columnrulewidth

Column-rule-width is a CSS property used in multi-column layouts to specify the thickness of the vertical rule that separates columns. It is part of the CSS Multi-column Layout Module and works with column-rule, column-rule-style, and column-rule-color to render the dividing line between columns. The width can be set with a length value or with the keywords thin, medium, or thick.

The initial value is medium. The property is not inherited by default, but it can be inherited by explicitly using the inherit value. The rule is visible only if column-rule-style is not none; a color is applied via column-rule-color, and the line style via column-rule-style determines how the rule is drawn (for example solid, dashed, or double).

Syntax: column-rule-width: <length> | thin | medium | thick | initial | inherit.

Examples:

- p { column-count: 3; column-rule-width: 2px; column-rule-style: solid; column-rule-color: #333; }

- section { column-count: 2; column-rule-width: thin; column-rule-style: solid; }

Compatibility: Supported in modern browsers including Chrome, Firefox, Safari, and Edge. It applies to elements that use a multi-column layout (via column-count or column-width). Notes: the keywords map to approximate widths and may vary by user agent. The property can be overridden by other layout features such as borders, so careful interaction with column-rule is recommended.