The grid-auto-columns CSS property specifies the size of an implicitly-created grid column track or pattern of tracks.

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If a grid item is positioned into a column that is not explicitly sized by grid-template-columns, implicit grid tracks are created to hold it. This can happen either by explicitly positioning into a column that is out of range, or by the auto-placement algorithm creating additional columns.


/* Keyword values */
grid-auto-columns: min-content;
grid-auto-columns: max-content;
grid-auto-columns: auto;

/* <length> values */
grid-auto-columns: 100px;
grid-auto-columns: 20cm;
grid-auto-columns: 50vmax;

/* <percentage> values */
grid-auto-columns: 10%;
grid-auto-columns: 33.3%;

/* <flex> values */
grid-auto-columns: 0.5fr;
grid-auto-columns: 3fr;

/* minmax() values */
grid-auto-columns: minmax(100px, auto);
grid-auto-columns: minmax(max-content, 2fr);
grid-auto-columns: minmax(20%, 80vmax);

/* fit-content() values */
grid-auto-columns: fit-content(400px);
grid-auto-columns: fit-content(5cm);
grid-auto-columns: fit-content(20%);

/* multiple track-size values */
grid-auto-columns: min-content max-content auto;
grid-auto-columns: 100px 150px 390px;
grid-auto-columns: 10% 33.3%;
grid-auto-columns: 0.5fr 3fr 1fr;
grid-auto-columns: minmax(100px, auto) minmax(max-content, 2fr) minmax(20%, 80vmax);
grid-auto-columns: 100px minmax(100px, auto) 10% 0.5fr fit-content(400px);

/* Global values */
grid-auto-columns: inherit;
grid-auto-columns: initial;
grid-auto-columns: revert;
grid-auto-columns: revert-layer;
grid-auto-columns: unset;



Is a non-negative length.


Is a non-negative <percentage> value relative to the block size of the grid container. If the block size of the grid container is indefinite, the percentage value is treated like auto.


Is a non-negative dimension with the unit fr specifying the track's flex factor. Each <flex>-sized track takes a share of the remaining space in proportion to its flex factor.

When appearing outside a minmax() notation, it implies an automatic minimum (i.e. minmax(auto, <flex>)).


Is a keyword representing the largest maximal content contribution of the grid items occupying the grid track.


Is a keyword representing the largest minimal content contribution of the grid items occupying the grid track.

minmax(min, max)

Is a functional notation that defines a size range greater than or equal to min and less than or equal to max. If max is smaller than min, then max is ignored and the function is treated as min. As a maximum, a <flex> value sets the track's flex factor. As a minimum, it is treated as zero (or minimal content, if the grid container is sized under a minimal content constraint).

fit-content( [ <length> | <percentage> ] )

Represents the formula min(max-content, max(auto, argument)), which is calculated similar to auto (i.e. minmax(auto, max-content)), except that the track size is clamped at argument if it is greater than the auto minimum.


As a maximum represents the largest max-content size of the items in that track.

As a minimum represents the largest minimum size of items in that track (specified by the min-width/min-height of the items). This is often, though not always, the min-content size.

If used outside of minmax() notation, auto represents the range between the minimum and maximum described above. This behaves similarly to minmax(min-content,max-content) in most cases.

Note: 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.

Formal definition

Initial value auto
Applies to grid containers
Inherited no
Percentages refer to corresponding dimension of the content area
Computed value the percentage as specified or the absolute length
Animation type discrete

Formal syntax

grid-auto-columns = 

<track-size> =
<track-breadth> |
minmax( <inflexible-breadth> , <track-breadth> ) |
fit-content( <length-percentage> )

<track-breadth> =
<length-percentage> |
<flex> |
min-content |
max-content |

<inflexible-breadth> =
<length-percentage> |
min-content |
max-content |

<length-percentage> =
<length> |


Setting grid column size


<div id="grid">
  <div id="item1"></div>
  <div id="item2"></div>
  <div id="item3"></div>


#grid {
  height: 100px;
  display: grid;
  grid-template-areas: "a a";
  gap: 10px;
  grid-auto-columns: 200px;

#grid > div {
  background-color: lime;



Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
grid-auto-columns 57 1612–79 70
52–70Does not accept multiple track-size values. See bug 1339672.
10 44 10.1 57 57 79
52–79Does not accept multiple track-size values. See bug 1339672.
43 10.3 6.0

See also

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