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Media Queries Level 4

Editor's Draft 19 June 2012

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dev.w3.org/csswg/mediaqueries4/
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Editors:
Florian Rivoal <>
Previous Editors:
Håkon Wium Lie <>
Tantek Çelik <>
Daniel Glazman <>
Anne van Kesteren <>

Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.

Abstract

Media Queries allow authors to adapt the style applied to a document based on the environment the document is being rendered in. [HTML401] and [CSS21] introduced this mechanism, by allowing detection of the media type. For example, a document may use sans-serif fonts when displayed on a screen and serif fonts when printed. ‘screen’ and ‘print’ are two media types that have been defined. Media Queries Level 3 [MEDIAQ] refined this mechanism by allowing detection of individual characteristics, or media features. For example, a document may use a different style when displayed in ‘portrait’ and in ‘landscape’ mode, as detected by the ‘orientation’ media feature.

Media Queries Level 4 describes the mechanism, media types and media features that already existed in [MEDIAQ], and further introduces new media features.

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 “mediaqueries4” in the subject, preferably like this: “[mediaqueries4] …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.

Table of contents

1. Introduction

This section is not normative.

HTML4 [HTML401] and CSS2 [CSS21] currently support media-dependent style sheets tailored for different media types. For example, a document may use different style sheets for screen and print. In HTML4, this can be written as: 

<link rel="stylesheet" type="text/css" media="screen" class="sans-serif.css">
<link rel="stylesheet" type="text/css" media="print" class="serif.css">

Inside a CSS style sheet, one can declare that sections apply to certain media types: 

@media screen {
  * { font-family: sans-serif }
}

The ‘print’ and ‘screen’ media types are defined in HTML4. The complete list of media types in HTML4 is: ‘aural’, ‘braille’, ‘handheld’, ‘print’, ‘projection’, ‘screen’, ‘tty’, ‘tv’. CSS2 defines the same list, deprecates ‘aural’ and adds ‘embossed’ and ‘speech’. Also, ‘all’ is used to indicate that the style sheet applies to all media types.

Media-specific style sheets are supported by several user agents. The most commonly used feature is to distinguish between ‘screen’ and ‘print’.

There have been requests for ways to describe in more detail what type of output devices a style sheet applies to. Fortunately HTML4 foresaw these requests and defined a forward-compatible syntax for media types. Here is a quote from HTML4, section 6.13:

Future versions of HTML may introduce new values and may allow parameterized values. To facilitate the introduction of these extensions, conforming user agents must be able to parse the media attribute value as follows:

  1. The value is a comma-separated list of entries. For example, 
    media="screen, 3d-glasses, print and resolution > 90dpi"

    is mapped to:

    "screen"
"3d-glasses"
"print and resolution > 90dpi"
  2. Each entry is truncated just before the first character that isn't a US ASCII letter [a-zA-Z] (Unicode decimal 65-90, 97-122), digit [0-9] (Unicode hex 30-39), or hyphen (45). In the example, this gives: 
    "screen"
"3d-glasses"
"print"

Media queries, as described in this specification, build on the mechanism outlined in HTML4. The syntax of media queries fit into the media type syntax reserved in HTML4. The media attribute of HTML4 also exists in XHTML and generic XML. The same syntax can also be used inside in the ‘@media’ and ‘@import’ rules of CSS.

However, the parsing rules for media queries are incompatible with those of HTML4 so that they are consistent with those of media queries used in CSS.

HTML5 [HTML5] (at the moment of writing still work in progress) references the Media Queries specification directly and thus updates the rules for HTML.

1.1. Module interactions

This module replaces and extends the Media Queries, Media Type and Media Features defined in [CSS21] sections 7 and in [MEDIAQ].

1.2. Values

This section is normative

Value types not defined in this specification, such as <integer>, <number> or <resolution>, are defined in [CSS3VAL]. Other CSS modules may expand the definitions of these value types.

This specification also introduces one new value type.

The <ratio> value type is a positive (not zero or negative) <integer> followed by optional whitespace, followed by a solidus (‘/’), followed by optional whitespace, followed by a positive <integer>.

1.3. Units

This section is normative

The units used in media queries are the same as in other parts of CSS, as defined in [CSS3VAL]. For example, the pixel unit represents CSS pixels and not physical pixels.

Relative units in media queries are based on the initial value, which means that units are never based on results of declarations. For example, in HTML, the ‘em’ unit is relative to the initial value of ‘font-size’.

2. Media Queries

A media query consists of an optional media type and zero or more expressions that check for the conditions of particular media features.

Statements regarding media queries in this section assume the syntax section is followed. Media queries that do not conform to the syntax are discussed in the error handling section. I.e. the syntax takes precedence over requirements in this section.

Here is a simple example written in HTML:

<link rel="stylesheet" media="screen and (color)" class="example.css" />

This example expresses that a certain style sheet (example.css) applies to devices of a certain media type (‘screen’) with certain feature (it must be a color screen).

Here the same media query written in an @import-rule in CSS:

@import url(color.css) screen and (color);

A media query is a logical expression that is either true or false. A media query is true if the media type of the media query matches the media type of the device where the user agent is running (as defined in the "Applies to" line), and all expressions in the media query are true.

A shorthand syntax is offered for media queries that apply to all media types; the keyword ‘all’ can be left out (along with the trailing ‘and’). I.e. if the media type is not explicitly given it is ‘all’.

I.e. these are identical:

@media all and (min-px) { … }
@media (min-px) { … }

As are these:

@media (orientation: portrait) { … }
@media all and (orientation: portrait) { … }

Several media queries can be combined in a media query list. A comma-separated list of media queries. If one or more of the media queries in the comma-separated list are true, the whole list is true, and otherwise false. In the media queries syntax, the comma expresses a logical OR, while the ‘and’ keyword expresses a logical AND.

Here is an example of several media queries in a comma-separated list using the an @media-rule in CSS:

@media screen and (color), projection and (color) { … }

If the media query list is empty (i.e. the declaration is the empty string or consists solely of whitespace) it evaluates to true.

I.e. these are equivalent:

@media all { … }
@media { … }

The logical NOT can be expressed through the ‘not’ keyword. The presence of the keyword ‘not’ at the beginning of the media query negates the result. I.e., if the media query had been true without the ‘not’ keyword it will become false, and vice versa. User agents that only support media types (as described in HTML4) will not recognize the ‘not’ keyword and the associated style sheet is therefore not applied. 

<link rel="stylesheet" media="not screen and (color)" class="example.css" />

The keyword ‘only’ can also be used to hide style sheets from older user agents. User agents must process media queries starting with ‘only’ as if the ‘only’ keyword was not present. 

<link rel="stylesheet" media="only screen and (color)" class="example.css" />

The media queries syntax can be used with HTML, XHTML, XML [XMLSTYLE] and the @import and @media rules of CSS.

Here is the same example written in HTML, XHTML, XML, @import and @media:

<link rel="stylesheet" media="screen and (color), projection and (color)" rel="stylesheet" class="example.css">
<link rel="stylesheet" media="screen and (color), projection and (color)" rel="stylesheet" class="example.css" />
<?xml-stylesheet media="screen and (color), projection and (color)" rel="stylesheet" class="example.css" ?>
@import url(example.css) screen and (color), projection and (color);
@media screen and (color), projection and (color) { … }

The [XMLSTYLE] specification has not yet been updated to use media queries in the media pseudo-attribute.

If a media feature does not apply to the device where the UA is running, expressions involving the media feature will be false.

The media feature ‘device-aspect-ratio’ only applies to visual devices. On an aural device, expressions involving ‘device-aspect-ratio’ will therefore always be false:

<link rel="stylesheet" media="aural and (device-aspect-ratio: 16/9)" class="example.css" />

Expressions will always be false if the unit of measurement does not apply to the device.

The ‘px’ unit does not apply to ‘speech’ devices so the following media query is always false:

<link rel="stylesheet" media="speech and (min-device-px)" class="example.css" />

Note that the media queries in this example would have been true if the keyword ‘not’ had been added to the beginning of the media query.

To avoid circular dependencies, it is never necessary to apply the style sheet in order to evaluate expressions. For example, the aspect ratio of a printed document may be influenced by a style sheet, but expressions involving ‘device-aspect-ratio’ will be based on the default aspect ratio of the user agent.

User agents are expected, but not required, to re-evaluate and re-layout the page in response to changes in the user environment, for example if the device is tilted from landscape to portrait mode.

3. Syntax

The media query syntax is described in terms of the CSS2 grammar. As such, rules not defined here are defined in CSS2. The media_query_list production defined below replaces the media_list production from CSS2. [CSS21] 

media_query_list
 : S* [media_query [ ',' S* media_query ]* ]?
 ;
media_query
 : [ONLY | NOT]? S* media_type S* [ AND S* expression ]*
 | expression [ AND S* expression ]*
 ;
media_type
 : IDENT
 ;
expression
 : '(' S* media_feature S* [ ':' S* expr ]? ')' S*
 ;
media_feature
 : IDENT
 ;

COMMENT tokens, as defined by CSS2, do not occur in the grammar (to keep it readable), but any number of these tokens may appear anywhere between other tokens. [CSS21]

The following new definitions are introduced: 

L  l|\\0{0,4}(4c|6c)(\r\n|[ \t\r\n\f])?|\\l
Y  y|\\0{0,4}(59|79)(\r\n|[ \t\r\n\f])?|\\y

The following new tokens are introduced: 

{O}{N}{L}{Y}      {return ONLY;}
{N}{O}{T}         {return NOT;}
{A}{N}{D}         {return AND;}
{num}{D}{P}{I}    {return RESOLUTION;}
{num}{D}{P}{C}{M} {return RESOLUTION;}

RESOLUTION is to be added to the CSS2 term production.

CSS style sheets are generally case-insensitive, and this is also the case for media queries.

In addition to conforming to the syntax, each media query needs to use media types and media features according to their respective specification in order to be considered conforming.

Only the first media query is conforming in the example below because the "example" media type does not exist.

@media all { body { background:lime } }
@media example { body { background:red } }

3.1. Error Handling

For media queries that are not conforming user agents need to follow the rules described in this section.

4. Media features

Syntactically, media features resemble CSS properties: they have names and accept certain values. There are, however, several important differences between properties and media features:

For example, the ‘color’ media feature can form expressions without a value (‘(color)’), or with a value (‘(min-color: 1)’).

This specification defines media features usable with visual and tactile devices. Similarly, media features can be defined for aural media types.

4.1. width

Value: <length>
Applies to: visual and tactile media types
Accepts min/max prefixes: yes

The ‘width’ media feature describes the width of the targeted display area of the output device. For continuous media, this is the width of the viewport (as described by CSS2, section 9.1.1 [CSS21]) including the size of a rendered scroll bar (if any). For paged media, this is the width of the page box (as described by CSS2, section 13.2 [CSS21]).

A specified <length> cannot be negative.

For example, this media query expresses that the style sheet is usable on printed output wider than 25cm:

<link rel="stylesheet" media="print and (min-cm)" class="…" />

This media query expresses that the style sheet is usable on devices with viewport (the part of the screen/paper where the document is rendered) widths between 400 and 700 pixels:

@media screen and (min-px) and (max-px) { … }

This media query expresses that style sheet is usable on screen and handheld devices if the width of the viewport is greater than 20em.

@media handheld and (min-em), 
  screen and (min-em) { … }

The ‘em’ value is relative to the initial value of ‘font-size’.

4.2. height

Value: <length>
Applies to: visual and tactile media types
Accepts min/max prefixes: yes

The ‘height’ media feature describes the height of the targeted display area of the output device. For continuous media, this is the height of the viewport including the size of a rendered scroll bar (if any). For paged media, this is the height of the page box.

A specified <length> cannot be negative.

4.3. device-width

Value: <length>
Applies to: visual and tactile media types
Accepts min/max prefixes: yes

The ‘device-width’ media feature describes the width of the rendering surface of the output device. For continuous media, this is the width of the screen. For paged media, this is the width of the page sheet size.

A specified <length> cannot be negative. 

@media screen and (device-px) { … }

In the example above, the style sheet will apply only to screens that currently displays exactly 800 horizontal pixels. The ‘px’ unit is of the logical kind, as described in the Units section.

4.4. device-height

Value: <length>
Applies to: visual and tactile media types
Accepts min/max prefixes: yes

The ‘device-height’ media feature describes the height of the rendering surface of the output device. For continuous media, this is the height of the screen. For paged media, this is the height of the page sheet size.

A specified <length> cannot be negative. 

<link rel="stylesheet" media="screen and (device-px)" />

In the example above, the style sheet will apply only to screens that have exactly 600 vertical pixels. Note that the definition of the ‘px’ unit is the same as in other parts of CSS.

4.5. orientation

Value: portrait | landscape
Applies to: bitmap media types
Accepts min/max prefixes: no

The ‘orientation’ media feature is ‘portrait’ when the value of the ‘height’ media feature is greater than or equal to the value of the ‘width’ media feature. Otherwise ‘orientation’ is ‘landscape’. 

@media all and (orientation:portrait) { … }
@media all and (orientation:landscape) { … }

4.6. aspect-ratio

Value: <ratio>
Applies to: bitmap media types
Accepts min/max prefixes: yes

The ‘aspect-ratio’ media feature is defined as the ratio of the value of the ‘width’ media feature to the value of the ‘height’ media feature.

4.7. device-aspect-ratio

Value: <ratio>
Applies to: bitmap media types
Accepts min/max prefixes: yes

The ‘device-aspect-ratio’ media feature is defined as the ratio of the value of the ‘device-width’ media feature to the value of the ‘device-height’ media feature.

For example, if a screen device with square pixels has 1280 horizontal pixels and 720 vertical pixels (commonly referred to as "16:9"), the following Media Queries will all match the device:

@media screen and (device-aspect-ratio: 16/9) { … }
@media screen and (device-aspect-ratio: 32/18) { … }
@media screen and (device-aspect-ratio: 1280/720) { … }
@media screen and (device-aspect-ratio: 2560/1440) { … }

4.8. color

Value: <integer>
Applies to: visual media types
Accept min/max prefixes: yes

The ‘color’ media feature describes the number of bits per color component of the output device. If the device is not a color device, the value is zero.

A specified <integer> cannot be negative.

For example, these two media queries express that a style sheet applies to all color devices:

@media all and (color) { … }
@media all and (min-color: 1) { … }

This media query expresses that a style sheet applies to color devices with 2 or more bits per color component:

@media all and (min-color: 2) { … }

If different color components are represented by different number of bits, the smallest number is used.

For instance, if an 8-bit color system represents the red component with 3 bits, the green component with 3 bits and the blue component with 2 bits, the ‘color’ media feature will have a value of 2.

In a device with indexed colors, the minimum number of bits per color component in the lookup table is used.

The described functionality is only able to describe color capabilities at a superficial level. If further functionality is required, RFC2531 [RFC2531] provides more specific media features which may be supported at a later stage.

4.9. color-index

Value: <integer>
Applies to: visual media types
Accepts min/max prefixes: yes

The ‘color-index’ media feature describes the number of entries in the color lookup table of the output device. If the device does not use a color lookup table, the value is zero.

A specified <integer> cannot be negative.

For example, here are two ways to express that a style sheet applies to all color index devices:

@media all and (color-index) { … }
@media all and (min-color-index: 1) { … }

This media query expresses that a style sheet applies to a color index device with 256 or more entries:

<?xml-stylesheet media="all and (min-color-index: 256)" 
  class="www.example.com/…" ?>

4.10. monochrome

Value: <integer>
Applies to: visual media types
Accepts min/max prefixes: yes

The ‘monochrome’ media feature describes the number of bits per pixel in a monochrome frame buffer. If the device is not a monochrome device, the output device value will be 0.

A specified <integer> cannot be negative.

For example, here are two ways to express that a style sheet applies to all monochrome devices:

@media all and (monochrome) { … }
@media all and (min-monochrome: 1) { … }

Express that a style sheet applies to monochrome devices with more than 2 bits per pixels:

@media all and (min-monochrome: 2) { … }

Express that there is one style sheet for color pages and another for monochrome:

<link rel="stylesheet" media="print and (color)" class="…" />
<link rel="stylesheet" media="print and (monochrome)" class="…" />

4.11. resolution

Value: <resolution>
Applies to: bitmap media types
Accepts min/max prefixes: yes

The ‘resolution’ media feature describes the resolution of the output device, i.e. the density of the pixels. When querying devices with non-square pixels, in ‘min-resolution’ queries the least-dense dimension must be compared to the specified value and in ‘max-resolution’ queries the most-dense dimensions must be compared instead. A ‘resolution’ (without a "min-" or "max-" prefix) query never matches a device with non-square pixels.

For printers, this corresponds to the screening resolution (the resolution for printing dots of arbitrary color).

For example, this media query expresses that a style sheet is usable on devices with resolution greater than 300 dots per CSS ‘inch’:

@media print and (min-resolution: 300dpi) { … }

This media query expresses that a style sheet is usable on devices with resolution greater than 118 dots per CSS ‘centimeter’:

@media print and (min-resolution: 118dpcm) { … }

4.12. scan

Value: progressive | interlace
Applies to: "tv" media types
Accepts min/max prefixes: no

The ‘scan’ media feature describes the scanning process of "tv" output devices.

For example, this media query expresses that a style sheet is usable on tv devices with progressive scanning:

@media tv and (scan: progressive) { … }

4.13. grid

Value: <integer>
Applies to: visual and tactile media types
Accepts min/max prefixes: no

The ‘grid’ media feature is used to query whether the output device is grid or bitmap. If the output device is grid-based (e.g., a "tty" terminal, or a phone display with only one fixed font), the value will be 1. Otherwise, the value will be 0.

Only 0 and 1 are valid values. (This includes -0.) Thus everything else creates a malformed media query.

Here are two examples:

@media handheld and (grid) and (max-em) { … }
@media handheld and (grid) and (device-max-em) { … }

4.14. script

Value: <integer>
Applies to:all media types
Accepts min/maxprefixes: no

The ‘script’ media feature is used to query whether ECMAscript is supported on the current document. If the user agent supports ECMAscript, and that support is active for the current document the value must be 1. Otherwise, the value must be 0.

Some user agents have the ability to turn off ECMAscript support on a per script basis or per domain basis, allowing some, but not all, scripts to run in a particular document. The ‘script’ media feature does not allow fine grained detection of which script is allowed to run. In this scenario, the value of the ‘script’ media feature should be 1 if scripts originating on the same domain as the document are allowed to run, and 0 otherwise.

A future level of CSS may extend this media feature to allow fine-grained detection of which script is allowed to run.

Only 0 and 1 are valid values. (This includes -0.) Thus everything else creates a malformed media query.

4.15. pointer

Value: none | coarse | fine
Applies to: visual and tactile media types
Accepts min/max prefixes: no

The ‘pointer’ media feature is used to query about the presence and accuracy of a pointing device such as a mouse. If a device has multiple input mechanisms, it is recommended that the UA reports the characteristics of the least capable pointing device of the primary input mechanisms. This media query takes the following values:

‘none’
The input mechanism of the device does not include a pointing device.
‘coarse’
The input mechanism of the device includes a pointing device of limited accuracy.
‘fine’
The input mechanism of the device includes an accurate pointing device.

Both ‘coarse’ and ‘fine’ indicate the presence of a pointing device, but differ in accuracy. A pointing device with which it would be difficult or impossible to reliably pick one of several small adjacent targets would qualify as ‘coarse’.

Typical examples of a ‘fine’ pointing system are a mouse, a track-pad or a stylus-based touch screen. Finger-based touch screens would qualify as ‘coarse’.

For accessibility reasons, even on devices whose pointing device can be described as ‘fine’, the UA may give a value of ‘coarse’ or ‘none’ to this media query, to indicate that the user has difficulties manipulating the input device accurately or at all. 

/* Make radio buttons and check boxes larger if we have an inaccurate pointing device */
@media (pointer:coarse) {
	input[type="checkbox"], input[type="radio"] {
		min-px;
		min-px;
		background:transparent;
	}
}

4.16. hover

Value: <integer>
Applies to: visual and tactile media types
Accepts min/max prefixes: no

The ‘hover’ media feature is used to query whether primary pointing system used on the output device can hover or not. If it can, the value will be 1. Otherwise, the value wil

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