---
title: border
slug: Web/CSS/border
tags:
  - CSS
  - CSS Borders
  - CSS Property
  - Layout
  - Reference
translation_of: Web/CSS/border
---
<div>{{CSSRef("CSS Borders")}}</div>

<p><span class="seoSummary"><strong><code>border</code></strong> <a href="/en-US/docs/Web/CSS/Shorthand_properties">shorthand</a> <a href="/en-US/docs/CSS">CSS</a> 屬性可用來設定元素的邊框。</span>它可以設定以下的值 {{Cssxref("border-width")}}、{{Cssxref("border-style")}} 以及 {{Cssxref("border-color")}}。</p>

<div>{{EmbedInteractiveExample("pages/css/border.html")}}</div>



<p>As with all shorthand properties, any omitted sub-values will be set to their <a href="/en-US/docs/Web/CSS/initial_value">initial value</a>. Importantly, <code>border</code> cannot be used to specify a custom value for {{cssxref("border-image")}}, but instead sets it to its initial value, i.e., <code>none</code>.</p>

<p>The <code>border</code> shorthand is especially useful when you want all four borders to be the same. To make them different from each other, however, you can use the longhand {{Cssxref("border-width")}}, {{Cssxref("border-style")}}, and {{Cssxref("border-color")}} properties, which accept different values for each side. Alternatively, you can target one border at a time with the physical (e.g., {{Cssxref("border-top")}} ) and logical (e.g., {{Cssxref("border-block-start")}}) border properties.</p>

<h3 id="Borders_vs._outlines">Borders vs. outlines</h3>

<p>Borders and <a href="/en-US/docs/Web/CSS/outline">outlines</a> are very similar. However, outlines differ from borders in the following ways:</p>

<ul>
 <li>Outlines never take up space, as they are drawn outside of an element's content.</li>
 <li>According to the spec, outlines don't have to be rectangular, although they usually are.</li>
</ul>

<h2 id="Syntax" name="Syntax">Syntax</h2>

<pre class="brush: css no-line-numbers">/* style */
border: solid;

/* width | style */
border: 2px dotted;

/* style | color */
border: outset #f33;

/* width | style | color */
border: medium dashed green;

/* Global values */
border: inherit;
border: initial;
border: unset;
</pre>

<p>The <code>border</code> property may be specified using one, two, or three of the values listed below. The order of the values does not matter.</p>

<div class="note">
<p><strong>Note:</strong> The border will be invisible if its style is not defined. This is because the style defaults to <code>none</code>.</p>
</div>

<h3 id="Values" name="Values">Values</h3>

<dl>
 <dt id="&lt;line-width>"><code>&lt;line-width&gt;</code></dt>
 <dd>Sets the thickness of the border. Defaults to <code>medium</code> if absent. See {{Cssxref("border-width")}}.</dd>
 <dt id="&lt;line-style>"><code>&lt;line-style&gt;</code></dt>
 <dd>Sets the style of the border. Defaults to <code>none</code> if absent. See {{Cssxref("border-style")}}.</dd>
 <dt id="&lt;color>">{{cssxref("&lt;color&gt;")}}</dt>
 <dd>Sets the color of the border. Defaults to <code>currentcolor</code> if absent. See {{Cssxref("border-color")}}.</dd>
</dl>

<h3 id="Formal_syntax">Formal syntax</h3>

<pre class="syntaxbox"><code>{{csssyntax}}</code></pre>

<h2 id="Example">Example</h2>

<h3 id="HTML">HTML</h3>

<pre class="brush: html">&lt;div&gt;I have a border, an outline, AND a box shadow! Amazing, isn't it?&lt;/div&gt;
</pre>

<h3 id="CSS">CSS</h3>

<pre class="brush: css">div {
  border: 0.5rem outset pink;
  outline: 0.5rem solid khaki;
  box-shadow: 0 0 0 2rem skyblue;
  border-radius: 12px;
  font: bold 1rem sans-serif;
  margin: 2rem;
  padding: 1rem;
  outline-offset: 0.5rem;
}</pre>

<h3 id="Result">Result</h3>

<p>{{EmbedLiveSample('Example')}}</p>

<h2 id="Specifications" name="Specifications">Specifications</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('CSS3 Backgrounds', '#the-border-shorthands', 'border')}}</td>
   <td>{{Spec2('CSS3 Backgrounds')}}</td>
   <td>Removes <em>specific</em> support for <code>transparent</code>, as it is now a valid {{cssxref("&lt;color&gt;")}}; this has no practical impact.<br>
    Though it cannot be set to a custom value using the shorthand, <code>border</code> now resets {{cssxref("border-image")}} to its initial value (<code>none</code>).</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS2.1', 'box.html#border-shorthand-properties', 'border')}}</td>
   <td>{{Spec2('CSS2.1')}}</td>
   <td>Accepts the <code>inherit</code> keyword. Also accepts <code>transparent</code> as a valid color.</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS1', '#border', 'border')}}</td>
   <td>{{Spec2('CSS1')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<p>{{cssinfo}}</p>

<h2 id="Browser_compatibility" name="Browser_compatibility">Browser compatibility</h2>



<p>{{Compat("css.properties.border")}}</p>