How to Create Rounded Corners and Blob Shapes in CSS

To create rounded corners in CSS, use the border-radius property and adjust each corner with a visual generator that shows a live preview and outputs copy-ready code. Instead of guessing pixel values and refreshing the browser, you drag a slider per corner, watch a preview box round in real time, and copy the finished declaration in one click.

Getting corner radii right by hand is tedious. A card needs a subtle 8px curve, a pill button needs a huge one, and a modern hero blob needs four different asymmetric values. Typing numbers and reloading wastes minutes each time. A visual editor collapses that loop to seconds.

Why use a visual border-radius editor?

The border-radius shorthand is more capable than most developers use it for. It can round all four corners equally, round each one independently, and even accept separate horizontal and vertical radii per corner to produce fluid, egg-like shapes. Remembering that syntax from memory is error-prone. A generator handles the notation for you, so you focus on how the shape looks rather than which value belongs where.

This tool is built for front-end developers, UI designers, and anyone assembling a component library who wants consistent, intentional corners. It is equally handy for learners who want to see how the property behaves as they experiment.

How to generate border-radius CSS in your browser

1. Drag the slider for any single corner to round it on its own, or switch on Link corners to move all four together for a uniform curve.
2. Watch the preview box reshape live as you adjust each value, so you can dial in the exact look before committing.
3. Turn on the 8-value syntax when you want an organic blob, then shape the vertical radii separately from the horizontal ones.
4. Click Copy CSS to grab the full border-radius declaration and paste it straight into your stylesheet.

Standard corners vs. the 8-value blob syntax

The single biggest thing this tool unlocks is the slash syntax, which is what turns a plain rounded box into a modern blob. Here is how the two approaches compare:

Approach	Example value	Best for
Single value	border-radius: 12px	Cards, buttons, inputs with even corners
Four values	border-radius: 10px 20px 30px 40px	Chat bubbles, tabs, asymmetric callouts
50% on a square	border-radius: 50%	Circles and avatar frames
8-value slash	border-radius: 30% 70% 70% 30% / 30% 30% 70% 70%	Organic blobs in hero sections and decorative backgrounds

Reach for pixels when you want a fixed corner size regardless of how big the element gets, such as a button that should always have the same rounding. Reach for percentages when the shape should scale with the element, which is exactly what circles, avatars, and blobs need. This generator works in percentages so your shapes stay proportional at any size.

Key features and benefits

• Per-corner sliders with an instant live preview.
• A link toggle to edit all four corners at once for uniform rounding.
• The 8-value slash syntax for asymmetric, organic blob shapes.
• Clean, copy-ready CSS output with no clutter.
• Percentage-based radii that scale with the element.
• Completely free and fully client-side, so it works offline once loaded.

Try the CSS Border Radius Generator now — it's free and runs entirely in your browser.

Frequently asked questions

What order do the four border-radius values follow?

They run clockwise starting from the top-left corner: top-left, top-right, bottom-right, then bottom-left. So border-radius: 10px 20px 30px 40px rounds the top-left by 10px and the bottom-left by 40px. The generator keeps this order correct automatically.

How do I make a perfect circle with border-radius?

Give a square element border-radius: 50%. Each corner's radius becomes half the width and height, which merges them into a smooth circle. On a rectangle, 50% produces an ellipse instead, which is why avatars are usually square before rounding.

What is the 8-value slash syntax?

It lets you set a horizontal and a vertical radius for every corner, separated by a slash. The four values before the slash control horizontal radii and the four after control vertical radii, and mismatching them is precisely how designers build the asymmetric blob shapes popular in modern layouts.

Why does a very large radius stop changing the shape?

Browsers cap each radius so neighbouring corners never overlap. Once the combined radii exceed the element's side length, the values are scaled down proportionally, so pushing a slider past that point has no further visible effect.

Should I use pixels or percentages?

Use pixels for consistent corners on fixed components like buttons and cards, and percentages when the rounding should track the element's size, such as circles and blobs. This tool uses percentages so shapes remain proportional as they scale.

Related free tools

• CSS Box Shadow Generator — add layered depth to your rounded elements.
• CSS Clip Path Generator — cut elements into polygons and custom shapes.
• CSS Gradient Generator — build smooth color transitions for fills and backgrounds.
• CSS Formatter — tidy and indent your stylesheet in seconds.

Built by ByteVancer

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