The border is a thin layer between padding and margin. Editing the border you can make elements draw their perimeter on screen.

You can work on borders by using those properties:

• border-style
• border-color
• border-width

The property border can be used as a shorthand for all those properties.

border-radius is used to create rounded corners.

You also have the ability to use images as borders, an ability given to you by border-image and its specific separate properties:

• border-image-source
• border-image-slice
• border-image-width
• border-image-outset
• border-image-repeat

Let’s start with border-style.

The border style

The border-style property lets you choose the style of the border. The options you can use are:

• dotted

• dashed
• solid
• double
• groove
• ridge
• inset
• outset
• none
• hidden

Check this Codepen for a live example

The default for the style is none, so to make the border appear at all you need to change it to something else. solid is a good choice most of the times.

You can set a different style for each edge using the properties

• border-top-style
• border-right-style
• border-bottom-style
• border-left-style

or you can use border-style with multiple values to define them, using the usual Top-Right-Bottom-Left order:

p {
  border-style: solid dotted solid dotted;
}

The border width

border-width is used to set the width of the border.

You can use one of the pre-defined values:

• thin
• medium (the default value)
• thick

or express a value in pixels, em or rem or any other valid length value.

Example:

p {
  border-width: 2px;
}

You can set the width of each edge (Top-Right-Bottom-Left) separately by using 4 values:

p {
  border-width: 2px 1px 2px 1px;
}

or you can use the specific edge properties border-top-width, border-right-width, border-bottom-width, border-left-width.

The border color

border-color is used to set the color of the border.

If you don’t set a color, the border by default is colored using the color of the text in the element.

You can pass any valid color value to border-color.

Example:

p {
  border-color: yellow;
}

You can set the color of each edge (Top-Right-Bottom-Left) separately by using 4 values:

p {
  border-color: black red yellow blue;
}

or you can use the specific edge properties border-top-color , border-right-color , border-bottom-color , border-left-color .

The border shorthand property

Those 3 properties mentioned, border-width, border-style and border-color can be set using the shorthand property border.

Example:

p {
  border: 2px black solid;
}

You can also use the edge-specific properties border-top, border-right, border-bottom, border-left.

Example:

p {
  border-left: 2px black solid;
  border-right: 3px red dashed;
}

The border radius

border-radius is used to set rounded corners to the border. You need to pass a value that will be used as the radius of the circle that will be used to round the border.

Usage:

p {
  border-radius: 3px;
}

You can also use the edge-specific properties border-top-left-radius, border-top-right-radius, border-bottom-left-radius, border-bottom-right-radius.

Using images as borders

One very cool thing with borders is the ability to use images to style them. This lets you go very creative with borders.

We have 5 properties:

• border-image-source
• border-image-slice
• border-image-width
• border-image-outset
• border-image-repeat

and the shorthand border-image. I won’t go in much details here as images as borders would need a more in-depth coverage as the one I can do in this little chapter. I recommend reading the CSS Tricks almanac entry on border-image for more information.