CSS border-collapse

<!doctype html>
<title>Example</title>
<style>
table {
  border: 1px solid orange;
  border-collapse: collapse;
  width: 100%;
  }
td, th {
  border: 1px solid orange;
  padding: 5px;
  }
</style>
<table>
  <tr>
    <th>Table Header</th>
    <th>Table Header</th>
    <th>Table Header</th>
  </tr>
  <tr>
    <td>Cell</td>
    <td>Cell</td>
    <td>Cell</td>
  </tr>
  <tr>
    <td>Cell</td>
    <td>Cell</td>
    <td>Cell</td>
  </tr>
</table>
<p>The above table is styled using <code>border-collapse:collapse</code>. Try changing the value to <code>border-collapse:separate</code> to see the effect it has on the borders. </p>

The CSS border-collapse property allows you to collapse a table's border.

By default, an HTML table uses the "separated borders model". This results in a kind of "double border" effect where there's space between the borders of each cell, as well as the edge of the table (if you also have a border on the table element).

You can use the border-collapse property to switch to the "collapsed borders model". This effectively collapses the borders into one border. So instead of seeing a "double border" you see a single border.

Syntax

Possible Values

collapse: Specifies that the collapsed border model should be used.
separate: Specifies that the separated border model should be used.

In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:

initial: Represents the value specified as the property's initial value.
inherit: Represents the computed value of the property on the element's parent.
unset: This value acts as either inherit or initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.

General Information

Initial Value: separate
Applies To: Table-root boxes (tables or inline-table boxes).
Inherited?: Yes
Media: Visual
Animation Type: Discrete

Example Code

Official Specifications

CSS Table Module Level 3 (W3C First Public Working Draft, 25 October 2016)
CSS Level 2.1 (W3C Recommendation 07 June 2011)