CSS Grid Layout implements the specification Box Alignment Level 3 which is the same standard flexbox uses for aligning items in its flex container. This specification details how alignment should work in all the different layout methods. Layout methods will conform to the specification where possible and implement individual behavior based on their differences (features and constraints). While the specification currently specifies alignment details for all layout methods, browsers have not fully implemented all of the specification; however, the CSS Grid Layout method has been widely adopted.
This guide presents demonstrations of how box alignment in grid layout works. You will see many similarities in how these properties and values work in flexbox. Due to grid being two-dimensional and flexbox one-dimensional there are some small differences that you should watch out for. So we will start by looking at the two axes that we deal with when aligning things in a grid.
When working with grid layout you have two axes available to align things against – the block axis 和 inline axis . The block axis is the axis upon which blocks are laid out in block layout. If you have two paragraphs on your page they display one below the other, so it is this direction we describe as the block axis.
inline axis runs across the block axis, it is the direction in which text in regular inline flow runs.
We are able to align the content inside grid areas, and the grid tracks themselves on these two axes.
align-self
and
align-items
properties control alignment on the block axis. When we use these properties, we are changing the alignment of the item within the grid area you have placed it.
In the following example, I have four grid areas within my grid. I can use the
align-items
property on the grid container, to align the items using one of the following values:
auto
normal
start
end
center
stretch
baseline
first baseline
last baseline
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(8, 1fr);
grid-gap: 10px;
grid-auto-rows: 100px;
grid-template-areas:
"a a a a b b b b"
"a a a a b b b b"
"c c c c d d d d"
"c c c c d d d d";
align-items: start;
}
.item1 {
grid-area: a;
}
.item2 {
grid-area: b;
}
.item3 {
grid-area: c;
}
.item4 {
grid-area: d;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
Keep in mind that once you set
align-items: start
, the height of each child
<div>
will be determined by the contents of the
<div>
. This is in contrast to omitting
align-items
completely, in which case the height of each
<div>
stretches to fill its grid area.
align-items
property sets the
align-self
property for all of the child grid items. This means that you can set the property individually, by using
align-self
on a grid item.
In this next example, I am using the
align-self
property, to demonstrate the different alignment values. The first area, is showing the default behavior of
align-self
, which is to stretch. The second item, has an
align-self
value of
start
, the third
end
and the fourth
center
.
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(8, 1fr);
grid-gap: 10px;
grid-auto-rows: 100px;
grid-template-areas:
"a a a a b b b b"
"a a a a b b b b"
"c c c c d d d d"
"c c c c d d d d";
}
.item1 {
grid-area: a;
}
.item2 {
grid-area: b;
align-self: start;
}
.item3 {
grid-area: c;
align-self: end;
}
.item4 {
grid-area: d;
align-self: center;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
The specification details that the default behavior in
align-self
is to stretch, except for items which have an intrinsic aspect ratio, in this case they behave as
start
. The reason for this, is that if items with an aspect ratio are set to stretch, this default would distort them.
This behavior has now been clarified in the specification, with browsers yet to implement the correct behavior. Until that happens, you can ensure that items do not stretch, such as images, which are direct children of the grid, by setting
align-self
and
justify-self
to start. This will mimic the correct behavior once implemented.
As
align-items
and
align-self
deal with the alignment of items on the block axis,
justify-items
and
justify-self
do the same job on the inline axis. The values you can choose from are the same as for
align-self
.
auto
normal
start
end
center
stretch
baseline
first baseline
last baseline
You can see the same example as used for
align-items
, below. This time we are applying the
justify-self
特性。
Once again the default is
stretch
, other than for items with an intrinsic aspect ratio. This means that by default, grid items will cover their grid area, unless you change that by setting alignment. The first item in the example demonstrates this default alignment:
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(8, 1fr);
grid-gap: 10px;
grid-auto-rows: 100px;
grid-template-areas:
"a a a a b b b b"
"a a a a b b b b"
"c c c c d d d d"
"c c c c d d d d";
}
.item1 {
grid-area: a;
}
.item2 {
grid-area: b;
justify-self: start;
}
.item3 {
grid-area: c;
justify-self: end;
}
.item4 {
grid-area: d;
justify-self: center;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
As with
align-self
and
align-items
, you can apply
justify-items
to the grid container, to set the
justify-self
value for all items.
justify-self
and
justify-items
properties are not implemented in flexbox. This is due to the one-dimensional nature of
flexbox
, and that there may be multiple items along the axis, making it impossible to justify a single item. To align items along the main, inline axis in flexbox you use the
justify-content
特性。
place-items
property is shorthand for
align-items
and
justify-items
.
place-self
property is shorthand for
align-self
and
justify-self
.
By combining the align and justify properties we can easily center an item inside a grid area.
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(4, 1fr);
grid-gap: 10px;
grid-auto-rows: 200px;
grid-template-areas:
". a a ."
". a a .";
}
.item1 {
grid-area: a;
align-self: center;
justify-self: center;
}
<div class="wrapper"> <div class="item1">Item 1</div> </div>
If you have a situation where your grid tracks use an area that is smaller than the grid container, then you can align the grid tracks themselves, inside that container. Once again, this operates on the block and inline axes, with
align-content
aligning tracks on the block axis, and
justify-content
performing alignment on the inline axis. The
place-content
property is shorthand for
align-content
and
justify-content
. The values for
align-content
,
justify-content
and
place-content
are:
normal
start
end
center
stretch
space-around
space-between
space-evenly
baseline
first baseline
last baseline
In the below example I have a grid container of 500 pixels by 500 pixels. I have defined 3 row and column tracks each of 100 pixels with a 10 pixel gutter. This means that there is space inside the grid container both in the block and inline directions.
align-content
property is applied to the grid container as it works on the entire grid. The default behavior in grid layout is
start
, which is why our grid tracks are in the top left corner of the grid, aligned against the start grid lines:
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(3, 100px);
grid-template-rows: repeat(3, 100px);
height: 500px;
width: 500px;
grid-gap: 10px;
grid-template-areas:
"a a b"
"a a b"
"c d d";
}
.item1 {
grid-area: a;
}
.item2 {
grid-area: b;
}
.item3 {
grid-area: c;
}
.item4 {
grid-area: d;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
If I add
align-content
to my container, with a value of
end
, the tracks all move to the end line of the grid container in the block dimension:
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(3, 100px);
grid-template-rows: repeat(3, 100px);
height: 500px;
width: 500px;
grid-gap: 10px;
grid-template-areas:
"a a b"
"a a b"
"c d d";
align-content: end;
}
.item1 {
grid-area: a;
}
.item2 {
grid-area: b;
}
.item3 {
grid-area: c;
}
.item4 {
grid-area: d;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
We can also use values for this property that you may be familiar with from flexbox; the space distribution values of
space-between
,
space-around
and
space-evenly
. If we update
align-content
to
space-between
, you can see how the elements on our grid space out:
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(3, 100px);
grid-template-rows: repeat(3, 100px);
height: 500px;
width: 500px;
grid-gap: 10px;
grid-template-areas:
"a a b"
"a a b"
"c d d";
align-content: space-between;
}
.item1 {
grid-area: a;
}
.item2 {
grid-area: b;
}
.item3 {
grid-area: c;
}
.item4 {
grid-area: d;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
It is worth noting, that using these space distribution values may cause items on your grid to become larger. If an item spans more than one grid track, as further space is added between the tracks, that item needs to become large to absorb the space. We’re always working in a strict grid. Therefore, if you decide to use these values, ensure that the content of your tracks can cope with the extra space, or that you have used alignment properties on the items, to cause them to move to the start rather than stretch.
In the below image I have placed the grid with
align-content
, with a value of
start
alongside the grid when
align-content
has a value of
space-between
. You can see how items 1 and 2, which span two row tracks have taken on extra height as they gain the additional space added to the gap between those two tracks:
On the inline axis, we can use
justify-content
to perform the same type of alignment that we used
align-content
for in the block axis.
Using the same example, I am setting
justify-content
to
space-around
. This once again causes tracks which span more than one column track to gain extra space:
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(3, 100px);
grid-template-rows: repeat(3, 100px);
height: 500px;
width: 500px;
grid-gap: 10px;
grid-template-areas:
"a a b"
"a a b"
"c d d";
align-content: space-between;
justify-content: space-around;
}
.item1 {
grid-area: a;
}
.item2 {
grid-area: b;
}
.item3 {
grid-area: c;
}
.item4 {
grid-area: d;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
Another way to align items inside their area, is to use auto margins. If you have ever centered your layout in the viewport, by setting the right and left margin of the container block to
auto
, you know that an auto margin absorbs all of the available space. By setting the margin to
auto
on both sides, it pushes the block into the middle as both margins attempt to take all of the space.
In this next example, I have given item 1 a left margin of
auto
. You can see how the content is now pushed over to the right side of the area, as the auto margin takes up remaining space, after room for the content of that item has been assigned:
* {box-sizing: border-box;}
.wrapper {
border: 2px solid #f76707;
border-radius: 5px;
background-color: #fff4e6;
}
.wrapper > div {
border: 2px solid #ffa94d;
border-radius: 5px;
background-color: #ffd8a8;
padding: 1em;
color: #d9480f;
}
.wrapper {
display: grid;
grid-template-columns: repeat(3, 100px);
grid-template-rows: repeat(3, 100px);
height: 500px;
width: 500px;
grid-gap: 10px;
grid-template-areas:
"a a b"
"a a b"
"c d d";
}
.item1 {
grid-area: a;
margin-left: auto;
}
.item2 {
grid-area: b;
}
.item3 {
grid-area: c;
}
.item4 {
grid-area: d;
}
<div class="wrapper"> <div class="item1">Item 1</div> <div class="item2">Item 2</div> <div class="item3">Item 3</div> <div class="item4">Item 4</div> </div>
You can see how the item is aligned by using the Firefox Grid Highlighter :
In all of these examples I have been working in English, which is a left-to-right language. This means that our start lines are top and left of our grid when thinking in physical directions.
CSS Grid Layout, and the Box Alignment specification are designed to work with writing modes in CSS. This means that if you are working in a right to left language, such as Arabic, the start of the grid would be the top and right, so the default of
justify-content: start
would be for grid tracks to start on the right hand side of the grid.
Setting auto margins, using
margin-right
or
margin-left
however, or absolutely positioning items using the
top
,
right
,
bottom
and
left
offsets would not honor writing modes. In the next guide, we will look further into this interaction between CSS grid layout, box alignment and writing modes. This will be important to understand, if you develop sites that are then displayed in multiple languages, or if you want to mix languages or writing modes in a design.