Flexbox Generator Online

How to Build a Flexbox Layout Online

1. Set the Parent Container: Toggle display: flex (or inline-flex if the container itself should sit inline with surrounding text). Pick a flex-direction — row (default, items flow left-to-right on the main axis), row-reverse, column, or column-reverse — and choose flex-wrap: nowrap (squeeze onto one line), wrap (overflow onto new lines), or wrap-reverse.
2. Align on Both Axes: Pick justify-content to distribute items along the main axis — flex-start, flex-end, center, space-between, space-around, or space-evenly. Pick align-items for the cross axis — stretch (default), flex-start, flex-end, center, or baseline. Set gap (e.g. 16px, 1rem) to space items without margin hacks.
3. Add Child Items and Per-Item Overrides (Optional): Choose how many child boxes to preview, then set per-item order (negative numbers move items earlier), flex-grow, flex-shrink, flex-basis — or the shorthand flex (1, auto, none). Use align-self to override the container's align-items for a single item.
4. Copy the CSS: The live preview updates as you tweak controls. Copy the generated .container { ... } and .item { ... } rules straight into your stylesheet. Nothing is uploaded — everything runs in your browser session.

Why Use a Flexbox Generator?

Flexbox (CSS Flexible Box Layout) is the one-dimensional layout system every modern site uses for navbars, button rows, card lists, form fields, and centered hero blocks. The spec has ~96% global browser support, but the property combinations — justify-content vs align-items, flex-wrap interactions, the three-value flex shorthand — are easy to mis-remember. Building visually beats trial-and-error in DevTools:

• Center anything in three lines — display: flex; justify-content: center; align-items: center; perfectly centers a child both axes, replacing the old position: absolute; transform: translate(-50%, -50%) hack.
• Responsive direction switch — start with flex-direction: column for mobile, then flip to row inside a @media (min-width: 768px) block. The generator lets you preview both states without DOM reflows.
• Card grids with even gaps — flex-wrap: wrap plus gap: 16px replaces the negative-margin trick on .row / .col wrappers that dominated pre-2021 CSS frameworks.
• Navbar with logo on left, links on right — justify-content: space-between on the nav container; no floats, no clearfix.
• Holy-grail layout — header, footer, sidebar, main content area. flex: 1 on <main> makes it absorb leftover space while the sidebar stays its natural width.
• Form field alignment — labels and inputs on the same baseline with align-items: baseline, regardless of font-size differences.

Once your stylesheet is ready, clean it up with the CSS Formatter during development, then run it through the CSS Minifier before shipping to production.

flex-direction — Which Axis is "Main"?

The main axis is whichever direction items flow; the cross axis is perpendicular. This is the single most-confused part of flexbox: justify-content always works on the main axis, align-items always works on the cross axis — so which property does what flips when you change flex-direction.

flex-direction	Main axis	Cross axis	justify-content controls	align-items controls
row (default)	Left → right	Top → bottom	Horizontal spacing	Vertical alignment
row-reverse	Right → left	Top → bottom	Horizontal spacing (mirrored)	Vertical alignment
column	Top → bottom	Left → right	Vertical spacing	Horizontal alignment
column-reverse	Bottom → top	Left → right	Vertical spacing (mirrored)	Horizontal alignment

flex Shorthand — 1 1 0 vs auto vs none

flex is the shorthand for flex-grow flex-shrink flex-basis. The three keyword shortcuts cover 90% of real use cases — knowing the difference saves a lot of debugging.

Shorthand	Expands to	Behavior	When to use
flex: 1	1 1 0%	Item grows to fill space, shrinks if needed, starts at 0 width — siblings with the same value end up equal width	Equal-width columns ignoring content size
flex: auto	1 1 auto	Grows and shrinks, but starts at the item's natural content width — larger content gets more space	Content-aware sizing (nav with mixed-length links)
flex: none	0 0 auto	Never grows, never shrinks, sticks to natural size	Fixed sidebars, logos, icon buttons
flex: 0 1 auto	(the default)	Doesn't grow, shrinks if needed, natural size	Default item — same as setting nothing
flex: 2	2 1 0%	Takes 2× the space of a sibling with flex: 1	Weighted column widths (e.g., main 2fr, sidebar 1fr in grid-speak)

Frequently Asked Questions

What's the difference between flex-grow, flex-shrink, and flex-basis?

flex-basis is the item's starting size along the main axis — before any growing or shrinking happens. flex-grow is how greedily an item claims leftover space (0 = stay at basis, 1+ = grow proportionally to siblings). flex-shrink is how willingly an item gives up space when the container is too small (default 1 = shrinks, 0 = never shrinks below basis). The three together let you say "this item should start at 200px, grow to fill available space, and refuse to shrink below 200px" via flex: 1 0 200px.

When should I use Grid instead of Flexbox?

Flexbox is one-dimensional — a single row OR a single column. Grid is two-dimensional — rows AND columns at once. If you're laying out a nav bar, a list of buttons, or aligning items inside a card, use flexbox. If you're laying out a full page (header / sidebar / main / footer) or a card grid where rows and columns must align across both axes, use Grid. They compose well: Grid for the page macro-layout, flexbox for micro-layouts inside each grid cell.

Why does justify-content: space-between leave a huge gap on the last row?

Because flexbox treats each wrapped row independently. space-between pins the first item to the start edge and the last item to the end edge, then evenly distributes the rest. When the last row has fewer items than earlier rows, those few items still get pushed to the start and end — leaving enormous gaps in the middle. Fixes: switch to space-evenly or space-around (one-item rows center), use gap plus justify-content: flex-start and let items align naturally, or add invisible flex items as fillers. For genuine grid behavior with consistent gaps on every row, use CSS Grid instead.

When can I actually use gap on a flexbox container?

Gap on flexbox is broadly safe now (~95% global support per caniuse). Chrome and Edge shipped it in version 84 (July 2020), Firefox in 63 (October 2018), and Safari 14.1 on macOS Big Sur (April 26, 2021) — iOS Safari 14.5 followed in late April 2021. Anything older than that silently ignored gap on flex containers (it worked in CSS Grid earlier). For an audience that includes pre-2021 iOS users, fall back to margin on items with a negative margin on the parent.

What's the difference between align-items and align-content?

align-items aligns items on the cross axis within a single line — it's what you want 99% of the time. align-content only does anything when flex-wrap: wrap is producing multiple lines, and it controls how those lines are spaced relative to each other on the cross axis (same value vocabulary as justify-content: flex-start, center, space-between, etc.). On a single-line flex container, align-content is a no-op.

How do I build the "holy grail" layout (header, footer, sidebar, main) with flexbox?

Set the page wrapper to display: flex; flex-direction: column; min-height: 100vh. Inside, the header and footer stay their natural height; the middle section gets flex: 1 so it grows to absorb leftover viewport height. Inside that middle section, set display: flex; flex-direction: row and give the main content flex: 1 while the sidebar stays a fixed width (e.g., flex: 0 0 240px). This is the canonical flexbox layout and works everywhere flexbox does.

How do I switch flex-direction between mobile and desktop?

Use a media query. Default to flex-direction: column on the container so items stack vertically on phones. Then inside @media (min-width: 768px) { .container { flex-direction: row; } }, flip to row for tablets and up. This is the cleanest mobile-first responsive pattern — no display: block toggle needed, no JavaScript, items keep their flex sizing in both layouts. The generator lets you preview both states by toggling direction without writing the media query.

Is flexbox safe to use without fallbacks in 2026?

Yes. caniuse reports ~96% global support; every evergreen browser has full flexbox since Chrome 21 (2012), Safari 6.1 (2012), Firefox 28 (2014), and Edge 12 (2015). The only partial-support browsers in the wild are IE 10–11 (which Microsoft retired in June 2022) and ancient Android Browser builds. If your target audience excludes IE, ship flexbox bare. The gap property is the only sub-feature with a more recent cutoff (Safari 14.1, April 2021).

Does the order property change the actual DOM order?

No — it only changes visual order. The HTML source order stays the same, which means screen readers, tab order, and Tab-key focus traversal all follow the original DOM. Use order for layout tweaks (push a sale badge before the product title visually) but never for content reordering that affects meaning — that's an accessibility bug. WCAG recommends keeping DOM order matching reading order.