CSS border-image-outset
The border-image-outset property is one of the properties introduced in CSS3 for the purposes of enabling images to be used on CSS borders.
The CSS border-image-outset property is used for defining how much a border image area extends beyond the border box.
The border-image-outset property is used in conjunction with the border-image-source, border-image-slice, border-image-width, and border-image-repeat properties in order to determine how the image will appear on the border.
Note that setting an image border will override any border that has been specified using the border-style properties. However, if the image cannot be loaded, or if the border-image-source value is none, the border styles will be used instead.
To save time (and use less code), use the border-image property to set all your background image properties at once.
The examples on this page include browser-specific properties that start with extensions such as -webkit-, -moz-, etc. This is for browser compatibility reasons. See the bottom of this article for more on this.
| Syntax: | The formal grammar for this property is: border-image-outset: [ <length> | <number> ]{1,4}
Below are some examples of usage. One-Value SyntaxTo set all four sides at once: border-image-outset: value
Example:
Two-Value SyntaxTo specify the horizontal and vertical values separately: border-image-outset: horizontal vertical
Example: Three-Value SyntaxTo specify the top, vertical, and bottom values separately: border-image-outset: top vertical bottom
Example: Four-Value SyntaxTo specify all four sides separately: border-image-outset: top right bottom left
Example: Inherit SyntaxTo inherit the values: border-image-outset: inherit
For more information, see the Possible Values section below. |
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| Example |
Note that this example includes various CSS extensions in addition to the W3C CSS3 property. This is for browser compatibility.
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| Try it yourself! |
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| Possible Values: |
If this property has four values, they set the outsets on the top, right, bottom and left sides respectively. If the left is missing, it is the same as the right; if the bottom is missing, it is the same as the top; if the right is missing, it is the same as the top. For more information, see the Syntax section above. |
| Initial Value: | 0
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| Applies to: | All elements, except internal table elements when border-collapse is collapse
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| Inherited: | No |
| Media: | Visual |
Browser Compatibility
At the time of writing, CSS3 was still under development and browser support for many CSS3 properties was limited or non-existent. For maximum browser compatibility many web developers add browser-specific properties by using extensions such as -webkit- for Safari and Google Chrome, -ms- for Internet Explorer, -moz- for Firefox, -o- for Opera etc. As with any CSS property, if a browser doesn't support a proprietary extension, it will simply ignore it.
This practice is not recommended by the W3C, however in many cases, the only way you can test a property is to include the CSS extension that is compatible with your browser.
Be aware that if you choose to use the proprietary CSS extensions in a live environment, your code will not pass any W3C CSS validation, as the browser-specific properties are not valid W3C properties.
Many of the CSS3 examples on this website include these browser specific properties. If they weren't included, most of the examples wouldn't work for most users (at least, not until possibly years after the article was written).
The major browser manufacturers are working to support the W3C properties, and eventually, you will be able to omit these browser-specific properties.