CSS Multi-column Layout

The CSS Multi-column Layout standard is a CSS module that adds support for multi-column layouts to CSS. This module makes it easier and more reliable than ever to produce columnar layouts without having to hand-code complicated and fragile structures. Support is included for establishing the number of columns in a layout, as well as how content should flow from column to column, gap sizes, column dividing lines (known as column rules), and so forth.

The three key properties used to produce the layout of columns in CSS are column-count (en-US), column-width (en-US), and column-gap (en-US). Other properties provide ways to fine-tune details of how things are organized and rendered within the layout structure built using those properties, but the job of figuring out what goes where is generally handled by these four.

The first two properties, column-count and column-width, are both the most important and the most potentially misleading. It's important to understand that:

• The column-count (en-US) property specifies a maximum number of columns to use to render the text. The browser will consider the amount of horizontal space available, the value of column-width, and the value of column-gap, then draw the largest number of columns across that it can fit into the available space.
• The column-width (en-US) property specifies a minimum column width, given a length (en-US) value. Each column the browser creates will be at least this wide, but may be wider. After determining the number of columns that it will draw, any remaining horizontal space may be divided up by the browser among the columns  and added to their widths.

In a way, then, they're more like recommendations than hard and fast rules. And this makes sense once you consider the logic of it; this allows multi-column layouts to be responsive and adaptive to the screen width, while also supporting the overall layout of the page and the intent of the author. As the width of the containing space (or the screen) shrinks, the browser will reduce the number of columns it creates, adjusting the remaining columns' widths to ensure that the overall width is as expected.

The other thing you can control is the distance between the columns, known as the column gap. The column gap can be controlled using the column-gap (en-US) property. By convention, the default gap is 1em, but this may or may not be the case in any given browser, so if it matters to you, explicitly set it. The column  gap, unlike the column count and width, doesn't get adjusted by the browser as it tries to fit the content into the available space.

Take a look at the example below, in which you can use the range control at the top to adjust the width of the columns' containing element.

The column-fill (en-US) property also affects layout. By default, the browser will create as many appropriately-sized columns as it can, then balance the contents across them so that each column is approximately the same length. If, however, you prefer to have the browser fill the first column to its maximum height before moving on to the next column, you can set column-fill to auto (instead of the default, balance).

If there is no constraint on the column height, however, there will only be one column created, as it will never reach its maximum height to trigger wrapping to the second column, so be sure to either place your columns inside a container which constrains their height, either by using height or max-height (en-US).

You can specify that a column rule—a dividing line drawn in the center of each column gap—be drawn between each column in the rendered output of your layout by using the column-rule-style (en-US), column-rule-width (en-US), and column-rule-color (en-US) properties, or the shorthand property column-rule (en-US).

Using CSS multi-column layouts

Step-by-step tutorial about how to build layouts using several columns.

Other CSS layout technologies include:

• CSS Flexible box layout (CSS flexbox)
• CSS Grid layout