  justify-content: center
  align-items: center
  gap: 24px
  min-height: 100vh

Item (Button) Settings:
  flex-grow: 0
  flex-shrink: 1
  flex-basis: auto
Generated CSS
.flex-container {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 24px;
  min-height: 100vh;
}

.flex-item {
  flex: 0 1 auto; /* shorthand: grow shrink basis */
}

Client-Side Processing

The Flexbox preview and CSS generation runs entirely in your browser. No layout data is sent to our servers.

Perfect Centering — Finally

The simplest way to center any element both horizontally and vertically in a container: give the parent display: flex; justify-content: center; align-items: center. Add min-height: 100vh if centering in the viewport. This single pattern replaces all legacy centering hacks.

Flex vs Grid Decision

Use Flexbox for: navigation bars, toolbars, button groups, centering, one-directional item distribution. Use Grid for: page-level layouts, multi-column card grids, any layout where you need both row AND column control simultaneously. They are complementary — Grid for the outer shell, Flexbox for component internals.

Frequently Asked Questions

What is the difference between justify-content and align-items?
justify-content aligns items along the main axis (left-right in row direction, top-bottom in column direction). align-items aligns items along the cross axis (perpendicular to main). In a row direction flex container, justify-content controls horizontal distribution and align-items controls vertical alignment. Both flip if you change flex-direction to column.
What does flex: 1 mean?
flex: 1 is shorthand for flex-grow: 1, flex-shrink: 1, flex-basis: 0%. It tells an item to grow and shrink equally relative to other flex items, and to start calculating its size from 0 rather than from its content size. flex: 1 on all siblings makes them share space equally. Use flex: 1 on just one sibling to make it fill all remaining space while others stay sized to their content.
When should I use margin: auto vs justify-content for spacing?
margin: auto on a flex item absorbs all available space on that side, enabling "push" patterns: set margin-left: auto on the last nav item to push it to the far right while other items huddle left. justify-content distributes space uniformly across ALL items. For "one item far right, rest at left" patterns, margin: auto is the correct tool.
What is align-content vs align-items?
align-items aligns items WITHIN a single row. align-content aligns the rows themselves within the container — only applies when there are multiple rows due to flex-wrap. If you have only one row, align-content has no effect. If you have wrapped rows and want to control their spacing within the container, use align-content.
What is flex-basis and how does it differ from width/height?
flex-basis sets the initial size of a flex item before flex-grow or flex-shrink adjusts it. It overrides width (in row direction) or height (in column direction). Set flex-basis: 300px to suggest the item starts at 300px before the flexbox algorithm runs. Setting flex-basis: auto uses the item's content size as the starting point. flex-basis: 0 forces all items to start at 0 so flex-grow distributes space completely proportionally.
How do I make a flexbox layout responsive without media queries?
Use flex-wrap: wrap combined with a flex-basis that sets a minimum column width. Example: .item { flex: 1 1 250px; } means each item can grow, can shrink, and starts at 250px. When the container is wide enough, items sit side by side; when it's too narrow, they automatically wrap to the next line. Combine with gap for gutter spacing.

How This Tool Works

The flex container preview is a live div rendered using the currently selected CSS properties. React state tracks each container property (flex-direction, justify-content, etc.) and each selected item's properties. On every change, both the visual preview and the CSS output code block are re-generated by serializing the active property values into a formatted CSS string. Only non-default values are output to reduce noise in the generated CSS.

Technical Stack

Browser-native CSS FlexboxReact state-driven previewCSS property serializerClient-side only

Related Tools

CSS Unit Converter
Convert between PX, REM, EM, VW, VH, and % CSS units — with configurable base font size and live conversion.
Box Shadow Generator
Create CSS box shadows with a visual editor.
CSS Gradient Generator
Create beautiful CSS gradients with a visual editor.
Border Radius Generator
Create complex CSS border-radius shapes with independent corner controls — from rounded buttons to organic blobs.
CSS Grid Generator
Build CSS Grid layouts visually — configure columns, rows, gaps, and named areas and copy production-ready CSS.
CSS Minifier
Compress and minify CSS code to reduce file size and speed up page loads.