Master the 8-Value Border Radius
Most developers only use the standard 4-value border-radius for simple rounded rectangles. Our Advanced CSS Border Radius Builder unlocks the hidden 8-value syntax, allowing you to create complex, fluid, and asymmetrical "blob" shapes purely with CSS.
Understanding the Slash (/) Syntax
The secret to organic CSS shapes is defining separate horizontal and vertical radii. The syntax looks like this: border-radius: 50% 50% 50% 50% / 60% 40% 40% 60%;
- Before the slash: Controls the horizontal stretching of the corners.
- After the slash: Controls the vertical stretching of the corners.
- By dragging the handles on our visual builder, the tool mathematically calculates these percentages for you, generating the perfect shape instantly.
How to Use This Tool
- Upload or Input Data: Select your file or paste your data directly into the tool interface. Everything remains on your device.
- Configure & Process: Adjust any optional settings if necessary. The tool will process your data instantly inside your browser.
- Download Result: Preview the output and click the download or copy button to save your final results.
Frequently Asked Questions
Are CSS blobs better than SVG?
For simple decorative backgrounds or profile picture masks, a CSS blob is much lighter and requires zero additional HTTP requests compared to an SVG file.
How can I animate the blob?
Generate two different blob shapes with the tool, copy their output, and place them inside a CSS `@keyframes` animation to transition infinitely between the two states.
Does it cause performance issues?
No, `border-radius` is heavily optimized by modern browser rendering engines and performs excellently, even on mobile devices.