justify-content

start

The items are packed flush to each other toward the start edge of the alignment container in the main axis.

end

The items are packed flush to each other toward the end edge of the alignment container in the main axis.

flex-start

The items are packed flush to each other toward the edge of the alignment container depending on the flex container's main-start side. This only applies to flex layout items. For items that are not children of a flex container, this value is treated like start.

flex-end

The items are packed flush to each other toward the edge of the alignment container depending on the flex container's main-end side. This only applies to flex layout items. For items that are not children of a flex container, this value is treated like end.

center

The items are packed flush to each other toward the center of the alignment container along the main axis.

left

The items are packed flush with each other toward the left edge of the alignment container. When the property's horizontal axis is not parallel with the inline axis, such as when flex-direction: column; is set, this value behaves like start.

right

The items are packed flush to each other toward the right edge of the alignment container in the appropriate axis. If the property's axis is not parallel with the inline axis (in a grid container) or the main-axis (in a flexbox container), this value behaves like start.

normal

Behaves as stretch, except in the case of multi-column containers with a non-auto column-width, in which case the columns take their specified column-width rather than stretching to fill the container. As stretch behaves as start in flex containers, normal also behaves as start.

space-between

The items are evenly distributed within the alignment container along the main axis. The spacing between each pair of adjacent items is the same. The first item is flush with the main-start edge, and the last item is flush with the main-end edge.

space-around

The items are evenly distributed within the alignment container along the main axis. The spacing between each pair of adjacent items is the same. The empty space before the first and after the last item equals half of the space between each pair of adjacent items. If there is only one item, it will be centered.

space-evenly

The items are evenly distributed within the alignment container along the main axis. The spacing between each pair of adjacent items, the main-start edge and the first item, and the main-end edge and the last item, are all exactly the same.

stretch

If the combined size of the items along the main axis is less than the size of the alignment container, any auto-sized items have their size increased equally (not proportionally), while still respecting the constraints imposed by max-height/max-width (or equivalent functionality), so that the combined size exactly fills the alignment container along the main axis.

Note: For flexboxes, the stretch value behaves as flex-start or start. This is because, in flexboxes, stretching is controlled using the flex-grow property.

safe

If the item overflows the alignment container, then the item is aligned as if the alignment mode is start. The desired alignment will not be implemented.

unsafe

Even if the item overflows the alignment container, the desired alignment will be implemented. Unlike safe, which will ignore the desired alignment in favor of preventing overflow.

Defined in the CSS box alignment module, justify-content applies to multicol containers, flex containers, and grid containers. The property does not apply to and has no effect on block containers.

This property shares many keyword values with the align-content property, but not all! justify-content isn't involved in baseline alignment, and therefore does not take baseline values.

In flex layouts, the property defines how positive free space is distributed between or around flex items along the main axis. This property impacts the space between elements in a line, not the space between lines. The alignment is done after the lengths and auto margins are applied, which means that when one or more flex items in a line have a flex-grow factor greater than 0, the property has no effect as there is no space to distribute along that line. Also, as stretching along the main axis is controlled by flex, the stretch value behaves as flex-start.

With grid layout, this property distributes available space between or around grid columns, not grid items. If the grid container is larger than the grid itself, the justify-content property can be used to justify the grid along the inline axis, aligning the grid columns.

Grid auto track sizes (and only auto track sizes) can be stretched by the align-content and justify-content properties. Therefore by default, an auto sized track will take up any remaining space in the grid container. As the grid's inline size has to be less than the grid container's inline size for there to be space to distribute, the property has no effect in this case.

justify-content = 
  normal                                              |
  <content-distribution>                              |
  <overflow-position>? [ <content-position> | left | right ]  

<content-distribution> = 
  space-between  |
  space-around   |
  space-evenly   |
  stretch        

<overflow-position> = 
  unsafe  |
  safe    

<content-position> = 
  center      |
  start       |
  end         |
  flex-start  |
  flex-end    

In this example, we have a grid that is narrower than its grid container, and we use justify-content to distribute the available space evenly around and between the grid columns.

HTML

The <section> container, our grid container to-be, has 16 nested <div>s that will become grid items.

<section class="container">
  <div>A</div>
  <div>B</div>
  <div>C</div>
  <div>D</div>
  <div>E</div>
  <div>F</div>
  <div>G</div>
  <div>H</div>
  <div>I</div>
  <div>J</div>
  <div>K</div>
  <div>L</div>
  <div>M</div>
  <div>N</div>
  <div>O</div>
  <div>P</div>
</section>

CSS

.container {
  margin: 5px;
  border: 1px solid;
  box-sizing: border-box;
}

div {
  line-height: 2em;
  border: 1px solid;
  box-sizing: border-box;
  text-align: center;
}

We set the container width to 500px and specify three columns, each 80px wide, meaning there is 260px of available space to distribute between or around them. We then set justify-content: space-evenly, which means there will be 65px of space before, between, and after each column.

We set different widths (and background colors) to demonstrate how the justification is applied to the columns.

.container {
  display: grid;
  grid: auto-flow / repeat(3, 80px);
  width: 500px;
  justify-content: space-evenly;
}

div {
  background-color: pink;
  width: 80px;
}

div:nth-of-type(n + 9) {
  width: 35px;
  background-color: lightgreen;
}

div:nth-last-of-type(3) {
  width: 250px;
  background-color: lightblue;
}

Result

Note that justify-contents aligns the columns and has no effect on the items or alignment in grid areas. Grid items, even those that overflow their grid cell, do not impact column justification.

This example demonstrates the safe keyterm. We specify four centered flex items that are not allowed to wrap, and as a result, overflow their single flex-line container. By adding safe to center in the justify-content property, overflowing content behaves as if the alignment mode is start

<p><code>justify-content: center;</code></p>
<section class="container safe">
  <div>A</div>
  <div>B</div>
  <div>C</div>
  <div>D</div>
</section>
<p><code>justify-content: safe center;</code></p>
<section class="container safe-center">
  <div>A</div>
  <div>B</div>
  <div>C</div>
  <div>D</div>
</section>
<p><code>justify-content: safe center;</code> with 3 items</p>
<section class="container safe-center">
  <div>A</div>
  <div>B</div>
  <div>C</div>
</section>

.container {
  margin: 5px auto;
  border: 1px dashed;
  box-sizing: border-box;
  background-color: lightblue;
}

div {
  line-height: 1em;
  border: 1px solid;
  box-sizing: border-box;
  text-align: center;
  background-color: pink;
}

The container is set to center, with every container other than the first having the safe keyword added:

.container {
  align-items: baseline;
  display: flex;
  width: 350px;
  height: 2em;
}

.safe {
  justify-content: center;
}

.safe-center {
  justify-content: safe center;
}

div {
  flex: 0 0 100px;
}

Result

As an item overflows the alignment container, with safe included the alignment mode behaves as start and the center alignment is not implemented. The safe keyterm has no effect if the items do not overflow the container.

This example includes a multi-line wrapping flex layout. The second flex item has a positive flex growth factor, consuming all the available free space in the first flex line.

CSS

#container {
  margin: 5px auto;
  border: 1px dashed black;
  box-sizing: border-box;
}

div {
  line-height: 2em;
  border: 1px solid;
  box-sizing: border-box;
  text-align: center;
}

#container {
  display: flex;
  flex-flow: row wrap;
  justify-content: space-between; /* Can be changed in the live sample */
  width: 510px;
}

div {
  line-height: 2em;
  flex: 0 0 120px;
  background-color: pink;
}

div:nth-of-type(2) {
  flex-grow: 1;
  background-color: yellow;
}

div:nth-of-type(n + 9) {
  flex: 0 0 35px;
  background-color: lightgreen;
}
div:last-of-type {
  flex: 0 0 300px;
  background-color: lightblue;
}

<section id="container">
  <div>A</div>
  <div>GROW</div>
  <div>C</div>
  <div>D</div>
  <div>E</div>
  <div>F</div>
  <div>G</div>
  <div>H</div>
  <div>I</div>
  <div>J</div>
  <div>K</div>
  <div>L</div>
  <div>M</div>
  <div>N</div>
  <div>O</div>
  <div>P</div>
</section>
<select id="justifyContent">
  <option value="start">start</option>
  <option value="end">end</option>
  <option value="flex-start">flex-start</option>
  <option value="flex-end">flex-end</option>
  <option value="center">center</option>
  <option value="left">left</option>
  <option value="right">right</option>
  <option value="space-between" selected>space-between</option>
  <option value="space-around">space-around</option>
  <option value="space-evenly">space-evenly</option>
  <option value="stretch">stretch</option>
</select>

const justifyContent = document.getElementById("justifyContent");
justifyContent.addEventListener("change", (evt) => {
  document.getElementById("container").style.justifyContent = evt.target.value;
});

Result

Select different keywords from the drop-down menu to visualize the different justify-content keyword values. Because an item on the first line can grow, there is no available space on that line for the justify-content property to distribute. With the space-between value, the first item on each line is flush with the main-start edge, and the last item is flush with the main-end edge. As a result, if a line has only one item, it will be aligned with the main-start edge (as seen in the last line). This is not the case for other space-* values, such as space-evenly and space-around, which center one-item flex-lines.

• Basic concepts of flexbox
• Aligning items in a flex container
• Box alignment in CSS grid layouts
• CSS box alignment module