Adjust border-radius values for each corner visually and copy the CSS output.
Drag each corner radius slider to shape the border radius.
See the live preview update as you change each corner value.
Click copy to grab the border-radius CSS property for your code.
This tool draws a box with a control at each of its four corners. Adjust any corner, the box redraws, and a panel beside it shows the border-radius declaration ready to copy into a stylesheet. The corner most people get wrong is the order: the shorthand lists corners clockwise from the top-left (top-left, top-right, bottom-right, bottom-left), so the third value you paste belongs to the bottom-right corner, not the bottom-left. The preview shows what the declaration will render, so what you see on the box is what you get in the browser.
A concrete input and expected output from the current implementation.
Input
Enter 24 into the top-left control, 8 into top-right, 16 into bottom-right, and 4 into bottom-left
Expected output
border-radius: 24px 8px 16px 4px;
The four-value shorthand is read clockwise starting from the top-left corner, so each number lands exactly on the corner it was set for: 24 top-left, 8 top-right, 16 bottom-right, 4 bottom-left.
Each corner has its own control, so the four radii are independent; changing one leaves the other three untouched. The preview box re-renders with every change, and the declaration beside it updates at the same time. That independence is what the tool is for: asymmetric shapes such as a chat bubble tail, a tab, or a badge, where one corner differs from the rest.
The panel shows the declaration in the standard shorthand, which browsers read clockwise from the top-left corner. Copying puts the text on your clipboard to paste into a stylesheet. The shorthand accepts one to four values, so four equal numbers are valid but not minimal - the corners render the same either way. All of this happens locally in the page; your values are never sent anywhere.
Percentages resolve against the box's width and height independently, so on a rectangle, 50% on every corner produces an ellipse, not a circle. A true circle needs equal width and height, or a large fixed pixel radius on a square. The tool's preview runs the same math the browser does, so the ellipse you see is the correct rendering, not a glitch.
Set every corner to at least half the element's height, or to a very large value such as 9999px. Adjacent radii whose sum exceeds the side length are scaled down proportionally by the browser, so the ends render as semicircles. Half the height is enough and keeps the value readable; larger values clamp to the same visual result.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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