Make grid container fill columns not rows

I want my grid to fill in vertically like this:

1 4 7 
2 5 8
3 6 9
... arbitrary number of additional rows.

Instead, it fills in horizontally like this:

1 2 3
4 5 6
7 8 9

I want to specify the number of columns in my grid, not the number of rows.

This is what my div looks like with inline CSS styling:

<div style="display:grid; grid-template-columns:1fr 1fr 1fr;">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

It's important that my grid be 3 columns wide, but I want the items to be populated by column, not by row. Is this possible in CSS Grid? I've read through this https://css-tricks.com/snippets/css/complete-guide-grid/ but didn't see anything about order.

CSS Flexbox has flex-direction, isn't there an attribute like that for CSS Grid?

For a vertically-flowing grid that creates new columns as necessary, and rows are not defined, consider using CSS Multi-Column Layout (example). CSS Grid Layout (at least the current implementation - Level 1) cannot perform this task. Here's the problem:

In CSS Grid Layout, there is an inverse relationship between the grid-auto-flow and grid-template-rows / grid-template-columns properties.

More specifically, with grid-auto-flow: row (the default setting) and grid-template-columns both defined, grid items flow nicely in a horizontal direction, automatically creating new rows as necessary. This concept is illustrated in the code in the question.

#container {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  grid-auto-flow: row;
}

<div id="container">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

However, with a switch to grid-template-rows, grid items stack in a single column.

#container {
  display: grid;
  grid-template-rows: 1fr 1fr 1fr;
  grid-auto-flow: row;
}

<div id="container">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

There is no automatic creation of columns with grid-auto-flow: row and grid-template-rows. grid-template-columns must be defined (hence, the inverse relationship with grid-auto-flow).

#container {
  display: grid;
  grid-template-rows: 1fr 1fr 1fr;
  grid-template-columns: 1fr 1fr 1fr;
  grid-auto-flow: row;
}

<div id="container">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

The same behavior is true in the reverse scenario.

With grid-auto-flow: column and grid-template-rows both defined, grid items flow nicely in a vertical direction, automatically creating new columns as necessary.

#container {
  display: grid;
  grid-template-rows: 1fr 1fr 1fr;
  grid-auto-flow: column;
}

<div id="container">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

However, with a switch to grid-template-columns, grid items stack in a single row. (This is the problem most people ask about, including in this question.)

#container {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  grid-auto-flow: column;
}

<div id="container">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

There is no automatic creation of rows. That requires grid-template-rows to be defined. (This is the solution most often provided, but it is usually rejected because the layouts have a variable number of rows.)

#container {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  grid-template-rows: 1fr 1fr 1fr;
  grid-auto-flow: column;
}

<div id="container">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

Hence, consider a multi-column layout solution, as suggested above.

Spec reference: 7.7. Automatic Placement: the grid-auto-flow property

Another option is to drop CSS Grid and use CSS Columns, which does exactly what you ask and also have much better browser support.

.csscolumn {
  -webkit-column-count: 3;  /* Chrome, Safari, Opera */
  -moz-column-count: 3;     /* Firefox */
  column-count: 3;
}

/* styling for this demo */
.csscolumn {
  width: 50%;
}
.csscolumn + .csscolumn {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid;
}

<div class="csscolumn">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>

<div class="csscolumn">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
</div>

<div class="csscolumn">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
  <div>10</div>
</div>

More as a technical exercise than as a practical solution, you can get somehow your result using specific styles depending on the number of items

Let's see how it works:

.item:first-child:nth-last-child(n+4):nth-last-child(-n + 6) ~ .item:nth-child(n+3)

the first selector

.item:first-child:nth-last-child(n+4):nth-last-child(-n + 6)

is active is our list has between 4 and 6 elements. In this case, some item will be both in the first condition and in the second.

In this case, we want 2 items to be in the first column. target the remaining items (from the third onwards) with

~ .item:nth-child(n+3)

and put them on the second column. A similar rule, now for the 5th and onwards

~ .item:nth-child(n+5)

puts the other items in the third column. These 2 rules have the same precedence, and target both the last items, so it's critical that they appear in this order.

We need to repeat similar rules up to the maximum amount of items that can be present (probably a job for a preprocessor)

var elements = 5;

function add () {
    var ctn = document.getElementById("container");
    var ele = document.createElement("div");
    elements ++;
    ele.innerHTML = elements;
    ele.className = "item";
    ctn.appendChild (ele);
}

#container {
  width: 90%;
  border: solid 1px red;
  display: grid;
  grid-template-rows: 33% 33% 33%;
  grid-auto-flow: column dense;
}

.item {
  width: 90%;
  height: 80px;
  background-color: lightgreen;
  margin: 10px;
  grid-column: 1;
}

.item:first-child:nth-last-child(n+4):nth-last-child(-n + 6) ~ .item:nth-child(n+3) {
  background-color: yellow;
  grid-column: 2;
}

.item:first-child:nth-last-child(n+4):nth-last-child(-n + 6) ~ .item:nth-child(n+5) {
  background-color: tomato;
  grid-column: 3;
}

.item:first-child:nth-last-child(n+7):nth-last-child(-n + 9) ~ .item:nth-child(n+4) {
  background-color: burlywood;
  grid-column: 2;
}

.item:first-child:nth-last-child(n+7):nth-last-child(-n + 9) ~ .item:nth-child(n+7) {
  background-color: blueviolet;
  grid-column: 3;
}

.item:first-child:nth-last-child(n+10):nth-last-child(-n + 12) ~ .item:nth-child(n+5) {
  background-color: darkcyan;
  grid-column: 2;
}

.item:first-child:nth-last-child(n+10):nth-last-child(-n + 12) ~ .item:nth-child(n+9) {
  background-color: chartreuse;
  grid-column: 3;
}

.item:first-child:nth-last-child(n+13):nth-last-child(-n + 15) ~ .item:nth-child(n+6) {
  background-color: yellow;
  grid-column: 2;
}

.item:first-child:nth-last-child(n+13):nth-last-child(-n + 15) ~ .item:nth-child(n+11) {
  background-color: tomato;
  grid-column: 3;
}

<button onclick="add()">Add</button>
<div id="container">
<div class="item">1</div>
<div class="item">2</div>
<div class="item">3</div>
<div class="item">4</div>
<div class="item">5</div>
</div>

The simplest method I've seen follows:

.grid {
	display: grid;
	grid-auto-flow: column;
	grid-gap: 1px;
	grid-template-columns: repeat(3, 1fr); 
	grid-template-rows: repeat(5, auto);    
}

<div class="grid">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
<div>5</div>
<div>6</div>
<div>7</div>
<div>8</div>
<div>9</div>
<div>10</div>
<div>11</div>
<div>12</div>
<div>13</div>
</div>

Here is one CSS Grid based approach using javascript and the CSSOM to insert a pair of:

transform: translate(x, y)

rules into a generated stylesheet.

The two transform rules (there are only two, based on the grid being 3 columns wide displace the lower elements of the original single column grid, moving the elements upwards and to the right.

Consequently, you can add any number of elements to the single-column grid, and the script will always adjust the grid so that it has three columns of more or less equal size.

If the columns cannot be of exactly equal size, then the taller column(s) will always be the first and / or second column (never the rightmost, third column).

Working Example (9 grid units):

var numberOfColumns = 3;

document.head.appendChild(document.createElement('style'));
var newStyles = document.styleSheets[(document.styleSheets.length - 1)];

var myGrid = document.getElementsByClassName('my-grid')[0];
var myGridUnits = myGrid.getElementsByTagName('div');

var tallColumn = Math.ceil(myGridUnits.length /  numberOfColumns);
var shortColumn = Math.floor(myGridUnits.length / numberOfColumns);

var nextUnit = 1;
var unitsRemaining = myGridUnits.length;
var xTranslate, yTranslate;
var columns = [];

for (var i = 0; i < (numberOfColumns - 1); i++) {


    if (unitsRemaining % shortColumn === 0) {
    
        columns.push(shortColumn);
    }

    else {

        columns.push(tallColumn);
    }
    
    nextUnit += columns[(columns.length - 1)];
    unitsRemaining -= columns[(columns.length - 1)];
    
    xTranslate = ((i + 1) * 48);
    yTranslate = 0;
    columns.forEach(function(columnHeight){yTranslate += (columnHeight * 48);});
                         
    newStyles.insertRule('.my-grid div:nth-of-type(n+' + nextUnit + ') {transform: translate(' + xTranslate + 'px, ' + (0 - (yTranslate)) + 'px);}', newStyles.cssRules.length);

}

.my-grid {
display: inline-grid;
grid-row-gap: 6px;
}

.my-grid div {
width: 40px;
height: 40px;
line-height: 40px;
text-align: center;
border: 1px solid rgb(127, 127, 127);
}

<div class="my-grid">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
<div>5</div>
<div>6</div>
<div>7</div>
<div>8</div>
<div>9</div>
</div>

---

Working Example (10 grid units):

var numberOfColumns = 3;

document.head.appendChild(document.createElement('style'));

var newStyles = document.styleSheets[(document.styleSheets.length - 1)];

var myGrid = document.getElementsByClassName('my-grid')[0];
var myGridUnits = myGrid.getElementsByTagName('div');

var tallColumn = Math.ceil(myGridUnits.length /  numberOfColumns);
var shortColumn = Math.floor(myGridUnits.length / numberOfColumns);

var nextUnit = 1;
var unitsRemaining = myGridUnits.length;
var xTranslate, yTranslate;
var columns = [];

for (var i = 0; i < (numberOfColumns - 1); i++) {


    if (unitsRemaining % shortColumn === 0) {
    
        columns.push(shortColumn);
    }

    else {

        columns.push(tallColumn);
    }
    
    nextUnit += columns[(columns.length - 1)];
    unitsRemaining -= columns[(columns.length - 1)];
    
    xTranslate = ((i + 1) * 48);
    yTranslate = 0;
    columns.forEach(function(columnHeight){yTranslate += (columnHeight * 48);});
                         
    newStyles.insertRule('.my-grid div:nth-of-type(n+' + nextUnit + ') {transform: translate(' + xTranslate + 'px, ' + (0 - (yTranslate)) + 'px);}', newStyles.cssRules.length);

}

.my-grid {
display: inline-grid;
grid-row-gap: 6px;
}

.my-grid div {
width: 40px;
height: 40px;
line-height: 40px;
text-align: center;
border: 1px solid rgb(127, 127, 127);
}

<div class="my-grid">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
<div>5</div>
<div>6</div>
<div>7</div>
<div>8</div>
<div>9</div>
<div>10</div>
</div>

---

Working Example (11 grid units):

var numberOfColumns = 3;

document.head.appendChild(document.createElement('style'));

var newStyles = document.styleSheets[(document.styleSheets.length - 1)];

var myGrid = document.getElementsByClassName('my-grid')[0];
var myGridUnits = myGrid.getElementsByTagName('div');

var tallColumn = Math.ceil(myGridUnits.length /  numberOfColumns);
var shortColumn = Math.floor(myGridUnits.length / numberOfColumns);

var nextUnit = 1;
var unitsRemaining = myGridUnits.length;
var xTranslate, yTranslate;
var columns = [];

for (var i = 0; i < (numberOfColumns - 1); i++) {


    if (unitsRemaining % shortColumn === 0) {
    
        columns.push(shortColumn);
    }

    else {

        columns.push(tallColumn);
    }
    
    nextUnit += columns[(columns.length - 1)];
    unitsRemaining -= columns[(columns.length - 1)];
    
    xTranslate = ((i + 1) * 48);
    yTranslate = 0;
    columns.forEach(function(columnHeight){yTranslate += (columnHeight * 48);});
                         
    newStyles.insertRule('.my-grid div:nth-of-type(n+' + nextUnit + ') {transform: translate(' + xTranslate + 'px, ' + (0 - (yTranslate)) + 'px);}', newStyles.cssRules.length);

}

.my-grid {
display: inline-grid;
grid-row-gap: 6px;
}

.my-grid div {
width: 40px;
height: 40px;
line-height: 40px;
text-align: center;
border: 1px solid rgb(127, 127, 127);
}

<div class="my-grid">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
<div>5</div>
<div>6</div>
<div>7</div>
<div>8</div>
<div>9</div>
<div>10</div>
<div>11</div>
</div>

Working Example (14 grid units):

var numberOfColumns = 3;

document.head.appendChild(document.createElement('style'));

var newStyles = document.styleSheets[(document.styleSheets.length - 1)];

var myGrid = document.getElementsByClassName('my-grid')[0];
var myGridUnits = myGrid.getElementsByTagName('div');

var tallColumn = Math.ceil(myGridUnits.length /  numberOfColumns);
var shortColumn = Math.floor(myGridUnits.length / numberOfColumns);

var nextUnit = 1;
var unitsRemaining = myGridUnits.length;
var xTranslate, yTranslate;
var columns = [];

for (var i = 0; i < (numberOfColumns - 1); i++) {


    if (unitsRemaining % shortColumn === 0) {
    
        columns.push(shortColumn);
    }

    else {

        columns.push(tallColumn);
    }
    
    nextUnit += columns[(columns.length - 1)];
    unitsRemaining -= columns[(columns.length - 1)];
    
    xTranslate = ((i + 1) * 48);
    yTranslate = 0;
    columns.forEach(function(columnHeight){yTranslate += (columnHeight * 48);});
                         
    newStyles.insertRule('.my-grid div:nth-of-type(n+' + nextUnit + ') {transform: translate(' + xTranslate + 'px, ' + (0 - (yTranslate)) + 'px);}', newStyles.cssRules.length);

}

.my-grid {
display: inline-grid;
grid-row-gap: 6px;
}

.my-grid div {
width: 40px;
height: 40px;
line-height: 40px;
text-align: center;
border: 1px solid rgb(127, 127, 127);
}

<div class="my-grid">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
<div>5</div>
<div>6</div>
<div>7</div>
<div>8</div>
<div>9</div>
<div>10</div>
<div>11</div>
<div>12</div>
<div>13</div>
<div>14</div>
</div>