CSS Grid Layout Module Level 1

Editor’s Draft, 29 August 2014

This version:
http://dev.w3.org/csswg/css-grid/
Latest version:
http://www.w3.org/TR/css-grid-1/
Previous Versions:
http://www.w3.org/TR/2014/WD-css-grid-1-20140513/
http://www.w3.org/TR/2014/WD-css-grid-1-20140123/
http://www.w3.org/TR/2013/WD-css3-grid-layout-20130402/
http://www.w3.org/TR/2012/WD-css3-grid-layout-20121106/
Feedback:
www-style@w3.org with subject line “[css-grid] … message topic …”(archives)
Editors:
fantasai (Mozilla)
(Microsoft)
Former Editors:
(Microsoft Corporation)
(Microsoft Corporation)
Issues list:
In Bugzilla

Abstract

This CSS module defines a two-dimensional grid-based layout system, optimized for user interface design. In the grid layout model, the children of a grid container can be positioned into arbitrary slots in a flexible or fixed predefined layout grid.

CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, in speech, etc.

Status of this document

This is a public copy of the editors’ draft. It is provided for discussion only and may change at any moment. Its publication here does not imply endorsement of its contents by W3C. Don’t cite this document other than as work in progress.

The (archived) public mailing list www-style@w3.org (see instructions) is preferred for discussion of this specification. When sending e-mail, please put the text “css-grid” in the subject, preferably like this: “[css-grid] …summary of comment…

This document was produced by the CSS Working Group (part of the Style Activity).

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

The following features are at-risk, and may be dropped during the CR period:

Table of Contents

1 Introduction and Overview

Grid layout contains features targeted at web application authors. The grid can be used to achieve many different layouts. It excels at dividing up space for major regions of an application, or defining the relationship in terms of size, position, and layer between parts of a control built from HTML primitives.

Like tables, grid layout enables an author to align elements into columns and rows, but unlike tables, grid layout doesn’t have content structure, and thus enables a wide variety of layouts not possible with tables. For example, the children of a grid container can position themselves such that they overlap and layer similar to positioned elements.

In addition, the absence of content structure in grid layout helps to manage changes to layout by using fluid and source order independent layout techniques. By combining media queries with the CSS properties that control layout of the grid container and its children, authors can adapt their layout to changes in device form factors, orientation, and available space, without needing to alter the semantic nature of their content.

1.1 Background and Motivation

Image: Application layout example requiring horizontal and vertical alignment.
Application layout example requiring horizontal and vertical alignment.

As websites evolved from simple documents into complex, interactive applications, tools for document layout, e.g. floats, were not necessarily well suited for application layout. By using a combination of tables, JavaScript, or careful measurements on floated elements, authors discovered workarounds to achieve desired layouts. Layouts that adapted to the available space were often brittle and resulted in counter-intuitive behavior as space became constrained. As an alternative, authors of many web applications opted for a fixed layout that cannot take advantage of changes in the available rendering space on a screen.

The capabilities of grid layout address these problems. It provides a mechanism for authors to divide available space for layout into columns and rows using a set of predictable sizing behaviors. Authors can then precisely position and size the building block elements of their application by into grid areas defined by these columns and rows. Figure 1 illustrates a basic layout which can be achieved with grid layout.

1.2 Adapting Layouts to Available Space

Image: Five grid items arranged according to content size and available space.
Five grid items arranged according to content size and available space.
Image: Growth in the grid due to an increase in available space.
Growth in the grid due to an increase in available space.

Grid layout can be used to intelligently reflow elements within a webpage. Figure 2 represents a game with five major areas in the layout: the game title, stats area, game board, score area, and control area. The author’s intent is to divide the space for the game such that:

As an alternative to using script to control the absolute position, width, and height of all elements, the author can use grid layout, as shown in Figure 3. The following example shows how an author might achieve all the sizing, placement, and alignment rules declaratively.

Note that there are multiple ways to specify the structure of the grid and to position and size grid items, each optimized for different scenarios. This example illustrates one that an author may use to define the position and space for each grid item using the grid-template-rows and grid-template-columns properties on the grid container, and the grid-row and grid-column properties on each grid item.

<style type="text/css">
  #grid {
  display: grid;
  /* Two columns: the first sized to content, the second receives
   * the remaining space, but is never smaller than the minimum
   * size of the board or the game controls, which occupy this
   * column. */
  grid-template-columns: auto minmax(min-content, 1fr);
  /* Three rows: the first and last sized to content, the middle
   * row receives the remaining space, but is never smaller than
   * the minimum height of the board or stats areas. */
  grid-template-rows: auto minmax(min-content, 1fr) auto
  }
  /* Each part of the game is positioned between grid lines by
   * referencing the starting grid line and then specifying, if more
   * than one, the number of rows or columns spanned to determine
   * the ending grid line, which establishes bounds for the part. */
  #title    { grid-column: 1; grid-row: 1 }
  #score    { grid-column: 1; grid-row: 3 }
  #stats    { grid-column: 1; grid-row: 2; justify-self: start }
  #board    { grid-column: 2; grid-row: 1 / span 2; }
  #controls { grid-column: 2; grid-row: 3; align-self: center }
</style>
<div id="grid">
  <div id="title">Game Title</div>
  <div id="score">Score</div>
  <div id="stats">Stats</div>
  <div id="board">Board</div>
  <div id="controls">Controls</div>
</div>

1.3 Source Independence

Image: An arrangement suitable for portrait orientation.
An arrangement suitable for portrait orientation.
Image: An arrangement suitable for landscape orientation.
An arrangement suitable for landscape orientation.

Continuing the prior example, the author also wants the game to adapt to the space available on traditional computer monitors, handheld devices, or tablet computers. Also, the game should optimize the placement of the components when viewed either in landscape or portrait orientation (Figures 4 and 5). By combining grid layout with media queries, the author is able to use the same semantic markup, but rearrange the layout of elements independent of their source order, to achieve the desired layout in both orientations.

The following example leverages grid layout’s ability to name the space which will be occupied by a grid item. This allows the author to avoid rewriting rules for grid items as the grid’s definition changes.

<style type="text/css">
  @media (orientation: portrait) {
  #grid {
    display: grid;
    /* The rows, columns and areas of the grid are defined visually
     * using the grid-template-areas property.  Each string is a row, and
     * each word an area.  The number of words in a string
     * determines the number of columns. Note the number of words
     * in each string must be identical. */
    grid-template-areas: "title stats"
               "score stats"
               "board board"
               "ctrls ctrls";
    /* Columns and rows created with the template property can be
     * assigned a sizing function with the grid-template-columns
     * and grid-template-rows properties. */
    grid-template-columns: auto minmax(min-content, 1fr);
    grid-template-rows: auto auto minmax(min-content, 1fr) auto
  }
  }
  @media (orientation: landscape) {
  #grid {
    display: grid;
    /* Again the template property defines areas of the same name,
     * but this time positioned differently to better suit a
     * landscape orientation. */
    grid-template-areas: "title board"
               "stats board"
               "score ctrls";
    grid-template-columns: auto minmax(min-content, 1fr);
    grid-template-rows: auto minmax(min-content, 1fr) auto
  }
  }
  /* The grid-area property places a grid item into a named
   * region (area) of the grid. */
  #title    { grid-area: title }
  #score    { grid-area: score }
  #stats    { grid-area: stats }
  #board    { grid-area: board }
  #controls { grid-area: ctrls }
</style>
<div id="grid">
  <div id="title">Game Title</div>
  <div id="score">Score</div>
  <div id="stats">Stats</div>
  <div id="board">Board</div>
  <div id="controls">Controls</div>
</div>

1.4 Grid Layering of Elements

Image: A control composed of layered HTML elements.
A control composed of layered HTML elements.

In the example shown in Figure 6, the author is creating a custom slider control. The control has six parts. The lower and upper labels align to the left and right edges of the control. The track of the slider spans the area between the labels. The lower and upper fill parts touch beneath the thumb, and the thumb is a fixed width and height that can be moved along the track by updating the two flex-sized columns.

Prior to the introduction of grid layout, the author would have likely used absolute positioning to control the top and left coordinates, along with the width and height of each HTML element that comprises the control. By leveraging grid layout, the author can instead limit script usage to handling mouse events on the thumb, which snaps to various positions along the track as the grid-template-columns property of the grid container is updated.

<style type="text/css">
  #grid {
  display: grid;
  /* The grid-template-columns and rows properties also support
   * naming grid lines which can then be used to position grid
   * items.  The line names are assigned on either side of a column
   * or row sizing function where the line would logically exist. */
  grid-template-columns:
    (start)        auto
    (track-start)  0.5fr
    (thumb-start)  auto
    (fill-split)   auto
    (thumb-end)    0.5fr
    (track-end)    auto
    (end);
  }
  /* The grid-placement properties accept named lines. Below the
   * lines are referred to by name. Beyond any
   * semantic advantage, the names also allow the author to avoid
   * renumbering the grid-column-start and grid-row-start properties of the
   * grid items.  This is similar to the concept demonstrated in the
   * prior example with the grid-template-areas property during orientation
   * changes, but grid lines can also work with layered grid items
   * that have overlapping areas of different shapes like the thumb
   * and track parts  in this example. */
  #lower-label { grid-column-start: start }
  #track       { grid-column: track-start / track-end; align-self: center }
  #upper-label { grid-column-end: end; }
  /* Fill parts are drawn above the track so set z-index to 5. */
  #lower-fill  { grid-column: track-start / fill-split;
         align-self: end;
         z-index: 5 }
  #upper-fill  { grid-column: fill-split / track-end;
         align-self: start;
         z-index: 5 }
  /* Thumb is the topmost part; assign it the highest z-index value. */
  #thumb       { grid-column: thumb-start / thumb-end; z-index: 10 }
</style>
<div id="grid">
  <div id="lower-label">Lower Label</div>
  <div id="upper-label">Upper Label</div>
  <div id="track">Track</div>
  <div id="lower-fill">Lower Fill</div>
  <div id="upper-fill">Upper Fill</div>
  <div id="thumb">Thumb</div>
</div>

2 Grid Layout Concepts and Terminology

In grid layout, the content of a grid container is laid out by positioning and aligning it into a grid. The grid is an intersecting set of horizontal and vertical grid lines that divides the grid container’s space into grid areas, into which grid items (representing the grid container’s content) can be placed. There are two sets of grid lines: one set defining columns that run along the block axis (the column axis), and an orthogonal set defining rows along the inline axis (the row axis). [CSS3-WRITING-MODES]

Image: Grid Lines.
Grid lines: Three in the block axis and four in the inline axis.

2.1 Grid Tracks and Cells

Grid track is a generic term for a grid column or grid row—in other words, it is the space between two adjacent grid lines. Each grid track is assigned a sizing function, which controls how wide or tall the column or row may grow, and thus how far apart its bounding grid lines are.

A grid cell is the similar term for the full grid—it is the space between two adjacent row and two adjacent column grid lines. It is the smallest unit of the grid that can be referenced when positioning grid items.

In the following example there are two columns and three rows. The first column is fixed at 150px. The second column uses flexible sizing, which is a function of the unassigned space in the Grid, and thus will vary as the width of the grid container changes. If the used width of the grid container is 200px, then the second column 50px wide. If the used width of the grid container is 100px, then the second column is 0px and any content positioned in the column will overflow the grid container.
<style type="text/css">
  #grid {
    display: grid;
    grid-template-columns: 150px 1fr; /* two columns */
    grid-template-rows: 50px 1fr 50px /* three rows  */
  }
</style>

2.2 Grid Lines

Grid lines are the horizontal and vertical dividing lines of the grid. A grid line exists on either side of a column or row. They can be referred to by numerical index, or by an author-specified name. A grid item references the grid lines to determine its position within the grid using the grid-placement properties.

The following two examples create three column grid lines and four row grid lines. The first example demonstrates how an author would position a grid item using grid line numbers. The second example uses explicitly named grid lines.
<style type="text/css">
  #grid {
  display: grid;
  grid-template-columns: 150px 1fr;
  grid-template-rows: 50px 1fr 50px
  }
  #item1 { grid-column: 2;
       grid-row-start: 1; grid-row-end: 4; }
</style>
<style type="text/css">
  /* equivalent layout to the prior example, but using named lines */
  #grid {
  display: grid;
  grid-template-columns: 150px (item1-start) 1fr (item1-end);
  grid-template-rows: (item1-start) 50px 1fr 50px (item1-end);
  }
  #item1 {
  grid-column: item1-start / item1-end;
  grid-row: item1-start / item1-end
  }
</style>

2.3 Grid Areas

A grid area is the logical space used to lay out one or more grid items. It is bound by four grid lines, one on each side of the grid area, and participates in the sizing of the grid tracks it intersects. A grid area can be named explicitly using the grid-template-areas property of the grid container, or referenced implicitly by its bounding grid lines. A grid item is assigned to a grid area using the grid-placement properties.

<style type="text/css">
  /* using the template syntax */
  #grid  {
  display: grid;
  grid-template-areas: ". a"
             "b a"
             ". a";
  grid-template-columns: 150px 1fr;
  grid-template-rows: 50px 1fr 50px
  }
  #item1 { grid-area: a }
  #item2 { grid-area: b }
  #item3 { grid-area: b }
  /* Align items 2 and 3 at different points in the Grid Area "b".  */
  /* By default, Grid Items are stretched to fit their Grid Area    */
  /* and these items would layer one over the other. */
  #item2 { align-self: start }
  #item3 { justify-self: end; align-self: end }
</style>

A grid item’s grid area forms the containing block into which it is laid out. Percentage lengths specified on a grid item resolve against this containing block. Percentages specified for margin-top, padding-top, margin-bottom, and padding-bottom on a grid item resolve against the height of its containing block, rather than the width (as for blocks).

Grid items placed into the same grid area do not directly affect each other’s layout. Indirectly, a grid item can affect the position of a grid line in a column or row that uses a contents-based relative size, which in turn can affect the position or size of another grid item.

3 Grid Containers

3.1 Establishing Grid Containers: the grid and inline-grid display values

Name:display
New values:grid | inline-grid
grid
This value causes an element to generate a block-level grid container box.
inline-grid
This value causes an element to generate an inline-level grid container box.

A grid container establishes a new grid formatting context for its contents. This is the same as establishing a block formatting context, except that grid layout is used instead of block layout: floats do not intrude into the grid container, and the grid container’s margins do not collapse with the margins of its contents. Grid containers form a containing block for their contents exactly like block containers do. [CSS21] The overflow property applies to grid containers.

Grid containers are not block containers, and so some properties that were designed with the assumption of block layout don’t apply in the context of grid layout. In particular:

If an element’s specified display is inline-grid and the element is floated or absolutely positioned, the computed value of display is grid. The table in CSS 2.1 Chapter 9.7 is thus amended to contain an additional row, with inline-grid in the "Specified Value" column and grid in the "Computed Value" column.

3.2 Sizing Grid Containers

A grid container is sized using the rules of the formatting context in which it participates. As a block-level box in a block formatting context, it is sized like any other block-level box that establishes a formatting context, with an auto inline size calculated as for in-flow block boxes. As an inline-level box in an inline formatting context, it is sized as an atomic inline-level box (such as an inline-block). In both inline and block formatting contexts, the grid container’s auto block size is its max-content size. The block layout spec should define this?

The max-content size of a grid container is the sum of the grid container’s track sizes in the appropriate axis, when the grid is sized under a max-content constraint.

The min-content size of a grid container is the sum of the grid container’s track sizes in the appropriate axis, when the grid is sized under a min-content constraint.

See [CSS3-SIZING] for a definition of the terms in this section.

4 Grid Items

The contents of a grid container consists of zero or more grid items: each child of a grid container becomes a grid item, and each contiguous run of text that is directly contained inside a grid container is wrapped in an anonymous grid item. However, an anonymous grid item that contains only white space is not rendered, as if it were display:none.

A grid item establishes a new formatting context for its contents. The type of this formatting context is determined by its display value, as usual. The computed display of a grid item is determined by applying the table in CSS 2.1 Chapter 9.7. However, grid items are grid-level boxes, not block-level boxes: they participate in their container’s grid formatting context, not in a block formatting context.

Examples of grid items:
<div style="display:grid">

  <!-- grid item: block child -->
  <div id="item1">block</div>

  <!-- grid item: floated element; floating is ignored -->
  <div id="item2" style="float: left;">float</div>

  <!-- grid item: anonymous block box around inline content -->
  anonymous item 3

  <!-- grid item: inline child -->
  <span>
    item 4
    <!-- grid items do not split around blocks -->
    <div id=not-an-item>item 4</div>
    item 4
  </span>
</div>

Some values of display trigger the generation of anonymous boxes. For example, a misparented table-cell child is fixed up by generating anonymous table and table-row elements around it. [CSS21] This fixup must occur before a grid container’s children are promoted to grid items. For example, given two contiguous child elements with display:table-cell, an anonymous table wrapper box around them becomes the grid item.

Future display types may generate anonymous containers (e.g. ruby) or otherwise mangle the box tree (e.g. run-ins). It is intended that grid item determination run after these operations.

4.1 Collapsed Grid Items: the visibility property

We want the ability to collapse grid tracks (similar to collapsing flex items or table rows/columns), but we’re not sure exactly how to do it. Ideas welcome, please post them to www-style@w3.org.

4.2 Reordered Grid Items: the order property

The order property also applies to grid items. It affects their auto-placement and painting order.

4.3 Static Position of Grid Container Children

The static position [CSS21] of an absolutely-positioned child of a grid container is determined as if it were the sole grid item in a fixed-size grid area whose edges coincide with the padding edges of the grid container.

Note: Note that this position is affected by the values of justify-self and align-self on the child, and that, as in most other layout models, the absolutely-positioned child has no effect on the size of the containing block or layout of its contents.

5 The Explicit Grid

The three properties grid-template-rows, grid-template-columns, and grid-template-areas together define the explicit grid of a grid container. The grid-template property is a shorthand that sets all three at the same time. The final grid may end up larger due to grid items placed outside the explicit grid; in this case, any implicit tracks are sized by the grid-auto-rows and grid-auto-columns properties.

The size of the explicit grid is determined by the larger of the number of rows/columns defined by grid-template-areas and the number of rows/columns sized by grid-template-rows/grid-template-columns. Any rows/columns defined by grid-template-areas but not sized by grid-template-rows/grid-template-columns take their size from the grid-auto-rows/grid-auto-columns properties.

Numeric indexes in the grid-placement properties count from the edges of the explicit grid, starting from 1. Positive indexes count from the before/start side, while negative indexes count from the after/end side.

Implementations may limit the possible size of the explicit grid. If they do, attempting to specify an explicit grid larger than the implementation-defined maximum must instead define an explicit grid of the maximum size. Implementations may cap the explicit grid to slightly less than the maximum, in order to have only whole repetitions of the repeat() function. It is recommended that the maximum size of the explicit grid not be smaller than 1 million tracks in each axis.

5.1 Track Sizing: the grid-template-rows and grid-template-columns properties

Name:grid-template-columns, grid-template-rows
Value:none | <track-list> | subgrid <line-name-list>?
Initial:none
Applies to:grid containers
Inherited:no
Media:visual
Computed value:As specified, except for auto (see prose), with lengths made absolute
Percentages:refer to corresponding dimension of the content area

These properties specify, as a space-separated track list, the line names and track sizing functions of the grid. Each track sizing function can be specified as a length, a percentage of the grid container’s size, a measurement of the contents occupying the column or row, or a fraction of the free space in the grid. It can also be specified as a range using the minmax() notation, which can combine any of the previously mentioned mechanisms to specify separate min and max track sizing functions for the column or row.

The grid-template-columns property specifies the track list for the grid’s columns, while grid-template-rows specifies the track list for the grid’s rows. The syntax of a track list is:

<track-list>     = [ <line-names>? [ <track-size> | <repeat()> ] ]+ <line-names>?
<track-size>     = minmax( <track-breadth> , <track-breadth> ) | auto | <track-breadth>
<track-breadth>  = <length> | <percentage> | <flex> | min-content | max-content
<line-names>     = ( <custom-ident>* )
<line-name-list> = [ <line-names> | repeat(<positive-integer>, <line-names>+) ]+

Where:

<length>
A non-negative length, as defined by CSS3 Values. [CSS3VAL]
<percentage>
A non-negative percentage, as defined by CSS3 Values. [CSS3VAL] <percentage> values are relative to the inline size of the grid container in column grid tracks, and the block size of the grid container in row grid tracks. If the inline or block size of the grid container is indefinite, <percentage> values relative to that size are treated as auto (or, if in a minmax() function, as min-content when in the first position and as max-content when in the second).
<flex>
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. See Flexible Lengths for more details.
max-content
Represents the largest max-content contribution of the grid items occupying the grid track.
min-content
Represents the largest min-content contribution of the grid items occupying the grid track.
minmax(min, max)
Defines a size range greater than or equal to min and less than or equal to max. If max < min, then max is ignored and minmax(min,max) 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 min-content, if the grid container is sized under a min-content constraint).
auto
Computes to minmax(min-content, max-content).

The none value indicates that there is no explicit grid; any rows/columns will be implicitly generated, and their size will be determined by the grid-auto-rows and grid-auto-columns properties.

The subgrid value indicates that the grid will align to its parent grid in that axis. Rather than specifying the sizes of rows/columns explicitly, they’ll be taken from the parent grid’s definition.

Given the following grid-template-columns declaration:
grid-template-columns: 100px 1fr max-content minmax(min-content, 1fr);

Five grid lines are created:

  1. At the start edge of the grid container.
  2. 100px from the start edge of the grid container.
  3. A distance from the previous line equal to half the free space (the width of the grid container, minus the width of the non-flexible grid tracks).
  4. A distance from the previous line equal to the maximum size of any grid items belonging to the column between these two lines.
  5. A distance from the previous line at least as large as the largest minimum size of any grid items belonging to the column between these two lines, but no larger than the other half of the free space.

If the non-flexible sizes (100px, max-content, and min-content) sum to larger than the grid container’s width, the final grid line will be a distance equal to their sum away from the start edge of the grid container (the 1fr sizes both resolve to 0). If the sum is less than the grid container’s width, the final grid line will be exactly at the end edge of the grid container. This is true in general whenever there’s at least one <flex> value among the grid track sizes.

Additional examples of valid grid track definitions:
/* examples of valid track definitions */
grid-template-rows: 1fr minmax(min-content, 1fr);
grid-template-rows: 10px repeat(2, 1fr auto minmax(30%, 1fr));
grid-template-rows: calc(4em - 5px)

5.1.1 Named Grid Lines: the ''(<custom-ident>*)'' syntax

While grid lines can always be referred to by their numerical index, named lines can make the grid-placement properties easier to understand and maintain. Lines can be explicitly named in the grid-template-rows and grid-template-columns properties, or implicitly named by creating named grid areas with the grid-template-areas property.

For example, the following code gives meaningful names to all of the lines in the grid. Note that some of the lines have multiple names.
<style>
  #grid {
  display: grid;
  grid-template-columns: (first nav) 150px (main) 1fr (last);
  grid-template-rows: (first header) 50px (main) 1fr (footer) 50px (last);
  }
</style>
Image: Named Grid Lines.
Named Grid Lines.

5.1.2 Repeating Rows and Columns: the repeat() notation

The repeat() notation represents a repeated fragment of the track list. This is just a syntactic shorthand that allows writing a large number of columns or rows that exhibit a recurring pattern in a more compact form. The syntax of the repeat() notation is:

repeat() = repeat( <positive-integer> , [ <line-names>? <track-size> ]+ <line-names>? )

The first argument specifies the number of repetitions. The second argument is a track list, which is repeated that number of times. The repeat() notation cannot be nested; doing so makes the declaration invalid.

This example shows two equivalent ways of writing the same grid definition. Both ways produce a grid with a single row and four "main" columns, each 250px wide, surrounded by 10px "gutter" columns.
<style>
  #grid {
  display: grid;
  grid-template-columns: 10px (col-start) 250px (col-end)
               10px (col-start) 250px (col-end)
               10px (col-start) 250px (col-end)
               10px (col-start) 250px (col-end) 10px;
  grid-template-rows: 1fr;
  }
  /* Equivalent definition. */
  #grid {
  display: grid;
  grid-template-columns: repeat(4, 10px (col-start) 250px (col-end)) 10px;
  grid-template-rows: 1fr;
  }
</style>

If the repeat() function ends up placing two <line-names> adjacent to each other, the name lists are merged. For example, repeat(2, (a) 1fr (b)) is equivalent to (a) 1fr (b a) 1fr (b).

Note: It is expected that a future level of this specification will define a value to be inserted between the repetitions, similar to the argument of the Array#join method in JavaScript.

5.1.3 Flexible Lengths: the fr unit

A flexible length or <flex> is a dimension with the fr unit, which represents a fraction of the free space in the grid container.

The distribution of free space occurs after all non-flexible track sizing functions have reached their maximum. The total size of such rows or columns is subtracted from the available space, yielding the free space, which is then divided among the flex-sized rows and columns in proportion to their flex factor.

Note: Flexible lengths in a track list work similarly to flexible lengths with a zero base size in [CSS3-FLEXBOX].

Each column or row’s share of the free space can be computed as the column or row’s <flex> * <free space> / <sum of all flex factors. For the purpose of this calculation, a flexible length in the min position of a minmax() function is treated as 0 (an inflexible length).

When the available space is infinite (which happens when the grid container’s width or height is indefinite), flex-sized grid tracks are sized to their contents while retaining their respective proportions. The used size of each flex-sized grid track is computed by determining the max-content size of each flex-sized grid track and dividing that size by the respective flex factor to determine a “hypothetical 1fr size”. The maximum of those is used as the resolved 1fr length (the flex fraction), which is then multiplied by each grid track’s flex factor to determine its final size.

5.1.4 Subgrids: the subgrid keyword

A grid item can itself be a grid container by giving it display: grid; in this case the layout of its contents will be independent of the layout of the grid it participates in.

In some cases it might be necessary for the contents of multiple grid items to align to each other. A grid container that is itself a grid item can defer the definition of its rows or columns to its parent grid container by using the subgrid keyword in grid-template-rows and/or grid-template-columns, making it a subgrid in that dimension. In this case, the grid items of the subgrid participate in sizing the grid of the parent grid container, allowing the contents of both grids to align.

For example, suppose we have a form consisting of a list of inputs with labels:
<ul>
  <li><label>Name:</label> <input name=fn>
  <li><label>Address:</label> <input name=address>
  <li><label>Phone:</label> <input name=phone>
</ul>

We want the labels and inputs to align, and we want to style each list item with a border. This can be accomplished with subgrid layout:

ul {
  display: grid;
  grid-auto-flow: row;
  grid-template-columns: auto 1fr;
}
li {
  display: grid;
  grid: subgrid;
  margin: 0.5em;
  border: solid;
  padding: 0.5em;
}
label {
  grid-column: 1;
}
input {
  grid-column: 2;
}

A subgrid behaves just like a normal grid container except that:

5.1.5 Resolved Values

When an element’s display is grid or inline-grid and it generates a box, the resolved value of the grid-template-rows and grid-template-columns properties is the used value, serialized as follows:

Otherwise, (e.g. when the element has display: none or is not a grid) the resolved value is simply the computed value.

<style>
  #grid {
  width: 500px;
  grid-template-columns:
    (a)     auto
    (b)     minmax(min-content, 1fr)
    (b c d) repeat(2, (e) 40px)
        repeat(5, auto);
  }
</style>
<div id="grid">
  <div style="grid-column-start:1; width:50px"></div>
  <div style="grid-column-start:9; width:50px"></div>
</div>
<script>
  var gridElement = document.getElementById("grid");
  getComputedStyle(gridElement).gridDefinitionColumns;
  // (a) 50px (b) 320px (b c d) repeat(2, (e) 40px) repeat(4, 0px) 50px
</script>

Note: In general, resolved values are the computed values, except for a small list of legacy 2.1 properties. However, compatibility with early implementations of this module requires us to define grid-template-rows and grid-template-columns as returning used values. Authors are recommended to use the .rawComputedStyle and .usedStyle attributes instead of getComputedStyle().

5.2 Named Areas: the grid-template-areas property

Name:grid-template-areas
Value:none | <string>+
Initial:none
Applies to:grid containers
Inherited:no
Media:visual
Computed value:specified value
Percentages:n/a

This property specifies named grid areas, which are not associated with any particular grid item, but can be referenced from the grid-placement properties. The syntax of the grid-template-areas property also provides a visualization of the structure of the grid, making the overall layout of the grid container easier to understand.

Values have the following meanings:

none
The grid container doesn’t define any named grid areas.
<string>+
A row is created for every separate string listed for the grid-template-areas property, and a column is created for each cell in the string, when parsed as follows:

Tokenize the string into a list of the following tokens, using longest-match semantics:

Note: These rules can produce cell names that do not match the <ident> syntax, such as "1st 2nd 3rd", which requires escaping when referencing those areas by name in other properties, like grid-row: \31st; to reference the area named 1st.

All strings must have the same number of columns, or else the declaration is invalid. If a named grid area spans multiple grid cells, but those cells do not form a single filled-in rectangle, the declaration is invalid.

Note: Non-rectangular or disconnected regions may be permitted in a future version of this module.

In this example, the grid-template-areas property is used to create a page layout where areas are defined for header content (head), navigational content (nav), footer content (foot), and main content (main). Accordingly, the template creates three rows and two columns, with four named grid areas. The head area spans both columns and the first row of the grid.
<style type="text/css">
  #grid {
  display: grid;
  grid-template-areas: "head head"
             "nav  main"
             "foot .   "
  }
  #grid > header { grid-area: head; }
  #grid > nav    { grid-area: nav; }
  #grid > main   { grid-area: main; }
  #grid > footer { grid-area: foot; }
</style>

5.2.1 Implicit Named Lines

The grid-template-areas property creates implicit named lines from the named grid areas in the template. For each named grid area foo, four implicit named lines are created: two named foo-start, naming the row-start and column-start lines of the named grid area, and two named foo-end, naming the row-end and column-end lines of the named grid area.

These named lines behave just like any other named line, except that they do not appear in the value of grid-template-rows/grid-template-columns. Even if an explicit line of the same name is defined, the implicit named lines are just more lines with the same name.

5.2.2 Implicit Named Areas

Since a named grid area is referenced by the implicit named lines it produces, explicitly adding named lines of the same form (foo-start/foo-end) effectively creates a named grid area. Such implicit named areas do not appear in the value of grid-template-areas, but can still be referenced by the grid-placement properties.

5.3 Explicit Grid Shorthand: the grid-template property

Name:grid-template
Value:none | subgrid | <‘grid-template-columns’> / <‘grid-template-rows’> |
[ <track-list> / ]? [ <line-names>? <string> <track-size>? <line-names>? ]+
Initial:see individual properties
Applies to:grid containers
Inherited:see individual properties
Media:visual
Computed value:see individual properties
Percentages:see individual properties

The grid-template property is a shorthand for setting grid-template-columns, grid-template-rows, and grid-template-areas in a single declaration. It has several distinct syntax forms:

none
Sets all three properties to their initial values (none).
subgrid
Sets grid-template-rows and grid-template-columns to subgrid, and grid-template-areas to its initial value.
<‘grid-template-columns’> / <‘grid-template-rows’>
Sets grid-template-columns and grid-template-rows to the specified values, respectively, and sets grid-template-areas to none.
grid-template: auto 1fr auto / auto 1fr;

is equivalent to

grid-template-columns: auto 1fr auto;
grid-template-rows: auto 1fr;
grid-template-areas: none;
[ <track-list> / ]? [ <line-names>? <string> <track-size>? <line-names>? ]+

This syntax allows the author to align track names and sizes inline with their respective grid areas.

grid-template: auto 1fr auto /
  (header-top) "a   a   a"     (header-bottom)
  (main-top) "b   b   b" 1fr (main-bottom);

is equivalent to

grid-template-columns: auto 1fr auto;
grid-template-rows: (header-top) auto (header-bottom main-top) 1fr (main-bottom);
grid-template-areas: "a a a"
           "b b b";

Note: The grid shorthand accepts the same syntax, but also resets the implicit grid properties to their initial values. Unless authors want those to cascade in separately, it is therefore recommended to use grid instead of grid-template.

6 The Implicit Grid

While grid-template and its longhand properties define the explicit grid, grid items can be positioned outside of these bounds. This causes the grid container to generate implicit grid tracks, forming the implicit grid. The grid-auto-rows and grid-auto-columns properties size these implicit grid tracks.

The grid-auto-flow property controls auto-placement of grid items without an explicit position. Once the explicit grid is filled (or if there is no explicit grid) auto-placement will also cause the generation of implicit grid tracks.

Implementations may limit the possible size of the implicit grid. If they do, attempting to position (or auto-position) an item past the maximum size must instead position the item with its corresponding edge at the maximum index, possibly overlapping other items. Attempting to size an item to a span past the maximum size must instead size it with a span equal to the maximum size. It is recommended that the maximum size of the implicit grid not be smaller than 1 million tracks in each axis.

6.1 Sizing Auto-generated Rows and Columns: the grid-auto-rows and grid-auto-columns properties

Name:grid-auto-columns, grid-auto-rows
Value:<track-size>
Initial:auto
Applies to:grid containers
Inherited:no
Media:visual
Computed value:see Track Sizing
Percentages:see Track Sizing

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

This example illustrates the sizing of implicit grid tracks. Note that grid item B is positioned on grid line 5, which automatically creates four implicit grid columns. However, only two of them (the first and the last) are occupied by any grid items, so the two empty grid tracks collapse to zero width.
A Grid with an implicit row and four implicit columns, two of which are zero-sized.
<style type="text/css">
  #grid {
    display: grid;
    grid-template-columns: 20px;
    grid-template-rows: 20px }
  #A { grid-column: 1;          grid-row: 1; }
  #B { grid-column: 5;          grid-row: 1 / span 2; }
  #C { grid-column: 1 / span 2; grid-row: 2; }
</style>
<div id="grid">
  <div id="A">A</div>
  <div id="B">B</div>
  <div id="C">C</div>
</div>

6.2 Automatic Placement: the grid-auto-flow property

Name:grid-auto-flow
Value:[ row | column ] && dense? | stack && [ row | column ]?
Initial:row
Applies to:grid containers
Inherited:no
Media:visual
Computed value:specified value
Percentages:n/a

Grid items that aren’t explicitly placed are automatically placed into an unoccupied space in the grid container. The grid-auto-flow property controls the direction in which the search for unoccupied space takes place, and whether rows or columns are added as needed to accommodate the content.

row
The auto-placement algorithm places items by filling each row in turn, adding new rows as necessary.
column
The auto-placement algorithm places items by filling each column in turn, adding new columns as necessary.
dense
If specified, the auto-placement algorithm uses a "dense" packing algorithm, which attempts to fill in holes in the grid if smaller items come up later. (By default, the auto-placement algorithm is "sparse", permanently skipping spaces that it can’t fill with the current grid item.)

Note: This may cause items to appear out-of-order.

stack
The auto-placement algorithm is run with a single hypothetical 1×1 grid item, as if grid-auto-flow: row or grid-auto-flow: column were specified, depending on whether row or column is specified alongside it, respectively. If neither row nor column are specified, it defaults to running the algorithm as if grid-auto-flow: row were specified.

Wherever the hypothetical item would be placed, all auto-placed items are placed there, stacked atop one another. (This happens even if the auto-placed item is greater than 1×1, even if doing so would cause it to overlap explicitly-placed grid items.)

Need to clarify what "placed there" means. (See the auto-placement algorithm for details.)

Note: A future level of this module is expected to add a value that flows auto-positioned items together into a single “default” cell.

Auto-placement takes grid items in order-modified document order.

In the following example, there are three columns, each auto-sized to their contents. No rows are explicitly defined. The grid-auto-flow property is row which instructs the grid to search across its three columns starting with the first row, then the next, adding rows as needed until sufficient space is located to accommodate the position of any auto-placed grid item.
Image: A form arranged using automatic placement.

A form arranged using automatic placement.

<style type="text/css">
  form {
  display: grid;
  /* Define three columns, all content-sized,
     and name the corresponding lines. */
  grid-template-columns: (labels) auto (controls) auto (oversized) auto;
  grid-auto-flow: row;
  }
  form > label {
  /* Place all labels in the "labels" column and
     automatically find the next available row. */
  grid-column: labels;
  grid-row: auto;
  }
  form > input, form > select {
  /* Place all controls in the "controls" column and
     automatically find the next available row. */
  grid-column: controls;
  grid-row: auto;
  }
  #department {
  /* Auto place this item in the "oversized" column
     in the first row where an area that spans three rows
     won’t overlap other explicitly placed items or areas
     or any items automatically placed prior to this area. */
  grid-column: oversized;
  grid-row: span 3;
  }
  /* Place all the buttons of the form
   in the explicitly defined grid area. */
  #buttons {
  grid-row: auto;
  /* Ensure the button area spans the entire grid element
     in the row axis. */
  grid-column: 1 / -1;
  text-align: end;
  }
</style>
<form>
  <label for="firstname">First name:</label>
  <input type="text" id="firstname" name="firstname" />
  <label for="lastname">Last name:</label>
  <input type="text" id="lastname" name="lastname" />
  <label for="address">Address:</label>
  <input type="text" id="address" name="address" />
  <label for="address2">Address 2:</label>
  <input type="text" id="address2" name="address2" />
  <label for="city">City:</label>
  <input type="text" id="city" name="city" />
  <label for="state">State:</label>
  <select type="text" id="state" name="state">
  <option value="WA">Washington</option>
  </select>
  <label for="zip">Zip:</label>
  <input type="text" id="zip" name="zip" />
  <div id="department">
  <label for="department">Department:</label>
  <select id="department" name="department" multiple>
    <option value="finance">Finance</option>
    <option value="humanresources">Human Resources</option>
    <option value="marketing">Marketing</option>
  </select>
  </div>
  <div id="buttons">
  <button id="cancel">Cancel</button>
  <button id="back">Back</button>
  <button id="next">Next</button>
  </div>
</form>

7 Grid Definition Shorthand: the grid property

Name:grid
Value:<‘grid-template’> | [ <‘grid-auto-flow’> [ <‘grid-auto-columns’> [ / <‘grid-auto-rows’> ]? ]? ]
Initial:see individual properties
Applies to:grid containers
Inherited:see individual properties
Media:visual
Computed value:see individual properties
Percentages:see individual properties

The grid property is a shorthand that sets all of the explicit grid properties (grid-template-rows, grid-template-columns, and grid-template-areas) as well as all the implicit grid properties (grid-auto-rows, grid-auto-columns, and grid-auto-flow) in a single declaration. If <‘grid-auto-rows’> value is omitted, it is set to the value specified for grid-auto-columns. Other omitted values are set to their initial values.

Note: Note that you can only specify the explicit or the implicit grid properties in a single grid declaration. The sub-properties you don’t specify are set to their initial value, as normal for shorthands.

In addition to accepting the grid-template shorthand syntax for setting up the explicit grid, the grid shorthand can also easily set up parameters for an auto-formatted grid. For example, grid: row 1fr; is equivalent to
grid-template: none;
grid-auto-columns: 1fr;
grid-auto-rows: 1fr;
grid-auto-flow: row;

Similarly, grid: column 1fr / auto is equivalent to

grid-template: none;
grid-auto-columns: 1fr;
grid-auto-rows: auto;
grid-auto-flow: column;

8 Placing Grid Items

A grid item’s placement consists of a grid position and a grid span:

grid position
The grid item’s location in the grid. A grid position can be either definite (explicitly specified) or automatic (determined by auto-placement).
grid span
How many grid tracks the grid item occupies. A subgrid’s grid span can be automatic (determined by its implicit grid) if not specified or implied; a grid item’s grid span is otherwise always definite (defaulting to 1).

The grid-placement propertiesthe longhands grid-row-start, grid-row-end, grid-column-start, grid-column-end, and their shorthands grid-row, grid-column, and grid-areaallow the author to specify a grid item’s placement by providing any (or none) of the following six pieces of information:

Row Column
Start row-start line column-start line
End row-end line column-end line
Span row span column span

A definite value for any two of Start, End, and Span in a given dimension implies a definite value for the third.

The following table summarizes the conditions under which a grid position or span is definite or automatic:

Position Span
Definite At least one specified line Explicit, implicit, or defaulted span.
Note: Non-subgrids default to 1.
Automatic No lines explicitly specified Subgrid without an explicit or implied span

8.1 Common Patterns for Grid Placement

This section is informative.

The grid-placement property longhands are organized into three shorthands:

grid-area
grid-column grid-row
grid-column-start grid-column-end grid-row-start grid-row-end

8.1.1 Named Areas

An item can be placed into a named grid area (such as those produced by the template in grid-template-areas) by specifying the area’s name in grid-area:

article {
  grid-area: main;
  /* Places item into the named area "main". */
}

An item can also be partially aligned with a named grid area, with other edges aligned to some other line:

.one {
  grid-row-start: main;
  /* Align the row-start edge to the start edge of the "main" named area. */
}

8.1.2 Numeric Indexes and Spans

Grid items can be positioned and sized by number, which is particularly helpful for script-driven layouts:

.two {
  grid-row: 2;    /* Place item in the second row. */
  grid-column: 3; /* Place item in the third column. */
  /* Equivalent to grid-area: 2 / 3;
}

By default, a grid item has a span of 1. Different spans can be given explicitly:

.three {
  grid-row: 2 / span 5;
  /* Starts in the 2nd row,
     spans 5 rows down (ending in the 7th row). */
}
.four {
  grid-row: span 5 / 7;
  /* Ends in the 7th row,
     spans 5 rows up (starting in the 2nd row). */
}

Note: Note that grid indexes are writing mode relative. For example, in a right-to-left language like Arabic, the first column is the rightmost column.

8.1.3 Named Lines and Spans

Instead of counting lines by number, named lines can be referenced by their name:

.five {
  grid-column: first / middle;
  /* Span from line "first" to line "middle". */
}

Note: Note that if a named grid area and a named line have the same name, the placement algorithm will prefer to use named grid area’s edge instead.

If there are multiple lines of the same name, they effectively establish a named set of grid lines, which can be exclusively indexed by filtering the placement by name:

.six {
  grid-row: text 5 / text 7;
  /* Span between the 5th and 7th lines named "text". */
  grid-row: text 5 / span text 2;
  /* Same as above. */
}

8.1.4 Auto Placement

A grid item can be automatically placed into the next available empty grid cell, growing the grid if there’s no space left.

.eight {
  grid-area: auto; /* Initial value */
}

This can be used, for example, to list a number of sale items on a catalog site in a grid pattern.

Auto-placement can be combined with an explicit span, if the item should take up more than one cell:

.nine {
  grid-area: span 2 / span 3;
  /* Auto-placed item, covering two rows and three columns. */
}

Whether the auto-placement algorithm searchs across and adds rows, or searches across and adds columns, is controlled by the grid-auto-flow property.

Note: By default, the auto-placement algorithm looks linearly through the grid without backtracking; if it has to skip some empty spaces to place a larger item, it will not return to fill those spaces. To change this behavior, specify the dense keyword in grid-auto-flow.

8.1.5 Auto Sizing Subgrids

A subgrid without a definite grid span is sized to its implicit grid, i.e. all of its items within it are first placed into its own grid, and its span is the resulting size of its grid.

For example, a subgrid spanning two columns can be given an auto-spanning block size:
.adverts {
  grid: subgrid;
  grid-column: span 2;
}

If it contains 10 auto-placed items, it will span 5 rows in its parent grid.

Note: Since auto-spanning subgrids determine their span before being positioned, they can also be auto-positioned. The above example would auto-place the .adverts block, if no further rules specified its position.

8.2 Line-based Placement: the grid-row-start, grid-column-start, grid-row-end, and grid-column-end properties

Name:grid-row-start, grid-column-start, grid-row-end, grid-column-end
Value:<grid-line>
Initial:auto
Applies to:grid items
Inherited:no
Media:visual
Computed value:specified value
Percentages:n/a
<grid-line> =
  auto |
  <custom-ident> |
  [ <integer> && <custom-ident>? ] |
  [ span && [ <integer> || <custom-ident> ] ]

The grid-row-start, grid-column-start, grid-row-end, and grid-column-end properties determine a grid item’s size and location within the grid by contributing a line, a span, or nothing (automatic) to its grid placement, thereby specifying the inline-start, block-start, inline-end, and block-end edges of its grid area.

Values have the following meanings:

<custom-ident>
First attempt to match the grid area’s edge to a named grid area: if there is a named line with the name ''<custom-ident>-start (for grid-*-start) / <custom-ident>-end'' (for grid-*-end), contributes the first such line to the grid item’s placement.

Note: Named grid areas automatically generate implicit named lines of this form, so specifying grid-row-start: foo will choose the start edge of that named grid area (unless another line named foo-start was explicitly specified before it).

Otherwise, treat this as if the integer 1 had been specified along with the <custom-ident>.

<integer> && <custom-ident>?
Contributes the Nth grid line to the grid item’s placement. If a negative integer is given, it instead counts in reverse, starting from the end edge of the explicit grid.

If a name is given as a <custom-ident>, only lines with that name are counted. If not enough lines with that name exist, all lines in the implicit grid are assumed to have that name for the purpose of finding this position.

A <integer> value of zero makes the declaration invalid.

span && [ <integer> || <custom-ident> ]
Contributes a grid span to the grid item’s placement such that the corresponding edge of the grid item’s grid area is N lines from its opposite edge.

If a name is given as a <custom-ident>, only lines with that name are counted. If not enough lines with that name exist, all lines in the implicit grid are assumed to have that name for the purpose of counting this span.

If the <integer> is omitted, it defaults to 1. Negative integers or zero are invalid.

auto
The property contributes nothing to the grid item’s placement, indicating auto-placement, an automatic span, or a default span of one. (See Placing Grid Items, above.)
Given a single-row, 8-column grid and the following 9 named lines:
1  2  3  4  5  6  7  8  9
+--+--+--+--+--+--+--+--+
|  |  |  |  |  |  |  |  |
A  B  C  A  B  C  A  B  C
|  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+--+

The following declarations place the grid item between the lines indicated by index:

grid-column-start: 4; grid-column-end: auto;
/* Line 4 to line 5 */
grid-column-start: auto; grid-column-end: 6;
/* Line 5 to line 6 */
grid-column-start: C; grid-column-end: C -1;
/* Line 3 to line 9 */
grid-column-start: C; grid-column-end: span C;
/* Line 3 to line 6 */
grid-column-start: span C; grid-column-end: C -1;
/* Line 6 to line 9 */
grid-column-start: span C; grid-column-end: span C;
/* Error: The end span is ignored, and an auto-placed
   item can’t span to a named line.
   Equivalent to grid-column: span 1;. */
grid-column-start: 5; grid-column-end: C -1;
/* Line 5 to line 9 */
grid-column-start: 5; grid-column-end: span C;
/* Line 5 to line 6 */
grid-column-start: 8; grid-column-end: 8;
/* Error: line 8 to line 9 */
grid-column-start: B 2; grid-column-end: span 1;
/* Line 5 to line 6 */

8.2.1 Grid Placement Conflict Handling

If grid-row-end/grid-column-end specifies a line at or before that specified by grid-row-start/grid-column-start, it instead contributes nothing.

If both grid-row-start and grid-row-end, or grid-column-start and grid-column-end, specify a span, the end span is ignored.

If the grid item has an automatic position and a grid span for a named line in a given dimension, instead treat the grid span as one.

8.3 Placement Shorthands: the grid-column, grid-row, and grid-area properties

Name:grid-row, grid-column
Value:<grid-line> [ / <grid-line> ]?
Initial:see individual properties
Applies to:grid items
Inherited:see individual properties
Media:visual
Computed value:see individual properties
Percentages:see individual properties

The grid-row and grid-column properties are shorthands for grid-row-start/grid-row-end and grid-column-start/grid-column-end, respectively.

If two <grid-line> values are specified, the grid-row-start/grid-column-start longhand is set to the value before the slash, and the grid-row-end/grid-column-end longhand is set to the value after the slash.

When the second value is omitted, if the first value is a <custom-ident>, the grid-row-end/grid-column-end longhand is also set to that <custom-ident>; otherwise, it is set to auto.

Name:grid-area
Value:<grid-line> [ / <grid-line> ]{0,3}
Initial:see individual properties
Applies to:grid items
Inherited:see individual properties
Media:visual
Computed value:see individual properties
Percentages:see individual properties

If four <grid-line> values are specified, grid-row-start is set to the first value, grid-column-start is set to the second value, grid-row-end is set to the third value, and grid-column-end is set to the fourth value.

When grid-column-end is omitted, if grid-column-start is a <custom-ident>, grid-column-end is set to that <custom-ident>; otherwise, it is set to auto.

When grid-row-end is omitted, if grid-row-start is a <custom-ident>, grid-row-end is set to that <custom-ident>; otherwise, it is set to auto.

When grid-column-start is omitted, if grid-row-start is a <custom-ident>, all four longhands are set to that value. Otherwise, it is set to auto.

Note: The resolution order for this shorthand is row-start/column-start/row-end/column-end, which goes CCW for LTR pages, the opposite direction of the related 4-edge properties using physical directions, like margin.

8.4 Absolutely-positioned Grid Items

If an absolutely positioned element’s containing block is generated by a grid container, its containing block edges are the edges of the element’s grid area as given by its grid-placement properties. In this case, an auto value for a grid-placement property contributes the corresponding padding edge of the grid container as a line. (Thus, by default, the containing block will correspond to the padding edges of the grid container.) The offset properties (top/right/bottom/left) then indicate offsets inwards from the corresponding edges of the resulting containing block, as normal.

Note: Note that, while absolutely-positioning an element to a grid container does allow it to align to that container’s grid lines, such elements do not take up space or otherwise participate in the layout of the grid.

.grid {
  grid: 10rem 10rem 10rem 10rem / 1fr 1fr 1fr 1fr;
  /* 4 columns of 10rem each,
     4 equal-height rows filling the grid container */
  justify-content: center;
  /* center the grid horizontally within the grid container */
  position: relative;
  /* Establish abspos containing block */
}
.abspos {
  grid-row-start: 1;     /* 1st grid row line = top of grid container */
  grid-row-end: span 2;  /* 3rd grid row line */
  grid-column-start: 3;  /* 3rd grid col line */
  grid-column-end: auto; /* right padding edge */
  /* Containing block covers the top right quadrant of the grid container */
  position: absolute;
  top: 70px;
  bottom: 40px;
  left: 100px;
  right: 30px;
}

Note: Note that grids and the grid-placement properties are flow-relative, while abspos offsets are physical, so if the direction or writing-mode properties change, the grid will transform to match, but the offsets won’t.

8.5 Grid Item Placement Algorithm

The following grid item placement algorithm assigns grid items to grid cells such that all items in the grid container are given a definite grid position. It places first all explicitly-positioned items, then items with automatic grid positions, adding rows/columns as necessary to contain all of the grid items.

To aid in clarity, this algorithm is written with the assumption that grid-auto-flow is set to row. If it is instead set to column, swap all mentions of rows and columns in this algorithm.

For the purpose of this algorithm, an occupied grid cell is any grid cell which is contained within any named grid area or the grid area of any previously-positioned grid item.

  1. Position anything that’s not auto-positioned.

    Before auto-positioning anything, position every grid item with a definite grid position in both axes.

  2. Process the items locked to a given row.

    For each grid item with a definite row position (that is, the grid-row-start and grid-row-end properties define a definite grid position), in order-modified document order, position its inline-start edge to the earliest (smallest positive index) line index that ensures this item’s grid area will not overlap any occupied grid cells.

  3. Determine the number of columns in the implicit grid.

    Set the number of columns in the implicit grid to the larger of:

    For example, in the following style fragment:
    #grid {
      display: grid;
      grid-template-columns: repeat(5, 100px);
      grid-auto-flow: row;
    }
    #grid-item {
      grid-column: 4 / span 3;
    }
    

    The number of columns needed is 6. The #grid-item element’s inline-start edge is positioned at index 4, so its span ensures that it’s inline-end edge will be positioned at index 7. This requires 7 - 1 = 6 columns to hold, which is larger than the explicit grid’s 5 columns.

  4. Position the remaining grid items.

    The auto-placement cursor defines the current "insertion point" in the grid, specified as a pair of row and column grid lines. Initially the auto-placement cursor at is specified with a row and column position both equal to 1.

    For each grid item that hasn’t been positioned by the previous steps, in order-modified document order:

    If the item has a definite column position:
    1. Set the column position of the cursor to be equal to the inline-start index of the grid item.
    2. Increment the auto-placement cursor’s row position until a value is found where the grid item does not overlap any occupied grid cells (creating new rows in the implicit grid as necessary). Position the item’s block-start edge to the auto-placement cursor’s row position.
    If the item has an automatic grid position in both axes:
    1. Increment the column position of the auto-placement cursor until this item’s grid area does not overlap any occupied grid cells or overflow the number of columns determined in the previous step.
    2. If a non-overlapping position was found in the previous step, position the item’s inline-start and block-start edges to the auto-placement cursor’s column and row position, respectively Otherwise, increment the auto-placement cursor’s row position (creating new rows in the implicit grid as necessary), set its column position to 1, and return to the previous step.

    This needs to be setting up the containing block for the item, not explicitly positioning the item’s edges. (Alignment properties can change where in the specified area it actually sits.)

    If grid-auto-flow specifies the dense keyword, reset the auto-placement cursor to 1/1 each time an item is placed.

9 Alignment

After a grid container’s grid tracks have been sized, and the dimensions of all grid items are finalized, grid items can be aligned within their grid areas.

The margin properties can be used to align items in a manner similar to, but more powerful than, what margins can do in block layout. Grid items also respect the alignment properties from the Box Alignment spec, which allow easy keyword-based alignment of items in both the row axis and column axis.

By default, grid items stretch to fill their grid area. However, if justify-self or align-self compute to a value other than stretch or margins are auto, grid items will auto-size to fit their contents.

9.1 Aligning with auto margins

This section is non-normative. The normative definition of how margins affect grid items is in §10 Track Sizing Algorithm.

Auto margins on grid items have an effect very similar to auto margins in block flow:

Note: Note that, if free space is distributed to auto margins, the alignment properties will have no effect in that dimension because the margins will have stolen all the free space left over after sizing.

TODO: EXAMPLE HERE

9.2 Row-axis Alignment: the justify-self and justify-items properties

Grid items can be aligned in the inline dimension by using the justify-self property on the grid item or justify-items property on the grid container, as defined in [CSS3-ALIGN].

For example, for an English document, the inline axis is horizontal, and so the justify-* properties align the grid items horizontally.

TODO: provide example

9.3 Column-axis Alignment: the align-self and align-items properties

Grid items can also be aligned in the block dimension (perpendicular to the inline dimension) by using the align-self property on the grid item or align-items property on the grid container, as defined in [CSS3-ALIGN].

9.4 Aligning the Grid: the justify-content and align-content properties

If the grid’s outer edges do not correspond to the grid container’s content edges (for example, if no columns are flex-sized), the grid is aligned within the content box according to the justify-content and align-content properties on the grid container.

For example, the following grid is centered vertically, and aligned to the right edge of its grid container:
.grid {
  display: grid;
  grid: 12rem 12rem 12rem 12rem / 10rem 10rem 10rem 10rem;
  justify-content: end;
  align-content: center;
}

9.5 Z-axis Ordering: the z-index property

Grid items can overlap when they are positioned into intersecting grid areas, or even when positioned in non-intersecting areas because of negative margins or positioning. The painting order of grid items is exactly the same as inline blocks [CSS21], except that order-modified document order is used in place of raw document order, and z-index values other than auto create a stacking context even if position is static. Thus the z-index property can easily be used to control the z-axis order of grid items.

Note: Descendants that are positioned outside a grid item still participate in any stacking context established by the grid item.

The following diagram shows several overlapping grid items, with a combination of implicit source order and explicit z-index used to control their stacking order.
Drawing order controlled by z-index and source order.
<style type="text/css">
  #grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  grid-template-rows: 1fr 1fr
  }
  #A { grid-column: 1 / span 2; grid-row: 2; align-self: end; }
  #B { grid-column: 1; grid-row: 1; z-index: 10; }
  #C { grid-column: 2; grid-row: 1; align-self: start; margin-left: -20px; }
  #D { grid-column: 2; grid-row: 2; justify-self: end; align-self: start; }
  #E { grid-column: 1 / span 2; grid-row: 1 / span 2;
     z-index: 5; justify-self: center; align-self: center; }
</style>
<div id="grid">
  <div id="A">A</div>
  <div id="B">B</div>
  <div id="C">C</div>
  <div id="D">D</div>
  <div id="E">E</div>
</div>

9.6 Grid Baselines

The baselines of a grid container are determined as follows:

  1. If any of the grid items whose areas intersect the grid container’s first row/column participate in baseline alignment, the grid container’s baseline is the baseline of those grid items.
  2. Otherwise, if the grid container has at least one grid item whose area intersects the first row/column, and the first such grid item (in order-modified grid order) has a baseline parallel to the relevant axis, the grid container’s baseline is that baseline.
  3. Otherwise, the grid container’s baseline is synthesized from the first item’s (in order-modified grid order) content box, or, failing that, from the grid container’s content box.

A grid item participates in baseline alignment in a particular dimension if its value for align-self or justify-self, as appropriate, is baseline and its inline axis is parallel to that dimension.

order-modified grid order is the order in which grid items are encountered when traversing the grid’s grid cells, in row-major order if calculating the inline-axis baseline, or in column-major order if calculating the block-axis baseline. If two items are encountered at the same time, they are taken in order-modified document order.

When calculating the baseline according to the above rules, if the box contributing a baseline has an overflow value that allows scrolling, the box must be treated as being in its initial scroll position for the purpose of determining its baseline.

When determining the baseline of a table cell, a grid container provides a baseline just as a line box or table-row does. [CSS21]

10 Track Sizing Algorithm

10.1 Definition of Terms for use in Calculating Grid Track Sizes

min track sizing function
If the track was sized with a minmax() function, this is the first argument to that function. Otherwise, it’s the track’s sizing function.
max track sizing function
If the track was sized with a minmax() function, this is the second argument to that function. Otherwise, it’s the track’s sizing function.
available space
The grid container’s content box size in the applicable dimension.
free space
Equal to the available space minus the sum of the base sizes of all the grid tracks, clamped to a minimum of zero. This value can change over the course of the algorithm, as base sizes are adjusted.

If available space is indefinite, the free space is indefinite as well.

span count
The number of grid tracks crossed by a grid item in the applicable dimension.

10.2 Overall Sizing Algorithm

Each track has specified minimum and maximum sizing functions (which may be the same). Each sizing function is either:

The grid layout algorithm defines how to resolve these sizing constraints into used track sizes.

  1. First, the track sizing algorithm is used to resolve the sizes of the grid columns.
  2. Next, the track sizing algorithm resolves the sizes of the grid rows.
  3. Then, if the min-content contribution of any grid items have changed based on the row sizes calculated in step 2, steps 1 and 2 are repeated with the new min-content contribution (once only).

    What is this solving and is this the right solution?

Once the size of each grid area is thus established, the grid items are laid out into their respective containing blocks.

The remainder of this section is the track sizing algorithm, which calculates from the min and max track sizing functions the used track size. Each track has a base size, a <length> which grows throughout the algorithm and which will eventually be the track’s final size, and a growth limit, a <length> which provides a desired maximum size for the base size. (The base size might end up being larger than the growth limit, but the algorithm attempts to avoid this situation.) There are 4 steps:

  1. Initialize Track Sizes
  2. Resolve Content-Based Track Sizing Functions
  3. Grow All Tracks To Their Max
  4. Process Flexible Tracks

Make sure orthogonal flows are correctly addressed. (discussion)

10.3 Initialize Track Sizes

Initialize each track’s base size and growth limit. For each track, if the track’s min track sizing function is:

A fixed sizing function
Resolve to an absolute length and use that size as the track’s initial base size.

Note: Indefinite lengths cannot occur, as they’re treated as auto.

An intrinsic sizing function
A flexible sizing function
Use an initial base size of zero.

For each track, if the track’s max track sizing function is:

A fixed sizing function
Resolve to an absolute length and use that size as the track’s initial growth limit.
An intrinsic sizing function
Use an initial growth limit of infinity.
A flexible sizing function
Use the track’s initial base size as its initial growth limit.

10.4 Resolve Content-Based Track Sizing Functions

This step resolves intrinsic track sizing functions to absolute lengths. First it resolves those sizes based on items that are contained wholly within a single track. Then it gradually adds in the space requirements of items that span multiple tracks, evenly distributing the extra space across those tracks insofar as possible.

When the grid container is being sized under a min-content constraint, a track with a flexible min track sizing function is treated as if its min track sizing function was min-content for the purposes of this step. This seems correct, but should be checked because it wasn’t in the original algorithm.

Note: There is no single way to satisfy these constraints when items span across multiple tracks. This algorithm embodies a number of heuristics which have been seen to deliver good results on real-world use-cases, such as the "game" examples earlier in this specification. This algorithm may be updated in the future to take into account more advanced heuristics as they are identified.

  1. Size tracks to fit non-spanning items: For each track with an intrinsic track sizing function, consider the items in it with a span of 1:
  2. Increase sizes to accommodate spanning items: Next, consider the items with a span of 2 that do not span a track with a flexible sizing function:
    1. For intrinsic minimums: First increase the base size of tracks with a min track sizing function of min-content or max-content by distributing extra space as needed to account for these items' min-content contributions.
    2. For max-content minimums: Next continue to increase the base size of tracks with a min track sizing function of max-content by distributing extra space as needed to account for these items' max-content contributions.
    3. For intrinsic maximums: Third increase the growth limit of tracks with a max track sizing function of min-content or max-content by distributing extra space as needed to account for these items' min-content contributions. Mark any tracks whose growth limit changed from infinite to finite in this step as infinitely growable for the next step.
    4. For max-content maximums: Lastly continue to increase the growth limit of tracks with a max track sizing function of max-content by distributing extra space as needed to account for these items' max-content contributions.

    Repeat incrementally for items with greater spans until all items have been considered.

To distribute extra space by increasing the affected sizes of a set of tracks as required by a set of intrinsic size contributions,

  1. Maintain separately for each affected base size or growth limit an amount of planned increase. (This prevents the size increases from becoming order-dependent.)
  2. For each considered item,
    1. Find the space to distribute: Subtract the corresponding size (base size or growth limit) of every spanned track from the item’s size contribution to find the the item’s remaining size contribution. (For infinite growth limits, substitute the track’s base size.) This is the space to distribute. Floor it at zero.
      extra-space = max(0, size-contribution - ∑track-sizes)
    2. Distribute space to base sizes up to growth limits: Distribute the space equally to the planned increase of each spanned track with an affected size, freezing tracks as their planned size reaches their growth limits (and continuing to grow the unfrozen tracks as needed).

      If a track was marked as infinitely growable for this phase, treat its growth limit as infinite for this calculation (and then unmark it).

      Note: If the affected size was a growth limit, this step has no effect.

    3. Distribute space beyond growth limits: If space remains after all tracks are frozen, unfreeze and continue to distribute space to…
    4. Update the tracks' affected sizes by folding in the calculated increase so that the next round of space distribution will account for the increase. (If the affected size is infinite, set it to the track’s base size plus the calculated increase.)

Note: When this step is complete, all intrinsic base sizes and growth limits will have been resolved to absolute lengths.

10.5 Grow All Tracks To Their Max

If the free space is positive, distribute it equally to all tracks, freezing tracks as they reach their growth limits (and continuing to grow the unfrozen tracks as needed).

For the purpose of this step: if sizing the grid container under a max-content constraint, the free space is infinite; if sizing under a min-content constraint, the free space is zero.

10.6 Process Flexible Tracks

This step sizes flexible tracks using the largest value it can assign to an fr without exceeding the available space.

First, find the used flex fraction:

If the free space is zero:
The used flex fraction is zero.

If the free space is a definite length:
The used flex fraction is the result of finding the size of an fr using all of the grid tracks and a space to fill of the available space.
If the free space is an indefinite length:
The used flex fraction is the maximum of:

For each flexible track, if the product of the used flex fraction and the track’s flex factor is greater than the track’s base size, set its base size to that product.

10.6.1 Find the Size of an fr

This algorithm finds the largest size that an fr unit can be without exceeding the target size. It must be called with a set of grid tracks and some quantity of space to fill.

  1. Let leftover space be the space to fill minus the base sizes of the non-flexible grid tracks.
  2. Let the hypothetical flex fraction be the leftover space divided by the sum of the flex factors of the flexible tracks.
  3. If the product of the hypothetical flex fraction and a flexible track’s flex factor is less than the track’s base size, restart this algorithm treating all such tracks as inflexible.
  4. Return the hypothetical flex fraction.

This section needs adjustment to handle sum(flex-factors) < 1 the same way Flexbox now does it.

11 Fragmenting Grid Layout

Fill this in.

Acknowledgements

This specification is made possible by input from Erik Anderson, Rossen Atanassov, Arron Eicholz, Sylvain Galineau, Markus Mielke, John Jansen, Chris Jones, Kathy Kam, Veljko Miljanic, Peter Salas, Christian Stockwell, Eugene Veselov, and the CSS Working Group members. Thanks to Eliot Graff for editorial input.

Changes

The following significant changes were made since the 13 May 2014 Working Draft.

Appendix A: Translated Layout Algorithm

Note: The following is a more direct translation of the original Microsoft editors' track sizing algorithm, from which the current algorithm is derived. It follows the original algorithm structure without being as programmatic in its language. It is preserved here to aid in review of the current specification (and will be removed in the next revision).

This algorithm is run multiple times, once for each set of grid items with a particular span count, and each time it moves through four phases, each one addressing one combination of min-content or max-content as a min track sizing function or max track sizing function.

Starting from the set of all grid items in the grid, remove any with a span count greater than one which span a track with a <flex> max track sizing function. Of the remaining, sort them into groups according to their span count, and order the groups in ascending order of span count. For each group, in order, perform the following steps four times:

  1. Initialize variables.

    Let each item’s needed space be:

    In phase 1
    The min-content size of the item, minus the sum of the base sizes of the grid tracks it spans.
    In phase 2
    The max-content size of the item, minus the sum of the base sizes of the grid tracks it spans.
    In phase 3
    The min-content size of the item, minus the sum of the growth limits of the grid tracks it spans (or, if the growth limit is infinite, the base size).
    In phase 4
    The max-content size of the item, minus the sum of the growth limits of the grid tracks it spans (or, if the growth limit is infinite, the base size).

    Let each item’s growable tracks be:

    In phase 1
    The grid tracks it spans with a min-content or max-content min track sizing function.
    In phase 2
    The grid tracks it spans with a max-content min track sizing function.
    In phase 3
    The grid tracks it spans with a min-content or max-content max track sizing function.
    In phase 4
    The grid tracks it spans with a max-content max track sizing function.

    Let each item’s overgrowable tracks be:

    In phase 1
    The item’s growable tracks that also have a min-content or max-content max track sizing function. If there are no such tracks, then it’s all the growable tracks.
    In phase 2
    The item’s growable tracks that also have a max-content max track sizing function. If there ar eno such tracks, then it’s all the growable tracks.
    In phase 3
    In phase 4
    The item’s growable tracks.

    Let each track’s growth delta initially be zero.

  2. Calculate growth deltas.

    For each grid item in the group:

    1. In phase 1
      In phase 2
      Let each track’s hypothetical size be the track’s base size.
      In phase 3
      In phase 4
      Let each track’s hypothetical size be the track’s growth limit if it’s finite, or else the track’s base size otherwise.
    2. Distribute the item’s needed space as evenly as possible among the hypothetical sizes of the item’s growable tracks, maxing each out as its hypothetical size reaches its growth limit.
      In phase 4
      If the track’s growth limit was changed from infinite to a finite value in phase 3, treat its growth limit as infinite for the purposes of this step.
    3. If all growable tracks reached their growth limit in the previous step and there is still needed space to distribute, distribute the leftover space evenly among the hypothetical sizes of the item’s overgrowable tracks.
    4. In phase 1
      In phase 2
      For each track, if the difference between its hypothetical size and its base size is greater than its growth delta, set its growth delta to that difference.
      In phase 3
      In phase 4
      For each track, if its growth limit is finite, and the difference between its hypothetical size and its growth limit is greater than its growth delta, set its growth delta to that difference. Otherwise, if its growth limit is infinite, and the difference between its hypothetical size and its base size is greater than its growth delta, set its growth delta to that difference.
  3. Adjust each track’s affected size.
    In phase 1
    In phase 2
    For each track, increase its base size by its growth delta.
    In phase 3
    In phase 4
    For each track, if its growth limit is finite, increase its growth limit by its growth delta. Otherwise, if its growth limit is infinite, set its growth limit to the sum of its base size and its growth delta.

Conformance

Document conventions

Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.

All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. [RFC2119]

Examples in this specification are introduced with the words "for example" or are set apart from the normative text with class="example", like this:

This is an example of an informative example.

Informative notes begin with the word "Note" and are set apart from the normative text with class="note", like this:

Note, this is an informative note.

Advisements are normative sections styled to evoke special attention and are set apart from other normative text with <strong class="advisement">, like this: UAs MUST provide an accessible alternative.

Conformance classes

Conformance to this specification is defined for three conformance classes:

style sheet
A CSS style sheet.
renderer
A UA that interprets the semantics of a style sheet and renders documents that use them.
authoring tool
A UA that writes a style sheet.

A style sheet is conformant to this specification if all of its statements that use syntax defined in this module are valid according to the generic CSS grammar and the individual grammars of each feature defined in this module.

A renderer is conformant to this specification if, in addition to interpreting the style sheet as defined by the appropriate specifications, it supports all the features defined by this specification by parsing them correctly and rendering the document accordingly. However, the inability of a UA to correctly render a document due to limitations of the device does not make the UA non-conformant. (For example, a UA is not required to render color on a monochrome monitor.)

An authoring tool is conformant to this specification if it writes style sheets that are syntactically correct according to the generic CSS grammar and the individual grammars of each feature in this module, and meet all other conformance requirements of style sheets as described in this module.

Partial implementations

So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid (and ignore as appropriate) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support. In particular, user agents must not selectively ignore unsupported component values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored.

Experimental implementations

To avoid clashes with future CSS features, the CSS2.1 specification reserves a prefixed syntax for proprietary and experimental extensions to CSS.

Prior to a specification reaching the Candidate Recommendation stage in the W3C process, all implementations of a CSS feature are considered experimental. The CSS Working Group recommends that implementations use a vendor-prefixed syntax for such features, including those in W3C Working Drafts. This avoids incompatibilities with future changes in the draft.

Non-experimental implementations

Once a specification reaches the Candidate Recommendation stage, non-experimental implementations are possible, and implementors should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec.

To establish and maintain the interoperability of CSS across implementations, the CSS Working Group requests that non-experimental CSS renderers submit an implementation report (and, if necessary, the testcases used for that implementation report) to the W3C before releasing an unprefixed implementation of any CSS features. Testcases submitted to W3C are subject to review and correction by the CSS Working Group.

Further information on submitting testcases and implementation reports can be found from on the CSS Working Group’s website at http://www.w3.org/Style/CSS/Test/. Questions should be directed to the public-css-testsuite@w3.org mailing list.

References

Normative References

[CSS21]
Bert Bos; et al. Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification. 7 June 2011. W3C Recommendation. URL: http://www.w3.org/TR/2011/REC-CSS2-20110607
[CSS3-ALIGN]
Elika J. Etemad; Tab Atkins Jr.. CSS Box Alignment Module Level 3. 14 May 2013. W3C Working Draft. (Work in progress.) URL: http://www.w3.org/TR/2013/WD-css3-align-20130514/
[CSS3-SIZING]
Tab Atkins Jr.; Elika J. Etemad. CSS Intrinsic & Extrinsic Sizing Module Level 3. 27 September 2012. W3C Working Draft. (Work in progress.) URL: http://www.w3.org/TR/2012/WD-css3-sizing-20120927/
[CSS3-WRITING-MODES]
Elika J. Etemad; Koji Ishii. CSS Writing Modes Module Level 3. 15 November 2012. W3C Working Draft. (Work in progress.) URL: http://www.w3.org/TR/2012/WD-css3-writing-modes-20121115/
[CSS3VAL]
Håkon Wium Lie; Tab Atkins; Elika J. Etemad. CSS Values and Units Module Level 3. 30 July 2013. W3C Candidate Recommendation. (Work in progress.) URL: http://www.w3.org/TR/2013/CR-css3-values-20130730/
[RFC2119]
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. URL: http://www.ietf.org/rfc/rfc2119.txt

Informative References

[CSS3-FLEXBOX]
Tab Atkins Jr.; Elika J. Etemad; Alex Mogilevsky. CSS Flexible Box Layout Module. 18 September 2012. W3C Candidate Recommendation. (Work in progress.) URL: http://www.w3.org/TR/2012/CR-css3-flexbox-20120918/

Index

Property index

NameValueInitialApplies toInh.%agesMediaComputed value
grid-template-columnsnone | <track-list> | subgrid <line-name-list>?nonegrid containersnorefer to corresponding dimension of the content areavisualAs specified, except for auto (see prose), with lengths made absolute
grid-template-rowsnone | <track-list> | subgrid <line-name-list>?nonegrid containersnorefer to corresponding dimension of the content areavisualAs specified, except for auto (see prose), with lengths made absolute
grid-template-areasnone | <string>+nonegrid containersnon/avisualspecified value
grid-templatenone | subgrid | <‘grid-template-columns’> / <‘grid-template-rows’> | [ <track-list> / ]? [ <line-names>? <string> <track-size>? <line-names>? ]+see individual propertiesgrid containerssee individual propertiessee individual propertiesvisualsee individual properties
grid-auto-columns<track-size>autogrid containersnosee Track Sizingvisualsee Track Sizing
grid-auto-rows<track-size>autogrid containersnosee Track Sizingvisualsee Track Sizing
grid-auto-flow[ row | column ] && dense? | stack && [ row | column ]?rowgrid containersnon/avisualspecified value
grid<‘grid-template’> | [ <‘grid-auto-flow’> [ <‘grid-auto-columns’> [ / <‘grid-auto-rows’> ]? ]? ]see individual propertiesgrid containerssee individual propertiessee individual propertiesvisualsee individual properties
grid-row-start<grid-line>autogrid itemsnon/avisualspecified value
grid-column-start<grid-line>autogrid itemsnon/avisualspecified value
grid-row-end<grid-line>autogrid itemsnon/avisualspecified value
grid-column-end<grid-line>autogrid itemsnon/avisualspecified value
grid-row<grid-line> [ / <grid-line> ]?see individual propertiesgrid itemssee individual propertiessee individual propertiesvisualsee individual properties
grid-column<grid-line> [ / <grid-line> ]?see individual propertiesgrid itemssee individual propertiessee individual propertiesvisualsee individual properties
grid-area<grid-line> [ / <grid-line> ]{0,3}see individual propertiesgrid itemssee individual propertiessee individual propertiesvisualsee individual properties

Issues Index

The block layout spec should define this?
We want the ability to collapse grid tracks (similar to collapsing flex items or table rows/columns), but we’re not sure exactly how to do it. Ideas welcome, please post them to www-style@w3.org.
Need to clarify what "placed there" means. (See the auto-placement algorithm for details.)
This needs to be setting up the containing block for the item, not explicitly positioning the item’s edges. (Alignment properties can change where in the specified area it actually sits.)
TODO: EXAMPLE HERE
TODO: provide example
What is this solving and is this the right solution?
Make sure orthogonal flows are correctly addressed. (discussion)
This seems correct, but should be checked because it wasn’t in the original algorithm.
This section needs adjustment to handle sum(flex-factors) < 1 the same way Flexbox now does it.
Fill this in.