border-top-left-radius - CSS: Cascading Style Sheets 编辑

The border-top-left-radius CSS property rounds the top-left corner of an element by specifying the radius (or the radius of the semi-major and semi-minor axes) of the ellipse defining the curvature of the corner.

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The rounding can be a circle or an ellipse, or if one of the value is 0,no rounding is done and the corner is square.

A background, being an image or a color, is clipped at the border, even a rounded one; the exact location of the clipping is defined by the value of the background-clip property.

Syntax

/* the corner is a circle */
/* border-top-left-radius: radius */
border-top-left-radius: 3px;

/* the corner is an ellipse */
/* border-top-left-radius: horizontal vertical */
border-top-left-radius: 0.5em 1em;

border-top-left-radius: inherit;

With one value:

• the value is a <length> or a <percentage> denoting the radius of the circle to use for the border in that corner.

With two values:

• the first value is a <length> or a <percentage> denoting the horizontal semi-major axis of the ellipse to use for the border in that corner.
• the second value is a <length> or a <percentage> denoting the vertical semi-major axis of the ellipse to use for the border in that corner.

Values

<length-percentage>

Denotes the size of the circle radius or the semi-major and semi-minor axes of the ellipse. As absolute length it can be expressed in any unit allowed by the CSS <length> data type. Percentages for the horizontal axis refer to the width of the box, percentages for the vertical axis refer to the height of the box. Negative values are invalid.

Formal definition

Formal syntax

<length-percentage>{1,2}
where 
<length-percentage> = <length> | <percentage>

Examples

Examples of different border-top-left-radius values

div {
  border-top-left-radius: 40px 40px;
}

div {
  border-top-left-radius: 40px 20px;
}

div {
  border-top-left-radius: 40%;
}

div {
  border-top-left-radius: 40%;
}

div {
  border-top-left-radius:40%;
  border-style: black 3px double;
  background-color: rgb(250,20,70);
  background-clip: content-box;
}

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• border-radius shorthand property
• border-top-right-radius, border-bottom-right-radius, and border-bottom-left-radius