CSS Flexible Box Layout Essentials

CSS Flexible Box Layout is a game-changer for web designers. It allows us to create flexible and responsive layouts with ease.

The Flexible Box Layout model is based on a box model, where each element is treated as a box with width, height, and margin properties. This makes it easy to create complex layouts with minimal code.

The main benefits of using Flexible Box Layout include improved responsiveness, easier layout management, and reduced code complexity. By using the Flexible Box Layout model, we can create layouts that adapt to different screen sizes and devices.

To get started with Flexible Box Layout, we need to define the display property of an element as flex or inline-flex. This will turn the element into a flexible container, allowing us to add child elements and manage their layout.

Flexbox is a one-dimensional layout model in CSS that's designed to provide a more efficient way to lay out, align, and distribute space among items in a container, even when their size is unknown or dynamic.

To start using Flexbox, you first need to define a flex container by setting the display property of an element to flex or inline-flex. This will make all its direct children automatically become flex items.

The main axis of a flex container is the primary axis along which flex items are laid out. It's not necessarily horizontal; it depends on the flex-direction property. Flex items are placed within the container starting from main-start and going to main-end.

Here's a summary of the main axis and cross axis terminology:

Flexbox is a whole module in CSS, not a single property, which means it involves a lot of things, including its own set of properties.

To understand how flexbox works, it's essential to know the terminology. A flex container is the parent element, also known as the "flex container", and its children are called "flex items."

Flex items will be laid out following either the main axis or the cross axis. The main axis is the primary axis along which flex items are laid out, and it's not necessarily horizontal; it depends on the flex-direction property.

The main-start and main-end terms refer to the placement of flex items within the container, starting from main-start and going to main-end.

A flex item's main size is its width or height, whichever is in the main dimension. The main size property is either the 'width' or 'height' property, whichever is in the main dimension.

Here are the key terms to keep in mind:

Understanding these terms will help you work with flexbox more efficiently and effectively.

The flex-basis property is a crucial part of CSS Flexible Box Layout, defining the default size of an element before the remaining space is distributed.

You can set flex-basis to a length, such as 20% or 5rem, or use a keyword like auto or content. The auto keyword means the browser will look at the width or height property of the element, while content means the element's size will be based on its content.

Setting flex-basis to 0 means the extra space around content isn't factored in, whereas setting it to auto means the extra space is distributed based on the flex-grow value.

The flex-basis property can also be used to set the initial main size of an item to a specific value, such as 200px.

To use flexbox, you need to declare that you want to use a flex formatting context by changing the value of the display property to flex. This will give you a block-level box with flex item children.

The initial values of flex items mean that they display as a row. They do not wrap, grow to fill the container, or line up anywhere other than at the start of the container.

Flex items immediately start exhibiting some flexbox behavior as soon as you declare a flex container, using their initial values.

Here are the initial values in a nutshell:

Item Properties are what make individual items within a flex container truly flexible. They allow you to control the layout of each item, making it easy to create complex and dynamic designs.

You can use flex item properties to control the size and position of each item, even when the container's layout changes. This is especially useful when working with responsive design.

Flex item properties are a powerful tool for creating custom layouts, and they're surprisingly easy to use. By understanding how to control individual items, you can create unique and engaging designs that stand out.

Item Properties are what make individual items within a flex container stand out. They allow you to control the layout and behavior of each item.

Flex item properties are used to control individual items within the container. This is in contrast to flex container properties, which control the overall layout.

You can use flex item properties to adjust the size and position of each item. This is especially useful when you have a mix of different sized items in the same container.

To set the size of an item, you can use the flex-basis property. This sets the initial size of the item before any flexing occurs.

Auto margins are used to add space around a specific element, and can even be used to center an element with margin: auto.

In some layout modes, like Flow and Positioned, the margin property can be used to add space around an element, but in Flexbox, auto margins are much more interesting.

Auto margins will gobble up the extra space in a Flexbox layout and apply it to the element's margin, giving us precise control over where to distribute the extra space.

A common header layout features the logo on one side, and some navigation links on the other side, which can be built using auto margins.

By giving the Corpatech logo margin-right: auto, we can gather up all of the extra space and force it between the 1st and 2nd item.

There are lots of other ways we could have solved this problem, but personally, I love the auto-margins solution because it treats the extra space as a resource and decides exactly where it should go.

You can control the direction of items in a flex layout by adding the flex-direction property and one of the four values: row, row-reverse, column, or column-reverse.

The initial value of flex-direction is row, so if you don't add the property, the items will display as a row. You can change the direction to column by adding flex-direction: column.

To distribute extra free space leftover in a flex layout, you can use the justify-content property. It helps pack items toward the start or end of the flex-direction, or center them along the line.

Here are the possible values for justify-content: flex-start, flex-end, center, space-between, space-around, and space-evenly. The safest values are flex-start, flex-end, and center, due to nuanced browser support.

To set both flex-direction and flex-wrap properties at once, you can use the flex-flow shorthand. For example, to set flex-direction to column and allow items to wrap, you can use flex-flow: column wrap.

Controlling the direction of items in a flex layout can be a bit tricky, but it's actually quite simple once you understand the basics. The initial value of flex-direction is row, which means items will display as a row by default.

To change the direction, you can add the flex-direction property and one of the four values: row, row-reverse, column, or column-reverse. The row value lays out items from left to right, while row-reverse does it from right to left. The column value lays out items from top to bottom, and column-reverse does it from bottom to top.

Here are the four values you can use for flex-direction:

By using these values, you can control the direction of your items and create a layout that suits your needs.

Creating a card layout with Flexbox is a great way to display content in a responsive and visually appealing way. Flexbox is perfect for creating flexible card layouts that adjust to different screen sizes.

As you can see in the example, a responsive card layout can adjust from three columns to two and then to one as the screen size decreases. This is achieved by using Flexbox's flexibility to adapt to different screen sizes.

You can use Flexbox to create a card layout that wraps items onto multiple lines if they don't fit in one line. The flex-wrap property allows you to change the default behavior of Flexbox, which is to keep all items on one line.

Here are the different values of the flex-wrap property:

By using the flex-wrap property, you can create a card layout that looks great on both small and large screens.

Justify-Content is a crucial property for controlling the layout of your web pages. It helps distribute extra free space leftover when either all the flex items on a line are inflexible, or are flexible but have reached their maximum size.

There are several values you can use for justify-content, including flex-start, which is the default and packs items toward the start of the flex-direction. You can also use flex-end, which packs items toward the end of the flex-direction.

The center value centers items along the line, while space-between evenly distributes items in the line with the first item on the start line and the last item on the end line.

Here are the different justify-content values in detail:

Note that browser support for these values is nuanced, so it's best to stick with the safest values, such as flex-start, flex-end, and center.

Layout Alignment is a crucial aspect of CSS Flexible Box Layout.

The align-items property defines how flex items are laid out along the cross axis, perpendicular to the main axis. It has several values, including stretch (the default), flex-start, flex-end, center, and baseline.

To vertically center flex items within a container, use the align-items property with a value of center. This will center the items in the cross-axis.

Flexbox brought with it a set of properties for aligning items and distributing space between items. These properties can be grouped into two categories: properties for space distribution and properties for alignment.

The properties used for alignment in flexbox are align-self and align-items. The align-self property aligns a single item on the cross axis, while the align-items property aligns all items as a group on the cross axis.

To align items on the cross-axis, use the align-items and align-self properties. The initial value of align-self is stretch, which is why flex items in a row stretch to the height of the tallest item by default.

Here are the values you can use to align items on the cross-axis:

To center an item vertically and horizontally, use the justify-content property to align the item on the main axis (row) and the align-items property on the cross axis.

You can control the space inside flex items by adjusting the flex-grow, flex-shrink, and flex-basis properties. The initial value of these properties is flex: initial, which means items do not grow and can shrink smaller than their flex-basis.

To make items grow and share space equally, use flex: auto, which sets the properties to flex-grow: 1, flex-shrink: 1, and flex-basis: auto. This allows large items to gain more space.

You can also force all items to be a consistent size by using flex: 1, which unpacks to flex-grow: 1, flex-shrink: 1, and flex-basis: 0. This means all items have zero size, and the space in the flex container is distributed equally among them.

Here's a summary of the possible values for the flex shorthand property:

Gaps are a game-changer for layout space. The gap property explicitly controls the space between flex items, and it applies that spacing only between items not on the outer edges.

This means you can create a minimum gutter between items, and if there's already space between them, the gap will only take effect if that space would end up smaller. The gap property works in grid and multi-column layout as well.

You can use gap to create space in-between each Flex child, which is great for things like navigation headers. This property has been implemented across all modern browsers since early 2021.

The gap property is a relatively new addition to the Flexbox language, but it's been a huge quality-of-life improvement for layout space.

Line spacing is a crucial aspect of layout space, and it's often overlooked. You can control line spacing by using the align-content property, which is similar to justify-content.

The initial value of align-content is stretch, meaning items will fill the available space. This can be changed by adding the align-content property to the flex container.

A wrapped flex container provides space to distribute on the cross axis, making it ideal for line spacing. This allows you to use the same values as justify-content for align-content.

Try using align-content in a demo to see the difference it makes.

Grow is a fundamental concept in CSS Flexible Box Layout, and it's essential to understand how to control it. The flex-grow property defines the ability for a flex item to grow if necessary, and it accepts a unitless value that serves as a proportion.

If all items have flex-grow set to 1, the remaining space in the container will be distributed equally to all children. This means that each item will take up an equal amount of space, resulting in a balanced layout.

In some cases, you might want one item to take up more space than the others. For example, if you set one item's flex-grow value to 2, it will take up twice as much space as the others.

You can also use flex-grow to create a layout where items grow at different rates. For instance, if you set one item's flex-grow value to 1, another to 2, and a third to 3, the available space in the container will be shared accordingly.

You can change the visual order of elements with Flexbox using the order property. This property allows you to reorder items without changing the HTML structure.

Flex items can be reordered using the order property, which controls the order in which they appear in the flex container. The lowest values come first, and if multiple items have the same value, they will be displayed together.

By default, flex items are laid out in the source order, but the order property can change that. Items with the same order value will revert to their original source order.

You can change the visual order of elements without changing the HTML structure using the order property.

Flexbox allows you to reorder items in your flex container using the order property. It's a simple way to control the order of elements.

Items are laid out in the direction dictated by flex-direction, with lowest values first. This means that the order of items can be changed by adjusting their order values.

Items with the same order value will be displayed together, reverting to source order if necessary. This can be useful when you need to group similar elements together.

The order property controls the order in which flex items appear in the flex container, overriding the source order. This is especially useful when you need to change the layout of your page without modifying the underlying HTML.

Using the flex property is a great way to simplify your CSS code, and it's recommended to use it instead of setting the individual properties. This shorthand property can save you time and effort in the long run.

The flex property is a shorthand for flex-grow, flex-shrink, and flex-basis combined. Setting it with a single number value, like flex: 5;, changes the flex-basis to 0%, making it equivalent to setting flex-grow: 5; flex-shrink: 1; flex-basis: 0%;.

You can use the flex property with optional parameters, such as flex-shrink and flex-basis, which have default values of 0 1 auto.

Flexbox is a powerful tool for creating flexible layouts, but it's essential to use it effectively. Start with a Good HTML Structure, grouping related items under a common parent, just like in the example of the list of 6 items with fixed dimensions.

Use Flexbox for One-Dimensional Layouts, as it's designed for either rows or columns. For complex two-dimensional layouts, consider using CSS Grid. Flexbox can also be combined with other layout techniques, like position or float, for specific elements.

Here are some key best practices to keep in mind:

Reversing the flow of items can negatively impact accessibility. This is because the logical order of content is different from the visual order, and screen readers and keyboard navigation follow the logical order.

The row-reverse and column-reverse values in flexbox and grid can cause this problem. These values only reorder the visual display, not the logical order.

You should be cautious when using these properties and thoroughly test your site to ensure it remains accessible for everyone.

Reversing the order of items can make it hard for people to navigate your site using a keyboard. This is because keyboard navigation follows the DOM, not the visual display.

For example, in a reversed row layout, tabbing between links becomes disconnected. This is because the keyboard navigation is following the logical order of the content, not the visual order.

To make the most of Flexbox, keep these best practices in mind. Start with a good HTML structure, as Flexbox works best when you have a clear parent-child relationship in your HTML.

Use Flexbox for one-dimensional layouts, either rows or columns. For complex two-dimensional layouts, consider using CSS Grid. Flexbox doesn't have to be used in isolation, it can work well alongside other CSS layout properties like position or float for specific elements.

Be mindful of flex-basis when using flex-grow and flex-shrink. Setting an appropriate flex-basis can make your layouts more predictable.

Use shorthand properties, like the flex shorthand property (flex: 1 1 auto), which is more concise and often easier to manage than setting flex-grow, flex-shrink, and flex-basis separately.

To ensure accessibility, reorder elements with Flexbox so that the visual order matches the logical order in the HTML for screen readers.

Flexbox is incredibly useful for achieving perfect centering, and it's as simple as setting a margin to auto in a flex container. This makes the item perfectly centered in both axes.

You can also use flexbox to evenly distribute items on the horizontal axis, making it easy to create responsive layouts that scale nicely with the browser size. For example, a list of 6 items with fixed dimensions can be auto-sized and evenly distributed without the need for media queries.

Imagine you have a right-aligned navigation element on the top of your website, but you want it to be centered on medium-sized screens and single-columned on small devices. Flexbox makes this easy to achieve.

Flexbox can also be used to create complex layouts, such as a mobile-first 3-columns layout with a full-width header and footer.

By default, a flex container wraps children. This means that the children will automatically be placed on the same line, making it easy to create horizontal layouts.

Flex children can appear squished, but setting the flex property can help mitigate this issue. The flex property allows you to distribute the space in the container among the children, making them appear more evenly spaced.

Flex containers are great for creating responsive layouts, as they can adapt to different screen sizes and devices.