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 predefined flexible or fixed-size layout grid.

For changes since the last draft, see the Changes section.

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This document was produced by the CSS Working Group as a Candidate Recommendation. This document is intended to become a W3C Recommendation. This document will remain a Candidate Recommendation at least until 18 October 2020 in order to ensure the opportunity for wide review.

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

“At-risk” is a W3C Process term-of-art, and does not necessarily imply that the feature is in danger of being dropped or delayed. It means that the WG believes the feature may have difficulty being interoperably implemented in a timely manner, and marking it as such allows the WG to drop the feature if necessary when transitioning to the Proposed Rec stage, without having to publish a new Candidate Rec without the feature first.

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

If you notice any inconsistencies between this Grid Layout Module and the Flexible Box Layout Module, please report them to the CSSWG, as this is likely an error.

1. Introduction

This section is not normative.

Grid Layout is a new layout model for CSS that has powerful abilities to control the sizing and positioning of boxes and their contents. Unlike Flexible Box Layout, which is single-axis–oriented, Grid Layout is optimized for 2-dimensional layouts: those in which alignment of content is desired in both dimensions.

Representative Flex Layout Example

Representative Grid Layout Example

In addition, due to its ability to explicitly position items in the grid, Grid Layout allows dramatic transformations in visual layout structure without requiring corresponding markup changes. 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, while preserving a more ideal semantic structuring of their content across presentations.

Although many layouts can be expressed with either Grid or Flexbox, they each have their specialties. Grid enforces 2-dimensional alignment, uses a top-down approach to layout, allows explicit overlapping of items, and has more powerful spanning capabilities. Flexbox focuses on space distribution within an axis, uses a simpler bottom-up approach to layout, can use a content-size–based line-wrapping system to control its secondary axis, and relies on the underlying markup hierarchy to build more complex layouts. It is expected that both will be valuable and complementary tools for CSS authors.

1.1. Background and Motivation

Application layout example requiring horizontal and vertical alignment.

As websites evolved from simple documents into complex, interactive applications, techniques 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 into the grid areas defined by the intersections of these columns and rows. The following examples illustrate the adaptive capabilities of grid layout, and how it allows a cleaner separation of content and style.

1.1.1. Adapting Layouts to Available Space

Five grid items arranged according to content size and available space.

Growth in the grid due to an increase in available space.

Grid layout can be used to intelligently resize elements within a webpage. The adjacent figures represent a game with five major components 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:

The stats area always appears immediately under the game title.

The game board appears to the right of the stats and title.

The top of the game title and the game board should always align.

The bottom of the game board and bottom of the stats area align when the game has reached its minimum height. In all other cases the game board will stretch to take advantage of all the space available to it.

The controls are centered under the game board.

The top of the score area is aligned to the top of the controls area.

The score area is beneath the stats area.

The score area is aligned to the controls beneath the stats area.

The following grid layout example shows how an author might achieve all the sizing, placement, and alignment rules declaratively.

/** * Define the space for each grid item by declaring the grid * on the grid container . */ #grid { /** * Two columns: * 1. the first sized to content, * 2. 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 [Figure 4]) * * Three rows: * 3. the first sized to content, * 4. the middle row receives the remaining space * (but is never smaller than the minimum height * of the board or stats areas) * 5. the last sized to content. */ display : grid ; grid-template-columns : /* 1 */ auto /* 2 */ 1 fr ; grid-template-rows : /* 3 */ auto /* 4 */ 1 fr /* 5 */ auto ; } /* Specify the position of each grid item using coordinates on * the 'grid-row' and 'grid-column' properties of each grid item . */ #title { grid-column : 1 ; grid-row : 1 ; } #score { grid-column : 1 ; grid-row : 3 ; } #stats { grid-column : 1 ; grid-row : 2 ; align-self : start ; } #board { grid-column : 2 ; grid-row : 1 / span 2 ; } #controls { grid-column : 2 ; grid-row : 3 ; justify-self : center ; } < 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 >

Note: There are multiple ways to specify the structure of the grid and to position and size grid items, each optimized for different scenarios.

1.1.2. Source-Order Independence

An arrangement suitable for “portrait” orientation.

An arrangement suitable for “landscape“ orientation.

Continuing the prior example, the author also wants the game to adapt to different devices. Also, the game should optimize the placement of the components when viewed either in portrait or landscape orientation (Figures 6 and 7). 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 uses 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.

@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"; /* The way to size columns and rows can be assigned with the * grid-template-columns and grid-template-rows properties. */ grid-template-columns: auto 1fr; grid-template-rows: auto auto 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 1fr; grid-template-rows: auto 1fr auto; } } /* The grid-area property places a grid item into a named * area of the grid. */ #title { grid-area: title } #score { grid-area: score } #stats { grid-area: stats } #board { grid-area: board } #controls { grid-area: ctrls } < 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 >

Note: The reordering capabilities of grid layout intentionally affect only the visual rendering, leaving speech order and navigation based on the source order. This allows authors to manipulate the visual presentation while leaving the source order intact and optimized for non-CSS UAs and for linear models such as speech and sequential navigation.

Grid item placement and reordering must not be used as a substitute for correct source ordering, as that can ruin the accessibility of the document.

1.2. Value Definitions

This specification follows the CSS property definition conventions from [CSS2] using the value definition syntax from [CSS-VALUES-3]. Value types not defined in this specification are defined in CSS Values & Units [CSS-VALUES-3]. Combination with other CSS modules may expand the definitions of these value types.

In addition to the property-specific values listed in their definitions, all properties defined in this specification also accept the CSS-wide keywords keywords as their property value. For readability they have not been repeated explicitly.

2. Overview

This section is not normative.

Grid Layout controls the layout of its content through the use of a grid: an intersecting set of horizontal and vertical lines which create a sizing and positioning coordinate system for the grid container’s contents. Grid Layout features

Grid containers can be nested or mixed with flex containers as necessary to create more complex layouts.

2.1. Declaring the Grid

The tracks (rows and columns) of the grid are declared and sized either explicitly through the explicit grid properties or are implicitly created when items are placed outside the explicit grid. The grid shorthand and its sub-properties define the parameters of the grid. § 7 Defining the Grid

The following declares a grid with four named areas: H , A , B , and F . The first column is sized to fit its contents (auto), and the second column takes up the remaining space (1fr). Rows default to auto (content-based) sizing; the last row is given a fixed size of 30px . main { grid: "H H " "A B " "F F " 30px / auto 1fr; }

, , , and . The first column is sized to fit its contents (auto), and the second column takes up the remaining space (1fr). Rows default to (content-based) sizing; the last row is given a fixed size of . The following declares a grid with as many rows of at least 5em as will fit in the height of the grid container ( 100vh ). The grid has no explicit columns; instead columns are added as content is added, the resulting column widths are equalized (1fr). Since content overflowing to the right won’t print, an alternate layout for printing adds rows instead. main { grid: repeat(auto-fill, 5em) / auto-flow 1fr; height: 100vh; } @media print { main { grid: auto-flow 1fr / repeat(auto-fill, 5em); } }

as will fit in the height of the grid container ( ). The grid has no explicit columns; instead columns are added as content is added, the resulting column widths are equalized (1fr). Since content overflowing to the right won’t print, an alternate layout for printing adds rows instead. The following declares a grid with 5 evenly-sized columns and three rows, with the middle row taking up all remaining space (and at least enough to fit its contents). main { grid: auto 1fr auto / repeat(5, 1fr); min-height: 100vh; } Below are some examples of grid declarations:

2.2. Placing Items

The contents of the grid container are organized into individual grid items (analogous to flex items), which are then assigned to predefined areas in the grid. They can be explicitly placed using coordinates through the grid-placement properties or implicitly placed into empty areas using auto-placement. § 8 Placing Grid Items

grid-area: a; /* Place into named grid area “a” */ grid-area: auto; /* Auto-place into next empty area */ grid-area: 2 / 4; /* Place into row 2, column 4 */ grid-area: 1 / 3 / -1; /* Place into column 3, span all rows */ grid-area: header-start / sidebar-start / footer-end / sidebar-end; /* Place using named lines */ Below are some examples of grid placement declarations using the grid-area shorthand: These are equivalent to the following grid-row + grid-column declarations: grid-row: a; grid-column: a; grid-row: auto; grid-column: auto; grid-row: 2; grid-column: 4; grid-row: 1 / -1; grid-column: 3; grid-row: header-start / footer-end; grid-column: sidebar-start / sidebar-end; They can further be decomposed into the grid-row-start/grid-row-end/grid-column-start/grid-column-end longhands, e.g. grid-area: a; /* Equivalent to grid-row-start: a; grid-column-start: a; grid-row-end: a; grid-column-end: a; */ grid-area: 1 / 3 / -1; /* Equivalent to grid-row-start: 1; grid-column-start: 3; grid-row-end: -1; grid-column-end: auto; */

2.3. Sizing the Grid

Once the grid items have been placed, the sizes of the grid tracks (rows and columns) are calculated, accounting for the sizes of their contents and/or available space as specified in the grid definition.

The resulting sized grid is aligned within the grid container according to the grid container’s align-content and justify-content properties. § 10 Alignment and Spacing

main { grid: auto-flow 1fr / repeat(auto-fill, 5em); min-height: 100vh; justify-content: space-between; align-content: safe center; } The following example justifies all columns by distributing any extra space among them, and centers the grid in the grid container when it is smaller than 100vh.

Finally each grid item is sized and aligned within its assigned grid area, as specified by its own sizing [CSS2] and alignment properties [CSS-ALIGN-3].

3. 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, and an orthogonal set defining rows along the inline axis. [CSS3-WRITING-MODES]

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

3.1. 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.

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

3.2. 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. Adjacent grid tracks can be separated by gutters but are otherwise packed tightly.

A grid cell is the intersection of a grid row and a grid column. It is the smallest unit of the grid that can be referenced when positioning grid items.

grid container is 200px, then the second column is 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 . #grid { display: grid; grid-template-columns: 150px 1fr; /* two columns */ grid-template-rows: 50px 1fr 50px; /* three rows */ } 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 theis 200px, then the second column is 50px wide. If the used width of theis 100px, then the second column is 0px and any content positioned in the column will overflow the

3.3. Grid Areas

A grid area is the logical space used to lay out one or more grid items. A grid area consists of one or more adjacent grid cells. 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.

/* 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; }

A grid item’s grid area forms the containing block into which it is laid out. Grid items placed into the same grid area do not directly affect each other’s layout. Indirectly, however, a grid item occupying a grid track with an intrinsic sizing function can affect the size of that track (and thus the positions of its bounding grid lines), which in turn can affect the position or size of another grid item.

4. Reordering and Accessibility

Grid layout gives authors great powers of rearrangement over the document. However, these are not a substitute for correct ordering of the document source. The order property and grid placement do not affect ordering in non-visual media (such as speech). Likewise, rearranging grid items visually does not affect the default traversal order of sequential navigation modes (such as cycling through links, see e.g. tabindex [HTML]).

Authors must use order and the grid-placement properties only for visual, not logical, reordering of content. Style sheets that use these features to perform logical reordering are non-conforming.

Note: This is so that non-visual media and non-CSS UAs, which typically present content linearly, can rely on a logical source order, while grid layout’s placement and ordering features are used to tailor the visual arrangement. (Since visual perception is two-dimensional and non-linear, the desired visual order is not always equivalent to the desired reading order.)

<!DOCTYPE html> < header > ... </ header > < article > ... </ article > < nav > ... </ nav > < aside > ... </ aside > < footer > ... </ footer > Many web pages have a similar shape in the markup, with a header on top, a footer on bottom, and then a content area and one or two additional columns in the middle. Generally, it’s desirable that the content come first in the page’s source code, before the additional columns. However, this makes many common designs, such as simply having the additional columns on the left and the content area on the right, difficult to achieve. This has been addressed in many ways over the years, often going by the name "Holy Grail Layout" when there are two additional columns. Grid Layout makes this example trivial. For example, take the following sketch of a page’s code and desired layout: This layout can be easily achieved with grid layout: body { display : grid ; grid : "h h h" "a b c" "f f f" ; grid-template-columns : auto 1 fr 20 % ; } article { grid-area : b ; min-width : 12 em ; } nav { grid-area : a ; /* auto min-width */ } aside { grid-area : c ; min-width : 12 em ; } As an added bonus, the columns will all be equal-height by default, and the main content will be as wide as necessary to fill the screen. Additionally, this can then be combined with media queries to switch to an all-vertical layout on narrow screens: @media all and ( max-width : 60em) { /* Too narrow to support three columns */ main { display: block; } }

In order to preserve the author’s intended ordering in all presentation modes, authoring tools—including WYSIWYG editors as well as Web-based authoring aids— must reorder the underlying document source and not use order or grid-placement properties to perform reordering unless the author has explicitly indicated that the underlying document order (which determines speech and navigation order) should be out-of-sync with the visual order.

For example, a tool might offer both drag-and-drop arrangement of grid items as well as handling of media queries for alternate layouts per screen size range. Since most of the time, reordering should affect all screen ranges as well as navigation and speech order, the tool would match the resulting drag-and-drop visual arrangement by simultaneously reordering the DOM layer. In some cases, however, the author may want different visual arrangements per screen size. The tool could offer this functionality by using the grid-placement properties together with media queries, but also tie the smallest screen size’s arrangement to the underlying DOM order (since this is most likely to be a logical linear presentation order) while using grid-placement properties to rearrange the visual presentation in other size ranges. This tool would be conformant, whereas a tool that only ever used the grid-placement properties to handle drag-and-drop grid rearrangement (however convenient it might be to implement it that way) would be non-conformant.

5. Grid Containers

grid This value causes an element to generate a grid container box that is block-level when placed in flow layout. inline-grid This value causes an element to generate an grid container box that is inline-level when placed in flow layout.

A grid container establishes an independent grid formatting context for its contents. This is the same as establishing an independent 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. The contents of a grid container are laid out into a grid, with grid lines forming the boundaries of each grid items’ containing block.

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:

float and clear have no effect on a grid item. However, the float property still affects the computed value of display on children of a grid container, as this occurs before grid items are determined.

property still affects the computed value of display on children of a grid container, as this occurs before are determined. vertical-align has no effect on a grid item.

the ::first-line and ::first-letter pseudo-elements do not apply to grid containers, and grid containers do not contribute a first formatted line or first letter to their ancestors.

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.

5.2. Sizing Grid Containers

Note see [CSS-SIZING-3] for a definition of the terms in this section.

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 a block box that establishes a formatting context, with an auto inline size calculated as for non-replaced 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 probably define this, but it isn’t written yet.

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

5.3. Scrollable Grid Overflow

The overflow property applies to grid containers.

Just as it is included in intrinsic sizing (see above), the grid is also included in a grid container’s scrollable overflow region.

Note: Beware the interaction with padding when the grid container is a scroll container: additional padding is defined to be added to the scrollable overflow rectangle as needed to enable place-content: end alignment of scrollable content. See CSS Overflow 3 §2.2 Scrollable Overflow

5.4. Limiting Large Grids

Since memory is limited, UAs may clamp the possible size of the implicit grid to be within a UA-defined limit (which should accommodate lines at in the range [-10000, 10000]), dropping all lines outside that limit. If a grid item is placed outside this limit, its grid area must be clamped to within this limited grid.

To clamp a grid area :

If the grid area would span outside the limited grid, its span is clamped to the last line of the limited grid.

If the grid area would be placed completely outside the limited grid, its span must be truncated to 1 and the area repositioned into the last grid track on that side of the grid.

.grid-item { grid-row : 500 / 1500 ; grid-column : 2000 / 3000 ; } For example, if a UA only supported grids with at most 1000 tracks in each dimension, the following placement properties: Would end up being equivalent to: .grid-item { grid-row : 500 / 1001 ; grid-column : 1000 / 1001 ; }

6. Grid Items

Loosely speaking, the grid items of a grid container are boxes representing its in-flow contents.

Each in-flow child of a grid container becomes a grid item, and each contiguous sequence of child text runs is wrapped in an anonymous block container grid item. However, if the entire sequence of child text runs contains only white space (i.e. characters that can be affected by the white-space property) it is instead not rendered (just as if its text nodes were display:none).

Note: inter-element white space disappears: it does not become its own grid item, even though inter-element text does get wrapped in an anonymous grid item.

Note: The box of a anonymous item is unstyleable, since there is no element to assign style rules to. Its contents will however inherit styles (such as font settings) from the grid container.

6.1. Grid Item Display

A grid item establishes an independent formatting context for its contents. 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.

If the computed display value of an element’s nearest ancestor element (skipping display:contents ancestors) is grid or inline-grid, the element’s own display value is blockified. (See CSS2.1§9.7 [CSS2] and CSS Display 3 §2.7 Automatic Box Type Transformations for details on this type of display value conversion.)

Note: Blockification still occurs even when the grid or inline-grid element does not end up generating a grid container box, e.g. when it is replaced or in a display: none subtree.

Note: Some values of display normally trigger the creation of anonymous boxes around the original box. If such a box is a grid item, it is blockified first, and so anonymous box creation will not happen. For example, two contiguous grid items with display: table-cell will become two separate display: block grid items, instead of being wrapped into a single anonymous table.

6.2. Grid Item Sizing

A grid item is sized within the containing block defined by its grid area.

Grid item calculations for auto widths and heights vary by their self-alignment values:

Summary of automatic sizing behavior of grid items Alignment Non-replaced Element Size Replaced Element Size normal Fill grid area Use intrinsic size stretch Fill grid area Fill grid area start/ center fit-content sizing (like floats) Use intrinsic size The following informative table summarizes the automatic sizing of grid items:

Note: The auto value of min-width and min-height affects track sizing in the relevant axis similar to how it affects the main size of a flex item. See § 6.6 Automatic Minimum Size of Grid Items.

6.3. Reordered Grid Items: the order property

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

As with reordering flex items, the order property must only be used when the visual order needs to be out-of-sync with the speech and navigation order; otherwise the underlying document source should be reordered instead. See CSS Flexbox 1 §5.4.1 Reordering and Accessibility in [CSS-FLEXBOX-1].

6.4. Grid Item Margins and Paddings

As adjacent grid items are independently contained within the containing block formed by their grid areas, the margins of adjacent grid items do not collapse.

Percentage margins and paddings on grid items, like those on block boxes, are resolved against the inline size of their containing block, e.g. left/right/top/bottom percentages all resolve against their containing block’s width in horizontal writing modes.

Auto margins expand to absorb extra space in the corresponding dimension, and can therefore be used for alignment. See § 10.2 Aligning with auto margins

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 [CSS2], 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 (behaving exactly as if position were relative). 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.

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> 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.

6.6. Automatic Minimum Size of Grid Items

Note: Much of the sizing terminology used in this section (and throughout the rest of the specification) is defined in CSS Intrinsic and Extrinsic Sizing [CSS-SIZING-3].

To provide a more reasonable default minimum size for grid items, the used value of its automatic minimum size in a given axis is the content-based minimum size if all of the following are true:

it is not a scroll container

it spans at least one track in that axis whose min track sizing function is auto

if it spans more than one track in that axis, none of those tracks are flexible

Otherwise, the automatic minimum size is zero, as usual.

The content-based minimum size for a grid item in a given dimension is its specified size suggestion if it exists, otherwise its transferred size suggestion if that exists, else its content size suggestion, see below. However, if in a given dimension the grid item spans only grid tracks that have a fixed max track sizing function, then its specified size suggestion and content size suggestion in that dimension (and its input from this dimension to the transferred size suggestion in the opposite dimension) are further clamped to less than or equal to the stretch fit into the grid area’s maximum size in that dimension, as represented by the sum of those grid tracks’ max track sizing functions plus any intervening fixed gutters.

Note: The argument to fit-content() does not clamp the content-based minimum size in the same way as a fixed max track sizing function.

The content size suggestion, specified size suggestion, and transferred size suggestion used in this calculation account for the relevant min/max/preferred size properties so that the content-based minimum size does not interfere with any author-provided constraints, and are defined below:

For the purpose of calculating an intrinsic size of the box (e.g. the box’s min-content size), a content-based minimum size causes the box’s size in that axis to become indefinite (even if e.g. its width property specifies a definite size). Note this means that percentages calculated against this size will behave as auto.

Nonetheless, although this may require an additional layout pass to re-resolve percentages in some cases, this value (like the min-content, max-content, and fit-content values defined in [CSS-SIZING-3]) does not prevent the resolution of percentage sizes within the item.

Note that while a content-based minimum size is often appropriate, and helps prevent content from overlapping or spilling outside its container, in some cases it is not: In particular, if grid layout is being used for a major content area of a document, it is better to set an explicit font-relative minimum width such as min-width: 12em. A content-based minimum width could result in a large table or large image stretching the size of the entire content area, potentially into an overflow zone, and thereby making lines of text needlessly long and hard to read. Note also, when content-based sizing is used on an item with large amounts of content, the layout engine must traverse all of this content before finding its minimum size, whereas if the author sets an explicit minimum, this is not necessary. (For items with small amounts of content, however, this traversal is trivial and therefore not a performance concern.)

7. Defining the Grid

7.1. 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 by specifying its explicit grid tracks . The final grid may end up larger due to grid items placed outside the explicit grid; in this case implicit tracks will be created, these implicit tracks will be 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. If these properties don’t define any explicit tracks the explicit grid still contains one grid line in each axis.

Numeric indexes in the grid-placement properties count from the edges of the explicit grid. Positive indexes count from the start side (starting from 1 for the start-most explicit line), while negative indexes count from the end side (starting from -1 for the end-most explicit line).

The grid and grid-template properties are shorthands that can be used to set all three explicit grid properties (grid-template-rows, grid-template-columns, and grid-template-areas) at the same time. The grid shorthand also resets properties controlling the implicit grid, whereas the grid-template property leaves them unchanged.

These properties specify, as a space-separated track list , the line names and track sizing functions of the grid. 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.

Values have the following meanings:

The syntax of a track list is:

Where the component values are defined as follows…

7.2.1. Track Sizes

/* 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); Additional examples of valid grid track definitions:

Note: The size of the grid is not purely the sum of the track sizes, as row-gap, column-gap and justify-content, align-content can add additional space between tracks.

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

#grid { display: grid; grid-template-columns: [first nav-start] 150px [main-start] 1fr [last]; grid-template-rows: [first header-start] 50px [main-start] 1fr [footer-start] 50px [last]; } Named Grid Lines. 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.

A line name cannot be span or auto, i.e. the <custom-ident> in the <line-names> production excludes the keywords span and auto.

7.2.3. Repeating Rows and Columns: the repeat() notation

The repeat() notation represents a repeated fragment of the track list, allowing a large number of columns or rows that exhibit a recurring pattern to be written in a more compact form.

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; /* same as above, except easier to write */ grid-template-columns: repeat(4, 10px [col-start] 250px [col-end]) 10px; This example shows two equivalent ways of writing the same grid definition. Both declarations produce four “main” columns, each 250px wide, surrounded by 10px “gutter” columns.

The generic form of the repeat() syntax is, approximately,

The first argument specifies the number of repetitions. The second argument is a track list, which is repeated that number of times. However, there are some restrictions:

The repeat() notation can’t be nested.

Automatic repetitions (auto-fill or auto-fit) cannot be combined with intrinsic or flexible sizes.

Thus the precise syntax of the repeat() notation has several forms:

The <track-repeat> variant can represent the repetition of any <track-size>, but is limited to a fixed number of repetitions.

The <auto-repeat> variant can repeat automatically to fill a space, but requires definite track sizes so that the number of repetitions can be calculated. It can only appear once in the track list, but the same track list can also contain <fixed-repeat>s.

If a 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].

When auto-fill is given as the repetition number, if the grid container has a definite size or max size in the relevant axis, then the number of repetitions is the largest possible positive integer that does not cause the grid to overflow the content box of its grid container (treating each track as its max track sizing function if that is definite or as its minimum track sizing function otherwise, flooring the max track sizing function by the min track sizing function if both are definite, and taking gap into account); if any number of repetitions would overflow, then 1 repetition. Otherwise, if the grid container has a definite min size in the relevant axis, the number of repetitions is the smallest possible positive integer that fulfills that minimum requirement. Otherwise, the specified track list repeats only once.

body { display: grid; grid-template-columns: repeat(auto-fill, minmax(25ch, 1fr)); } For example, the following code will create as many 25-character columns as will fit into the window width. If there is any remaining space, it will be distributed among the 25-character columns.

The auto-fit keyword behaves the same as auto-fill, except that after grid item placement any empty repeated tracks are collapsed. An empty track is one with no in-flow grid items placed into or spanning across it. (This can result in all tracks being collapsed, if they’re all empty.)

A collapsed track is treated as having a fixed track sizing function of 0px, and the gutters on either side of it— including any space allotted through distributed alignment— collapse.

For the purpose of finding the number of auto-repeated tracks, the UA must floor the track size to a UA-specified value to avoid division by zero. It is suggested that this floor be 1px.

If two repeat() notations that have the same first argument (repetition count) and the same number of tracks in their second argument (the track listing), they are combined by combining each component of their computed track lists by computed value (just like combining a top-level track list). They otherwise combine discretely.

7.2.4. Flexible Lengths: the fr unit

A flexible length or <flex> is a dimension with the fr unit, which represents a fraction of the leftover space in the grid container. Tracks sized with fr units are called flexible tracks as they flex in response to leftover space similar to how flex items with a zero base size fill space in a flex container.

The distribution of leftover 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 leftover space, which is then divided among the flex-sized rows and columns in proportion to their flex factor.

Each column or row’s share of the leftover space can be computed as the column or row’s <flex> * <leftover space> / <sum of all flex factors> .

<flex> values between 0fr and 1fr have a somewhat special behavior: when the sum of the flex factors is less than 1, they will take up less than 100% of the leftover space. A track’s <flex> value is effectively a request for some proportion of the leftover space, with 1fr meaning “100% of the leftover space”; then if the tracks in that axis are requesting more than 100% in total, the requests are rebalanced to keep the same ratio but use up exactly 100% of it. However, if the tracks request less than the full amount (such as three tracks that are each .25fr) then they’ll each get exactly what they request (25% of the leftover space to each, with the final 25% left unfilled). See § 11.7 Expand Flexible Tracks for the exact details of how leftover space is distributed. This pattern is required for continuous behavior as fr values approach zero (which means the tracks wants none of the leftover space). Without this, a 1fr track would take all of the leftover space; but so would a 0.1fr track, and a 0.01fr track, etc., until finally the value is small enough to underflow to zero and the track suddenly takes up none of the leftover space. With this behavior, the track instead gradually takes less of the leftover space as its flex factor shrinks below 1fr, smoothly transitioning to taking none of the leftover space at zero. Unless this “partial fill” behavior is specifically what’s desired, authors should stick to values ≥ 1; for example, using 1fr and 2fr is usually better than using .33fr and .67fr, as they’re more likely to behave as intended if tracks are added or removed.

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.

Note: <flex> values are not <length>s (nor are they compatible with <length>s, like some <percentage> values), so they cannot be represented in or combined with other unit types in calc() expressions.

7.2.5. Computed Value of a Track Listing

A computed track list is a list alternating between line name sets and track sections, with the first and last items being line name sets.

A line name set is a (potentially empty) set of identifiers representing line names.

A track section is either:

a minmax() functional notation representing a single track’s size, with each <length-percentage> computed

a repeat() functional notation representing a repeated track list section, with its <integer> computed and its <track-list> represented as a computed track list

7.2.6. Resolved Value of a Track Listing

The grid-template-rows and grid-template-columns properties are resolved value special case properties. [CSSOM]

When an element generates a grid container box, the resolved value of its grid-template-rows or grid-template-columns property is the used value, serialized with:

Every track listed individually, whether implicitly or explicitly created, without using the repeat() notation.

Every track size given as a length in pixels, regardless of sizing function.

Adjacent line names collapsed into a single bracketed set.

grid-template-rows and const s = getComputedStyle ( gridEl ); gridEl . style . gridTemplateRows = s . gridTemplateRows ; // Code like this should be a no-op, // but if there are any implicit rows, // this will convert them into explicit rows, // possibly changing how grid items are positioned // and altering the overall size of the grid! The first bullet point of the above list means that implicit tracks get serialized as part of grid-template-rows /etc., despite the fact that an author cannot actually specify implicit track sizes in those properties! Soand grid-template-columns values might not round-trip correctly: This is an accidental property of an early implementation that leaked into later implementations without much thought given to it. We intend to remove it from the spec, but not until after we’ve defined a CSSOM API for getting information about implicit tracks, as currently this is the only way to get that information and a number of pages rely on that.

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

< style > # grid { width : 500 px ; grid-template-columns : [ a ] auto [ b ] minmax ( min - content , 1 fr ) [ b c d ] repeat ( 2 , [ e ] 40 px ) 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 ). gridTemplateColumns ; // [a] 50px [b] 320px [b c d e] 40px [e] 40px 0px 0px 0px 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.

The CSS Working Group is considering whether to also return used values for the grid-placement properties and is looking for feedback, especially from implementors. See discussion.

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:

head ), navigational content ( nav ), footer content ( foot ), and main content ( main ). Accordingly, the template creates three rows and two columns, with four head area spans both columns and the first row of the grid. #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; } In this example, the grid-template-areas property is used to create a page layout where areas are defined for header content (), navigational content (), footer content (), and main content (). Accordingly, the template creates three rows and two columns, with four named grid areas . Thearea spans both columns and the first row of the grid.

7.3.1. Serialization Of Template Strings

When serializing either the specified or computed value of a <string> value of grid-template-areas, each null cell token is serialized as a single "." (U+002E FULL STOP), and consecutive cell tokens are separated by a single space (U+0020 SPACE), with all other white space elided.

7.3.2. Implicitly-Assigned Line Names

The grid-template-areas property generates implicitly-assigned line names from the named grid areas in the template. For each named grid area foo , four implicitly-assigned line names 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 implicitly-assigned line names behave just like any other line names, except that they do not appear in the value of grid-template-rows/grid-template-columns. Even if an explicitly-assigned line name with the same name is defined, the implicitly-assigned line names are just more lines with the same name.

7.3.3. Implicitly-Named Areas

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

7.4. Explicit Grid Shorthand: the grid-template property

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). <'grid-template-rows'> / <'grid-template-columns'> Sets grid-template-rows and grid-template-columns to the specified values, respectively, and sets grid-template-areas to none. grid-template: auto 1fr / auto 1fr auto; is equivalent to grid-template-rows: auto 1fr; grid-template-columns: auto 1fr auto; grid-template-areas: none; [ <line-names>? <string> <track-size>? <line-names> ? ]+ [ / <explicit-track-list> ]? Sets grid-template-areas to the strings listed.

Sets grid-template-rows to the <track-size>s following each string (filling in auto for any missing sizes), and splicing in the named lines defined before/after each size.

Sets grid-template-columns to the track listing specified after the slash (or none, if not specified). This syntax allows the author to align track names and sizes inline with their respective grid areas. grid-template: [header-top] "a a a" [header-bottom] [main-top] "b b b" 1fr [main-bottom] / auto 1fr auto; is equivalent to grid-template-areas: "a a a" "b b b"; grid-template-rows: [header-top] auto [header-bottom main-top] 1fr [main-bottom]; grid-template-columns: auto 1fr auto; and creates the following grid: Three columns, sized auto, 1fr , and auto , respectively

, and , respectively Two rows sized as auto and 1fr , respectively.

, respectively. A line named both “header-top” and “a-start” at the top, a line with four names— “header-bottom”, “main-top”, “a-end”, and “b-start”— in the middle, a line named “main-bottom” and “b-end” at the bottom. A line named “a-start” and “b-start” on the left edge, and a line named “a-end” and “b-end” on the right edge.

The grid created by the declarations above. (The “a/b-start/end” names are implicitly assigned by the named grid areas.) Note: Note that the repeat() function isn’t allowed in these track listings, as the tracks are intended to visually line up one-to-one with the rows/columns in the “ASCII art”.

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.

7.5. The Implicit Grid

The grid-template-rows, grid-template-columns, and grid-template-areas properties define a fixed number of tracks that form the explicit grid. When grid items are positioned outside of these bounds, the grid container generates implicit grid tracks by adding implicit grid lines to the grid. These lines together with the explicit grid form the implicit grid . The grid-auto-rows and grid-auto-columns properties size these implicit grid tracks, as well as any explicit grid tracks created by grid-template-areas but not explicitly sized by grid-template-rows or grid-template-columns

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.

The grid shorthand property can set the implicit grid properties (grid-auto-flow, grid-auto-rows, and grid-auto-columns) together with the explicit grid properties in a single declaration.

The grid-auto-columns and grid-auto-rows properties specify the size of tracks not assigned a size by grid-template-rows or grid-template-columns. If multiple track sizes are given, the pattern is repeated as necessary to find the size of the affected tracks. The first track after the last explicitly-sized track receives the first specified size, and so on forwards; and the last implicit grid track before the explicit grid receives the last specified size, and so on backwards.

Note: If a grid item is positioned into a row or column that is not explicitly declared by grid-template-rows/grid-template-columns and/or grid-template-areas, 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.

< style > # grid { display : grid ; grid-template-columns : 20 px ; grid-auto-columns : 40 px ; grid-template-rows : 20 px ; grid-auto-rows : 40 px ; } # A { grid-column : 1 ; grid-row : 1 ; } # B { grid-column : 2 ; grid-row : 1 ; } # C { grid-column : 1 ; grid-row : 2 ; } # D { grid-column : 2 ; grid-row : 2 ; } </ 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 > A 2×2 grid with one explicit 20px×20px grid cell in the first row+column and three additional cells resulting from the implicit 40px column and row generated to hold the additional grid items.

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

Grid items that aren’t explicitly placed are automatically placed into an unoccupied space in the grid container by the auto-placement algorithm. grid-auto-flow controls how the auto-placement algorithm works, specifying exactly how auto-placed items get flowed into the grid. See § 8.5 Grid Item Placement Algorithm for details on precisely how the auto-placement algorithm works.

row The auto-placement algorithm places items by filling each row in turn, adding new rows as necessary. If neither row nor column is provided, row is assumed. 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 earlier in the grid if smaller items come up later. This may cause items to appear out-of-order, when doing so would fill in holes left by larger items. If omitted, a “sparse” algorithm is used, where the placement algorithm only ever moves “forward” in the grid when placing items, never backtracking to fill holes. This ensures that all of the auto-placed items appear “in order”, even if this leaves holes that could have been filled by later items.

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.

<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 dense; } 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-block { /* 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 inline 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-block"> <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> 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

7.8. Grid Definition Shorthand: the grid property

The grid property is a shorthand that sets all of the explicit grid properties (grid-template-rows, grid-template-columns, and grid-template-areas), and all the implicit grid properties (grid-auto-rows, grid-auto-columns, and grid-auto-flow), in a single declaration. (It does not reset the gutter properties.) Its syntax matches grid-template, plus an additional syntax form for defining auto-flow grids:

<'grid-template-rows'> / [ auto-flow && dense? ] <'grid-auto-columns'>? [ auto-flow && dense? ] <'grid-auto-rows'>? / <'grid-template-columns'> Sets up auto-flow, by setting the tracks in one axis explicitly (setting either grid-template-rows or grid-template-columns as specified, and setting the other to none), and specifying how to auto-repeat the tracks in the other axis (setting either grid-auto-rows or grid-auto-columns as specified, and setting the other to auto ). grid-auto-flow is also set to either row or column accordingly, with dense if it’s specified. All other grid sub-properties are reset 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.

8. Placing Grid Items

Every grid item is associated with a grid area, a rectangular set of adjacent grid cells that the grid item occupies. This grid area defines the containing block for the grid item within which the self-alignment properties (justify-self and align-self) determine their actual position. The cells that a grid item occupies also influence the sizing of the grid’s rows and columns, defined in § 11 Grid Sizing.

The location of a grid item’s grid area within the grid is defined by its placement , which consists of a grid position and a grid span:

grid position The grid item’s location in the grid in each axis. 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 in each axis. In Level 1, a grid item ’s grid span is always definite , defaulting to 1 in each axis if it can’t be otherwise determined for that axis.

The grid-placement properties — the longhands grid-row-start, grid-row-end, grid-column-start, grid-column-end, and their shorthands grid-row, grid-column, and grid-area— allow 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. Automatic No lines explicitly specified N/A

8.1. Common Patterns for Grid Placement

This section is informative.

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

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 lines 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 - start at the 5th line named "text", then span across two more "text" lines, to the 7th. */ }

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 searches 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.

8.2. Grid Item Placement vs. Source Order

“With great power comes great responsibility.”

The abilities of the grid-placement properties allow content to be freely arranged and reordered within the grid, such that the visual presentation can be largely disjoint from the underlying document source order. These abilities allow the author great freedom in tailoring the rendering to different devices and modes of presentation e.g. using media queries. However they are not a substitute for correct source ordering.

Correct source order is important for speech, for sequential navigation (such as keyboard navigation), and non-CSS UAs such as search engines, tactile browsers, etc. Grid placement only affects the visual presentation! This allows authors to optimize the document source for non-CSS/non-visual interaction modes, and use grid placement techniques to further manipulate the visual presentation so as to leave that source order intact.

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:

In all the above productions, the <custom-ident> additionally excludes the keywords span and auto.

1 2 3 4 5 6 7 8 9 +--+--+--+--+--+--+--+--+ | | | | | | | | | A B C A B C A B C | | | | | | | | | +--+--+--+--+--+--+--+--+ Given a single-row, 8-column grid and the following 9 named lines: 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 */

8.3.1. Grid Placement Conflict Handling

If the placement for a grid item contains two lines, and the start line is further end-ward than the end line, swap the two lines. If the start line is equal to the end line, remove the end line.

If the placement contains two spans, remove the one contributed by the end grid-placement property.

If the placement contains only a span for a named line, replace it with a span of 1.

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.

The grid-area property is a shorthand for grid-row-start, grid-column-start, grid-row-end and grid-column-end.

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.

8.5. Grid Item Placement Algorithm

The following grid item placement algorithm resolves automatic positions of grid items into definite positions, ensuring that every grid item has a well-defined grid area to lay out into. (Grid spans need no special resolution; if they’re not explicitly specified, they default to 1.)

Note: This algorithm can result in the creation of new rows or columns in the implicit grid, if there is no room in the explicit grid to place an auto-positioned grid item.

Every grid cell (in both the explicit and implicit grids) can be occupied or unoccupied . A cell is occupied if it’s covered by the grid area of a grid item with a definite grid position; otherwise, the cell is unoccupied. A cell’s occupied/unoccupied status can change during this algorithm.

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

Note: The auto-placement algorithm works with the grid items in order-modified document order, not their original document order.

9. Absolute Positioning

9.1. With a Grid Container as Containing Block

If an absolutely positioned element’s containing block is generated by a grid container, the containing block corresponds to the grid area determined by its grid-placement properties. The offset properties (top/right/bottom/left) then indicate offsets inwards from the corresponding edges of this containing block, as normal.

Note: 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.

Instead of auto-placement, an auto value for a grid-placement property contributes a special line to the placement whose position is that of the corresponding padding edge of the grid container (the padding edge of the scrollable area, if the grid container overflows). These lines become the first and last lines (0th and -0th) of the augmented grid used for positioning absolutely-positioned items.

Note: Thus, by default, the absolutely-positioned box’s containing block will correspond to the padding edges of the grid container, as it does for block containers.

Absolute positioning occurs after layout of the grid and its in-flow contents, and does not contribute to the sizing of any grid tracks or affect the size/configuration of the grid in any way. If a grid-placement property refers to a non-existent line either by explicitly specifying such a line or by spanning outside of the existing implicit grid, it is instead treated as specifying auto (instead of creating new implicit grid lines).

Note: Remember that implicit lines are assumed to have all line names, so a referenced line might exist even though it is not explicitly named.

If the placement only contains a grid span, replace it with the two auto lines in that axis. (This happens when both grid-placement properties in an axis contributed a span originally, and § 8.3.1 Grid Placement Conflict Handling caused the second span to be ignored.)

9.2. With a Grid Container as Parent

An absolutely-positioned child of a grid container is out-of-flow and not a grid item, and so does not affect the placement of other items or the sizing of the grid.

The static position [CSS2] of an absolutely-positioned child of a grid container is determined as if it were the sole grid item in a grid area whose edges coincide with the content edges of the grid container. However, if the grid container parent is also the generator of the absolutely positioned element’s containing block, instead use the grid area determined in § 9.1 With a Grid Container as Containing Block.

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.

10. Alignment and Spacing

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 what margins can do in block layout. Grid items also respect the box alignment properties from the CSS Box Alignment Module [CSS-ALIGN-3], which allow easy keyword-based alignment of items in both the rows and columns.

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.

The row-gap and column-gap properties (and their gap shorthand), when specified on a grid container, define the gutters between grid rows and grid columns. Their syntax is defined in CSS Box Alignment 3 §8 Gaps Between Boxes.

The effect of these properties is as though the affected grid lines acquired thickness: the grid track between two grid lines is the space between the gutters that represent them. For the purpose of track sizing, each gutter is treated as an extra, empty, fixed-size track of the specified size, which is spanned by any grid items that span across its corresponding grid line.

Note: Additional spacing may be added between tracks due to justify-content/align-content. See § 11.1 Grid Sizing Algorithm. This space effectively increases the size of the gutters.

If a grid is fragmented between tracks, the gutter spacing between those tracks must be suppressed. Note that gutters are suppressed even after forced breaks, unlike margins.

Gutters only appear between tracks of the implicit grid; there is no gutter before the first track or after the last track. (In particular, there is no gutter between the first/last track of the implicit grid and the “auto” lines in the augmented grid.)

When a collapsed track’s gutters collapse , they coincide exactly— the two gutters overlap so that their start and end edges coincide. If one side of a collapsed track does not have a gutter (e.g. if it is the first or last track of the implicit grid), then collapsing its gutters results in no gutter on either “side” of the collapsed track.

10.2. Aligning with auto margins

This section is non-normative. The normative definition of how margins affect grid items is in § 11 Grid Sizing.

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

During calculations of grid track sizes, auto margins are treated as 0 .

. auto margins absorb positive free space prior to alignment via the box alignment properties.

margins absorb positive free space prior to alignment via the box alignment properties. Overflowing elements ignore their auto margins and overflow as specified by their box alignment 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 [CSS-ALIGN-3].

If baseline alignment is specified on a grid item whose size in that axis depends on the size of an intrinsically-sized track (whose size is therefore dependent on both the item’s size and baseline alignment, creating a cyclic dependency), that item does not participate in baseline alignment, and instead uses its fallback alignment as if that were originally specified. For this purpose, <flex> track sizes count as “intrinsically-sized” when the grid container has an indefinite size in the relevant axis.

Note: Whether the fallback alignment is used or not does not change over the course of layout: if a cycle exists, it exists.

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 [CSS-ALIGN-3].

If baseline alignment is specified on a grid item whose size in that axis depends on the size of an intrinsically-sized track (whose size is therefore dependent on both the item’s size and baseline alignment, creating a cyclic dependency), that item does not participate in baseline alignment, and instead uses its fallback alignment as if that were originally specified. For this purpose, <flex> track sizes count as “intrinsically-sized” when the grid container has an indefinite size in the relevant axis.

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 tracks are aligned within the content box according to the justify-content and align-content properties on the grid container.

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

If there are no grid tracks (the explicit grid is empty, and no tracks were created in the implicit grid), the sole grid line in each axis is aligned with the start edge of the grid container.

Note that certain values of justify-content and align-content can cause the tracks to be spaced apart (space-around, space-between, space-evenly) or to be resized (stretch). If the grid is fragmented between tracks, any such additional spacing between those tracks must be suppressed.

.wrapper { display: grid; /* 3-row / 4-column grid container */ grid: repeat(3, auto) / repeat(4, auto); gap: 10px; align-content: space-around; justify-content: space-between; } .item1 { grid-column: 1 / 5; } .item2 { grid-column: 1 / 3; grid-row: 2 / 4; } .item3 { grid-column: 3 / 5; } /* last two items auto-place into the last two grid cells */ Grid before alignment Grid after alignment For example, in the following grid, the spanning item’s grid area is increased to accommodate the extra space assigned to the gutters due to alignment: Note that alignment (unlike gap spacing) happens after the grid tracks are sized, so if the track sizes are determined by the contents of the spanned item, it will gain excess space in the alignment stage to accommodate the alignment spacing.

10.6. Grid Container Baselines

The first (last) baselines of a grid container are determined as follows:

Grid-modified document order (grid order) is the order in which grid items are encountered when traversing the grid’s grid cells. 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. [CSS2]

See CSS Writing Modes 3 §4.1 Introduction to Baselines and CSS Box Alignment 3 §9 Baseline Alignment Details for more information on baselines.

11. Grid Sizing

This section defines the grid sizing algorithm , which determines the size of all grid tracks and, by extension, the entire grid.

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

A fixed sizing function (<length> or resolvable <percentage>).

(<length> or resolvable <percentage>). An intrinsic sizing function (min-content, max-content, auto, fit-content()).

(min-content, max-content, auto, fit-content()). A flexible sizing function (<flex>).

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

11.1. Grid Sizing Algorithm

Once the size of each grid area is thus established, the grid items are laid out into their respective containing blocks. The grid area’s width and height are considered definite for this purpose.

Note: Since formulas calculated using only definite sizes, such as the stretch fit formula, are also definite, the size of a grid item which is stretched is also considered definite.

11.2. Track Sizing Terminology

Note: Remember that gutters are treated as fixed-size tracks— tracks with their min and max sizing functions both set to the gutter’s used size— for the purpose of the grid sizing algorithm. Their widths need to be incorporated into the track sizing algorithm’s calculations accordingly.

11.3. Track Sizing Algorithm

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. There are 5 steps:

11.4. Initialize Track Sizes

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

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

In all cases, if the growth limit is less than the base size, increase the growth limit to match the base size.

Note: Gutters are treated as empty fixed-size tracks for the purpose of the track sizing algorithm.

11.5. Resolve Intrinsic Track Sizes

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.

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

Note: Remember that fit-content() and auto max track sizing functions are treated the same as max-content except where explicitly specified otherwise.

Note: There is no single way to satisfy intrinsic sizing 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.

11.5.1. Distributing Extra Space Across Spanned Tracks

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

11.6. Maximize Tracks

If the free space is positive, distribute it equally to the base sizes of 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.

If this would cause the grid to be larger than the grid container’s inner size as limited by its max-width/height, then redo this step, treating the available grid space as equal to the grid container’s inner size when it’s sized to its max-width/height.

11.7. Expand 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 grid’s used flex fraction:

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.

11.7.1. 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 .

11.8. Stretch auto Tracks

This step expands tracks that have an auto max track sizing function by dividing any remaining positive, definite free space equally amongst them. If the free space is indefinite, but the grid container has a definite min-width/height, use that size to calculate the free space for this step instead.

12. Fragmenting Grid Layout

Grid containers can break across pages between rows or columns and inside items. The break-* properties apply to grid containers as normal for the formatting context in which they participate. This section defines how they apply to grid items and the contents of grid items.

The following breaking rules refer to the fragmentation container as the “page”. The same rules apply in any other fragmentation context. (Substitute “page” with the appropriate fragmentation container type as needed.) See the CSS Fragmentation Module [CSS3-BREAK].

The exact layout of a fragmented grid container is not defined in this level of Grid Layout. However, breaks inside a grid container are subject to the following rules:

The break-before and break-after properties on grid items are propagated to their grid row. The break-before property on the first row and the break-after property on the last row are propagated to the grid container.

property on the first row and the property on the last row are propagated to the grid container. A forced break inside a grid item effectively increases the size of its contents; it does not trigger a forced break inside sibling items.

Class A break opportunities occur between rows or columns (whichever is in the appropriate axis), and Class C break opportunities occur between the first/last row (column) and the grid container’s content edges. [CSS3-BREAK]

When a grid container is continued after a break, the space available to its grid items (in the block flow direction of the fragmentation context) is reduced by the space consumed by grid container fragments on previous pages. The space consumed by a grid container fragment is the size of its content box on that page. If as a result of this adjustment the available space becomes negative, it is set to zero.

Aside from the rearrangement of items imposed by the previous point, UAs should attempt to minimize distortion of the grid container with respect to unfragmented flow.

12.1. Sample Fragmentation Algorithm

This section is non-normative.

This is a rough draft of one possible fragmentation algorithm, and still needs to be severely cross-checked with the [CSS-FLEXBOX-1] algorithm for consistency. Feedback is welcome; please reference the rules above instead as implementation guidance.

Layout the grid following the § 11 Grid Sizing by using the fragmentation container’s inline size and assume unlimited block size. During this step all grid-row auto and fr values must be resolved. Layout the grid container using the values resolved in the previous step. If a grid area’s size changes due to fragmentation (do not include items that span rows in this decision), increase the grid row size as necessary for rows that either: have a content min track sizing function.

are in a grid that does not have an explicit height and the grid row is flexible. If the grid height is auto, the height of the grid should be the sum of the final row sizes. If a grid area overflows the grid container due to margins being collapsed during fragmentation, extend the grid container to contain this grid area (this step is necessary in order to avoid circular layout dependencies due to fragmentation).

If the grid’s height is specified, steps three and four may cause the grid rows to overflow the grid.

Acknowledgements

This specification is made possible by input from Erik Anderson, Rachel Andrew, Rossen Atanassov, Oriol Brufau, Manuel Rego Casasnovas, Arron Eicholz, Javier Fernandez, Sylvain Galineau, Markus Mielke, Daniel Holbert, John Jansen, Chris Jones, Kathy Kam, Veljko Miljanic, Charbel Nicolas, Mats Palmgren, François Remy, Sergio Villar Senin, Jen Simmons, Christian Stockwell, Eugene Veselov, and the CSS Working Group members, with special thanks to Rossen Atanassov, Alex Mogilevsky, Phil Cupp, and Peter Salas of Microsoft for creating the initial proposal. Thanks also to Eliot Graff for editorial input.

Changes

This section documents the changes since previous publications.

A Disposition of Comments is available.

Major Changes

Minor Changes

Clarifications

A Disposition of Comments is also available.

Major Changes

Significant Adjustments and Fixes

Clarifications

13. Privacy and Security Considerations

Grid introduces no new privacy leaks, or security considerations beyond "implement it correctly".