<pre class="brush: css notranslate"><code><span class="token comment">/ &lt;length&gt; value /</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> 1rem<span class="token punctuation">;</span> <span class="token comment">/ &lt;number&gt; value /</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> 1.5<span class="token punctuation">;</span> <span class="token comment">/ vertical | horizontal /</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> 1 1.2<span class="token punctuation">;</span> <span class="token comment">/ top | horizontal | bottom /</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> 30px 2 45px<span class="token punctuation">;</span> <span class="token comment">/ top | right | bottom | left /</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> 7px 12px 14px 5px<span class="token punctuation">;</span> <span class="token comment">/ Global values /</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> inherit<span class="token punctuation">;</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> initial<span class="token punctuation">;</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> revert<span class="token punctuation">;</span> <span class="token property">mask-border-outset</span><span class="token punctuation">:</span> unset<span class="token punctuation">;</span> </code></pre>

mask-border-outset

The mask-border-outset CSS property specifies the distance by which an element's mask border is set out from its border box.

Syntax

/* <length> value */ mask-border-outset: 1rem;  /* <number> value */ mask-border-outset: 1.5;  /* vertical | horizontal */ mask-border-outset: 1 1.2;  /* top | horizontal | bottom */ mask-border-outset: 30px 2 45px;  /* top | right | bottom | left */ mask-border-outset: 7px 12px 14px 5px;  /* Global values */ mask-border-outset: inherit; mask-border-outset: initial; mask-border-outset: revert; mask-border-outset: unset; 

The mask-border-outset property may be specified as one, two, three, or four values. Each value is a <length> or <number>. Negative values are invalid.

Values

The size of the mask border outset as a dimension.

The size of the mask border outset as a multiple of the corresponding border-width.

Formal definition

Formal syntax

[ <length> | <number> ]{1,4}

Examples

Basic usage

This property doesn't appear to be supported anywhere yet. When it eventually starts to be supported, it will serve to move the mask away from the inner edge of the element's border box — you can use it to make the mask start from part way across the border, rather than the inside of it.

mask-border-outset: 1rem; 

Chromium-based browsers support an outdated version of this property — mask-box-image-outset — with a prefix:

-webkit-mask-box-image-outset: 1rem; 

Note: The mask-border page features a working example (using the out-of-date prefixed border mask properties supported in Chromium), so you can get an idea of the effect.

Specifications

See also

Last modified: Aug 12, 2021, by MDN contributors