In frontend development, both border-radius: 50% and border-radius: 100% create rounded corners, but there's a subtle difference that often goes unnoticed. Both values create a circular border, but 100% can sometimes lead to clipping issues in more complex scenarios, especially with elliptical shapes or non-uniform padding/borders.
Here's a breakdown:
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border-radius: 50%: This value is sufficient to create a perfect circle or ellipse. It takes the smaller dimension (height or width) of the element and uses 50% of that value as the radius. This ensures the corners are rounded to the maximum extent possible without exceeding the element's dimensions. -
border-radius: 100%: This value can also create a perfect circle or ellipse, but it uses 100% of the smaller dimension as the radius. While seemingly redundant, the key difference lies in how this interacts with other properties like padding, borders, and especially elliptical shapes. Because the radius is larger than necessary, it can sometimes lead to clipping where the rounded corners are cut off, particularly in elements with unequal width and height.
In simpler terms:
Imagine a square. Both 50% and 100% will create a perfect circle.
Now imagine a rectangle. Both will create an ellipse, but if the rectangle is very narrow, border-radius: 100% might cause the rounded corners to be slightly clipped, whereas 50% will always produce a smooth, unclipped ellipse.
Best Practice:
For creating circular or elliptical shapes, border-radius: 50% is generally recommended. It's simpler, more efficient, and avoids potential clipping issues. Using 100% doesn't offer any visual advantages and can introduce subtle problems.
Example demonstrating the clipping issue (rare but possible):
Consider an element with significant padding and a border-radius: 100%. The excessive radius might cause the curve of the rounded corner to be clipped by the padding, resulting in a less smooth appearance. This is less likely to happen with 50%.
Therefore, while both values often produce the same visual result in simple cases, sticking to border-radius: 50% is the safer and more predictable approach for creating rounded shapes in CSS.