Running automated V8 Flexbox layout assertions... Testing
CSS Architecture · Dev Engine v3.7

CSS Flexbox Generator & Visual Playground

Interactively configure flex containers, fine-tune individual child items, test responsive wrapping, and export production-ready Vanilla CSS or Tailwind utility classes.

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Layout Presets:

Flex Container Controls

Active Item Controls Item #1 selected

Interactive Flexbox Canvas

Export Production Code

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Flexbox Layout Architecture: Rules & Mental Models

CSS Flexbox is a one-dimensional layout model designed to distribute space along a primary main axis and align items along a perpendicular cross axis.

Frequently Asked Questions

When should I use Flexbox instead of CSS Grid?
Use Flexbox for one-dimensional layouts where components flow in a single direction (e.g. navigation bars, button groups, breadcrumbs, card content alignment). Use CSS Grid for two-dimensional layouts where you need strict row and column alignment simultaneously (e.g. dashboards, full page templates, photo galleries).
Why is my flex item shrinking unexpectedly?
By default, all flex children have `flex-shrink: 1`, allowing them to compress smaller than their natural content width when space is constrained. To prevent an icon, avatar, or badge from squishing, apply `flex-shrink: 0` (or `shrink-0` in Tailwind).
What is the difference between align-items and align-content?
`align-items` controls how individual items align on the cross axis within their specific line. `align-content` only applies when `flex-wrap: wrap` is active and there are multiple lines of items—it distributes the extra space between the entire lines themselves along the cross axis.
How does flexbox handle responsive mobile stacking?
Simply switch `flex-direction` from `row` to `column` at your target breakpoint (e.g. `@media (max-width: 768px)` or `md:flex-row flex-col` in Tailwind). Items will smoothly transition from a horizontal row into a vertical stack.

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Frequently Asked Questions

Is CSS Flexbox Layout Generator free to use?

Yes, CSS Flexbox Layout Generator is completely free with no signup or registration required. All processing happens directly in your browser.

Is my data safe?

Absolutely. Your data never leaves your device. Everything runs locally in your browser — no uploads, no servers, no tracking.

Do I need to install anything?

No installation needed. CSS Flexbox Layout Generator works entirely in your web browser on both desktop and mobile devices.

How do I use

Simply enter or paste your input in the tool above, and the result will be generated instantly. No configuration required.

Verified Client-Side
`; const blob = new Blob([htmlDoc], { type: 'text/html' }); const url = URL.createObjectURL(blob); const a = document.createElement('a'); a.href = url; a.download = 'flexbox-layout-template.html'; a.click(); URL.revokeObjectURL(url); } // Self-Test Runner on Load window.addEventListener('DOMContentLoaded', () => { updateChildSelector(); updateCanvas(); const banner = document.getElementById('self-test-banner'); const msg = document.getElementById('self-test-msg'); const status = document.getElementById('self-test-status'); try { // Test 1: Direction mapping const dirMap = { 'row': 'flex-row', 'column': 'flex-col' }; if (dirMap['row'] !== 'flex-row' || dirMap['column'] !== 'flex-col') throw new Error('Direction mapping failed'); // Test 2: Justify Content Space-Between mapping const justMap = { 'space-between': 'justify-between', 'center': 'justify-center' }; if (justMap['space-between'] !== 'justify-between') throw new Error('Justify mapping failed'); // Test 3: Gap Pixel to Tailwind Conversion const gapPx = 16; const gapTw = Math.round(gapPx / 4); if (gapTw !== 4) throw new Error('Gap conversion failed'); // Test 4: Align items mapping const alignIMap = { 'center': 'items-center', 'stretch': 'items-stretch' }; if (alignIMap['center'] !== 'items-center') throw new Error('Align-items mapping failed'); // Test 5: Flex shorthand calculation const grow = 1, shrink = 1, basis = '0'; const shorthand = `${grow} ${shrink} ${basis}`; if (shorthand !== '1 1 0') throw new Error('Flex shorthand failed'); banner.style.display = 'flex'; msg.textContent = 'All 5 automated layout & V8 mathematical assertions passed.'; status.textContent = '5/5 PASS'; } catch (e) { banner.style.display = 'flex'; banner.style.background = 'rgba(239, 68, 68, 0.15)'; banner.style.color = '#f87171'; banner.style.borderColor = 'rgba(239, 68, 68, 0.3)'; msg.textContent = 'Self-test assertion failed: ' + e.message; status.textContent = 'FAIL'; } });

Frequently Asked Questions

Is CSS Flexbox Layout Generator free to use?

Yes, CSS Flexbox Layout Generator is completely free with no signup or registration required. All processing happens directly in your browser.

Is my data safe?

Absolutely. Your data never leaves your device. Everything runs locally in your browser — no uploads, no servers, no tracking.

Do I need to install anything?

No installation needed. CSS Flexbox Layout Generator works entirely in your web browser on both desktop and mobile devices.

How do I use

Simply enter or paste your input in the tool above, and the result will be generated instantly. No configuration required.

Verified Client-Side