Flexbox is a layout mode of CSS, suitable for alignment and distribution of one-dimensional space. 1. Create a Flex container through display: flex, and the child elements automatically become elastic items, arranged in a row by default; 2. Use flex-direction to set the spindle direction (such as row or column); 3. Justify-content to control the alignment on the spindle (such as center, space-between); 4. align-items to control the alignment on the cross axis (such as center, stretch); 5. flex-wrap allows project line breaks; 6. flex-grow, flex-shrink and flex-basis to control the scaling behavior of the project. When using it, be careful to only affect direct child elements, avoid excessive nesting, consider browser compatibility and high control issues. Mastering these properties allows you to achieve flexible and responsive layouts.
Flexbox is a powerful layout tool in CSS, especially suitable for handling the alignment and distribution of one-dimensional space. It makes it easier for developers to design flexible, responsive page structures without relying on traditional methods such as floating or positioning.

What is Flexbox?
Flexbox is a CSS layout mode. By setting the container to display: flex
, children can automatically resize and position according to the available space. It is especially suitable for building interface components such as navigation bars, card layouts, button groups, etc.

How to create a Flex container?
Simply set display
property of the container element to flex
or inline-flex
:
.container { display: flex; }
This way, all direct child elements of the container become "elastic items" and are lined up by default.

Common settings include:
-
flex-direction
: controls the spindle direction (row
,row-reverse
,column
,column-reverse
) -
justify-content
: Controls the alignment on the spindle -
align-items
: controls the alignment on the cross axis
These properties determine how and where the items are arranged in the container.
What are the main Flexbox properties? How to use it?
1. flex-direction
Determines the direction of the spindle, the default is row
(from left to right). If you want to arrange vertically, you can use column
.
.container { flex-direction: column; }
2. justify-content
Used to align items on the spindle. Commonly used values are:
-
flex-start
(default) -
center
-
flex-end
-
space-between
-
space-around
For example, using space-between
can make the first and last items be edged separately, and the middle items are evenly distributed.
3. align-items
Used to align items on cross axis. Commonly used values are similar to those above, such as center
, flex-start
, flex-end
, and stretch
(default).
4. flex-wrap
By default, all items are displayed on one line. If there is too much content, you can set a line break:
.container { flex-wrap: wrap; }
In this way, items that exceed the width will be automatically wrapped.
5. flex-grow
, flex-shrink
, flex-basis
These three properties control the scaling behavior of a single project:
-
flex-grow
: Defines how the project stretches and fills the remaining space -
flex-shrink
: Define how the project is compressed to accommodate insufficient space -
flex-basis
: defines the initial size of the project before allocating excess space
Usually we will abbreviate it as flex: grow shrink basis;
, for example:
.item { flex: 1 1 auto; }
This means that the project will automatically scale based on the space.
What should be paid attention to in practical applications?
Although Flexbox is powerful, there are some error-prone places:
- Affects only direct child elements : Flexbox's layout rules only apply to direct child elements of the container, and deeper nested elements are not automatically controlled.
- Use
flex-wrap
and height control with caution : If line wrap is enabled, be careful when setting the container height. - Browser Compatibility : Although modern browsers support Flexbox, older versions such as IE10 and below require vendor prefix.
- Avoid over-necking : While nesting Flex containers is feasible, too much nesting can make the structure complex and difficult to maintain.
Basically that's it. After mastering these key attributes, you can meet most common layout needs.
The above is the detailed content of Understanding CSS Flexbox properties and layout. For more information, please follow other related articles on the PHP Chinese website!

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