Best Free Online Developer Tools to Use in 2026
A practical, opinionated list of the best free online developer tools worth using in 2026, organized by category so you can find what you need fast.
Aug 08, 2026
Border Radius Generator
Create custom CSS border-radius values visually. Adjust each corner independently, apply preset shapes, and copy the generated CSS.
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What is Border Radius?
The CSS border-radius property rounds the corners of an element's outer border edge. You can set a single radius for all four corners or specify each corner individually.
This tool features:
- Real-time preview — See the border radius update instantly as you adjust controls.
- Per-corner control — Adjust each corner independently or link them together.
- Preset shapes — Start from common shapes like circle, pill, squircle, and more.
- Copy CSS — Export the generated
border-radiuscode with one click.
How to Use
- Choose a preset or start from scratch — Select a preset shape to see common border-radius styles, or adjust the sliders directly.
- Customize each corner — Toggle Link all corners to control each corner individually, or keep it linked for uniform rounding.
- Copy the CSS — Click Copy CSS to copy the generated
border-radiusproperty to your clipboard.
Frequently Asked Questions
What is the difference between px and % for border-radius?
Pixel values create fixed-radius corners. Percentage values create elliptical corners relative to the element's dimensions, which can produce oval or pill shapes when the element is not a perfect square.
How do I make a circle?
Set all four corners to 50% on a square element (equal width and height). The Circle preset does this automatically for you.
Is this tool free to use?
Yes. All processing happens entirely in your browser. No data is sent to any server.
Last updated: 17 Aug 2026
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