1. Introduction
This section is not normative.
HTML4 [HTML401] defined a mechanism to support media-dependent style sheets, tailored for different media types. For example, a document may use different style sheets for screen and for print. In HTML, this can be written as:
<link rel="stylesheet" type="text/css" media="screen" href="style.css"> <link rel="stylesheet" type="text/css" media="print" href="print.css">
CSS adapted and extended this functionality with its @media and @import rules, adding the ability to query the value of individual features:
@media screen { * { font-family: sans-serif } }
Similarly, stylesheets can be conditionally imported based on media queries:
@import "print-styles.css" print;
Media queries can be used with HTML, XHTML, XML [XMLSTYLE] and the @import and @media rules of CSS.
<link media="screen and (color), projection and (color)" rel="stylesheet" href="example.css"> <link media="screen and (color), projection and (color)" rel="stylesheet" href="example.css" /> <?xml-stylesheet media="screen and (color), projection and (color)" rel="stylesheet" href="example.css" ?> @import url(example.css) screen and (color), projection and (color); @media screen and (color), projection and (color) { … }
Note: The [XMLSTYLE] specification has not yet been updated to
use media queries in the media
pseudo-attribute.
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
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.
1.3. Units
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 length 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, defined by the user agent or the user’s preferences, not any styling on the page.
2. Media Queries
A media query is a method of testing certain aspects of the user agent or device that the document is being displayed in. Media queries are (almost) always independent of the contents of the document, its styling, or any other internal aspect; they’re only dependent on “external” information unless another feature explicitly specifies that it affects the resolution of Media Queries, such as the @viewport rule.
The syntax of a media query consists of an optional media query modifier, an optional media type, and zero or more media features:
A media query is a logical expression that is either true or false. A media query is true if:
-
the media type, if specified, matches the media type of the device where the user agent is running, and
-
the media condition is true.
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 §3.2 Error Handling. I.e. the syntax takes precedence over requirements in this section.
<link rel="stylesheet" media="screen and (color)" href="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 is the same media query written in an @import-rule in CSS:
@import url(example.css) screen and (color);
User agents must re-evaluate media queries in response to changes in the user environment that they’re aware of, for example if the device is tiled from landscape to portrait orientation, and change the behavior of any constructs dependent on those media queries accordingly.
Unless another feature explicitly specifies that it affects the resolution of Media Queries, it is never necessary to apply a style sheet in order to evaluate expressions.
Note: CSS Device Adaptation [CSS-DEVICE-ADAPT]] defines how @viewport rules interact with Media Queries.
2.1. Combining Media Queries
Several media queries can be combined into a comma-separated media query list.
A media query list is true if any of its component media queries are true, and false only if all of its component media queries are false.
@media screen and (color), projection and (color) { … }
An empty media query list evaluates to true.
2.2. Media Query Modifiers
A media query may optionally be prefixed by a single media query modifier, which is a single keyword which alters the meaning of the following media query.
2.2.1. Negating a Media Query: the not keyword
An individual media query can have its result negated by prefixing it with the keyword not. If the media query would normally evaluate to true, prefixing it with not makes it evaluate to false, and vice versa.
<link rel="stylesheet" media="not screen and (color)" href="example.css" />
2.2.2. Hiding a Media Query From Legacy User Agents: the only keyword
The concept of media queries originates from HTML4 [HTML401]. That specification only defined media types, but had a forward-compatible syntax that accommodated the addition of future concepts like media features: it would consume the characters of a media query up to the first non-alphanumeric character, and interpret that as a media type, ignoring the rest. For example, the media query screen and (color) would be truncated to just screen.
Unfortunately, this means that legacy user agents using this error-handling behavior will ignore any media features in a media query, even if they’re far more important than the media type in the query. This can result in styles accidentally being applied in inappropriate situations.
To hide these media queries from legacy user agents, the media query can be prefixed with the keyword only. The only keyword has no effect on the media query’s result, but will cause the media query to be parsed by legacy user agents as specifying the unknown media type “only”, and thus be ignored.
<link>
element
will not be used by legacy user agents,
even if they would normally match the screen media type.
<link rel="stylesheet" media="only screen and (color)" href="example.css" />
Note: Note that the only keyword can only be used before a media type. A media query consisting only of media features, or one with another media query modifier like not, will be treated as false by legacy user agents automatically.
Note: At the time of publishing this specification, such legacy user agents are extremely rare, and so using the only modifier is rarely, if ever, necessary.
2.3. Media Types
A media type is a broad category of user-agent devices
on which a document may be displayed.
The original set of media types were defined in HTML4,
for the media
attribute on <link>
elements.
Unfortunately, media types have proven insufficient as a way of discriminating between devices with different styling needs. Some categories which were originally quite distinct, such as screen and handheld, have blended significantly in the years since their invention. Others, such as tty or tv, expose useful differences from the norm of a full-featured computer monitor, and so are potentially useful to target with different styling, but the definition of media types as mutually exclusive makes it difficult to use them in a reasonable manner; instead, their exclusive aspects are better expressed as media features such as grid or scan.
As such, the following media types are defined for use in media queries:
- all
- Matches all devices.
- Matches printers, and devices intended to reproduce a printed display, such as a web browser showing a document in “Print Preview”.
- screen
- Matches all devices that aren’t matched by print or speech.
- speech
- Matches screenreaders and similar devices that “read out” a page.
In addition, the following deprecated media types are defined. Authors must not use these media types; instead, it is recommended that they select appropriate media features that better represent the aspect of the device that they are attempting to style against.
User agents must recognize the following media types as valid, but must make them match nothing.
Note: It is expected that all of the media types will also be deprecated in time, as appropriate media features are defined which capture their important differences.
2.4. Media Features
A media feature is a more fine-grained test than media types, testing a single, specific feature of the user agent or display device.
Syntactically, media features resemble CSS properties: they consist of a feature name, a colon, and a value to test for. They may also be written in boolean form as just a feature name, or in range form with a comparison operator.
There are, however, several important differences between properties and media features:
- Properties are used to give information about how to present a document. Media features are used to describe requirements of the output device.
- Media features are always wrapped in parentheses and combined with the and keyword, like (color) and (min-width: 600px), rather than being separated with semicolons.
- A media feature may be given with only its name (omitting the colon and value) to evaluate the feature in a boolean context. This is a convenient shorthand for features that have a reasonable value representing 0 or “none”. For example, (color) is true is the color media feature is non-zero.
- Media features with “range” type can be written in a range context, which uses standard mathematical comparison operators rather than a colon, or have their feature names prefixed with “min-” or “max-”.
- Properties sometimes accept complex values, e.g., calculations that involve several other values. Media features only accept single values: one keyword, one number, etc.
If a media feature references a concept which does not exist on the device where the UA is running (for example, speech UAs do not have a concept of “width”), the media feature must always evaluate to false.
<link media="speech and (device-aspect-ratio: 16/9)" rel="stylesheet" href="example.css">
2.4.1. Media Feature Types: “range” and “discrete”
Every media feature defines its “type” as either “range” or “discrete” in its definition table.
“Discrete” media features,
like pointer or scripting,
take their values from a set.
The values may be keywords
or boolean numbers (0 and 1),
but the common factor is that there’s no intrinsic “order” to them—
“Range” media features like width, on the other hand, take their values from a range. Any two values can be compared to see which is lesser and which is greater.
The only significant difference between the two types is that “range” media features can be evaluated in a range context and accept “min-” and “max-” prefixes on their name.
Doing either of these changes the meaning of the feature—
On the other hand, (width: 600px) by itself is only true when the viewport’s width is exactly 600px. If it’s less or greater than 600px, it’ll be false.
2.4.2. Evaluating Media Features in a Boolean Context
While media features normally have a syntax similar to CSS properties, they can also be written more simply as just the feature name, like (color).
When written like this, the media feature is evaluated in a boolean context. If the feature would be true for any value other than the number 0, a <dimension> with the value 0, or the keyword none, the media feature evaluates to true. Otherwise, it evaluates to false.
For example, scripting is typically written as (scripting) to test if scripting is enabled, or not (scripting) to see if it’s disabled.
It can still be given an explicit value as well, with (scripting: enabled) equal to (scripting), and (scripting: none) equal to not (scripting).
For example, (pointer) is useful, as pointer has a none value to indicate there’s no pointing device at all on the device. On the other hand, (scan) is just always true or always false (depending on whether it applies at all to the device), as there’s no value that means “false”.
2.4.3. Evaluating Media Features in a Range Context
Media features with a “range” type can be alternately written in a range context that takes advantage of the fact that their values are ordered, using ordinary mathematical comparison operators:
Note: This syntax is new to Level 4 of Mediaqueries, and thus is not as widely supported at the moment as the min-/max- prefixes.
The basic form, consisting of a feature name, a comparison operator, and a value, returns true if the relationship is true.
The remaining forms, with the feature name nested between two value comparisons, returns true if both comparisons are true.
2.4.4. Using “min-” and “max-” Prefixes On Range Features
Rather than evaluating a “range” type media feature in a range context, as described above, the feature may be written as a normal media feature, but with a “min-” or “max-” prefix on the feature name.
This is equivalent to evaluating the feature in a range context, as follows:
- Using a “min-” prefix on a feature name is equivalent to using the “>=” operator. For example, (min-height: 600px) is equivalent to ''(height >= 600px)''.
- Using a “max-” prefix on a feature name is equivalent to using the “<=” operator. For example, (max-width: 40em) is equivalent to ''(width <= 40em)''.
“Discrete” type properties do not accept “min-” or “max-” prefixes. Adding such a prefix to a “discrete” type media feature simply results in an unknown feature name.
Attempting to evaluate a min/max prefixed media feature in a boolean context is invalid and a syntax error.
2.5. Combining Media Features
Multiple media features can be combined together into a media condition using full boolean algebra (not, and, or).
-
Any media feature can be negated by placing not before it. For example, not (color) inverts the meaning of (color)—
since (color) matches a device with any kind of color display, not (color) matches a device without any kind of color display. -
Two or more media features can be chained together, such that the query is only true if all of the media features are true, by placing and between them. For example, (width < 600px) and (height < 600px) only matches devices whose screens are smaller than 600px wide in both dimensions.
-
Alternately, two or more media features can be chained together, such that the query is true if any of the media features are true, by plaing or between them. For example, (update: slow) or (hover: none) matches if the device is slow to update the screen (such as an e-reader) or the device has no hover capability, perhaps indicating that one should use a layout that displays more information rather than compactly hiding it until the user hovers.
-
Media conditions can be grouped by wrapping them in parentheses () which can then be nested within a condition the same as a single media query. For example, (not (color)) or (hover) is true on devices that are monochrome and/or that have hover capabilities. If one instead wanted to query for a device that was monochrome and didn’t have hover capabilities, it must instead be written as not ((color) or (hover)) (or, equivalently, as (not (color)) and (not (hover))).
It is invalid to mix and and or and not at the same “level” of a media query. For example, (color) and (pointer) or (hover) is illegal, as it’s unclear what was meant. Instead, parentheses can be used to group things using a particular joining keyword, yielding either (color) and ((pointer) or (hover)) or ((color) and (pointer)) or (hover). These two have very different meanings: if only (hover) is true, the first one evaluates to false but the second evaluates to true.
3. Syntax
Informal descriptions of the media query syntax appear in the prose and railroad diagrams in previous sections. The formal media query syntax is described in this section, with the rule/property grammar syntax defined in [CSS3SYN] and [CSS3VAL].
To parse a <media-query-list> production, parse a comma-separated list of component values, then parse each entry in the returned list as a <media-query>. Its value is the list of <media-query>s so produced.
Note: This explicit definition of <media-query-list> parsing is necessary to make the error-recovery behavior of media query lists well-defined.
Note: This definition of <media-query-list> parsing intentionally accepts an empty list.
<media-query> = <media-condition> | [ not | only ]? <media-type> [ and <media-condition-without-or> ]? <media-type> = <ident> <media-condition> = <media-not> | <media-and> | <media-or> | <media-in-parens> <media-condition-without-or> = <media-not> | <media-and> | <media-in-parens> <media-not> = not <media-in-parens> <media-and> = <media-in-parens> [ and <media-in-parens> ]+ <media-or> = <media-in-parens> [ or <media-in-parens> ]+ <media-in-parens> = ( <media-condition> ) | <media-feature> | <general-enclosed> <media-feature> = ( [ <mf-plain> | <mf-boolean> | <mf-range> ] ) <mf-plain> = <mf-name> : <mf-value> <mf-boolean> = <mf-name> <mf-range> = <mf-name> [ '<' | '>' ]? '='? <mf-value> | <mf-value> [ '<' | '>' ]? '='? <mf-name> | <mf-value> '<' '='? <mf-name> '<' '='? <mf-value> | <mf-value> '>' '='? <mf-name> '>' '='? <mf-value> <mf-name> = <ident> <mf-value> = <number> | <dimension> | <ident> | <ratio> <general-enclosed> = [ <function-token> <any-value> ) ] | ( <ident> <any-value> )
The <media-type> production does not include the keywords only, not, and, and or.
No whitespace is allowed between the “<” or “>” <delim-token>s and the following “=” <delim-token>, if it’s present.
Note: Whitespace is required between a not, and, or or keyword and the following ( character, because without it that would instead parse as a <function-token>. This is not made explicitly invalid because it’s already covered by the above grammar. It’s fine to have whitespace between a ) and a following keyword, however.
When parsing the <media-in-parens> production, the <general-enclosed> branch must only be chosen if the input does not match either of the preceding branches. <general-enclosed> exists to allow for future expansion of the grammar in a reasonably compatible way.
3.1. Evaluating Media Queries
Each of the major terms of <media-condition> or <media-condition-without-or> is associated with a boolean result, as follows:
- <media-condition>
- <media-condition-without-or>
- <media-in-parens>
- <media-condition-without-or>
- The result is the result of the child term.
- <media-not>
- The result is the negation of the <media-in-parens> term. The negation of unknown is unknown.
- <media-and>
- The result is true if all of the <media-in-parens> child terms are true, false if at least one of the <media-in-parens> child terms are false, and unknown otherwise.
- <media-or>
- The result is false if all of the <media-in-parens> child terms are false, true if at least one of the <media-in-parens> child terms are true, and unknown otherwise.
- <general-enclosed>
-
The result is unknown.
Authors must not use <general-enclosed> in their stylesheets. It exists only for future-compatibility, so that new syntax additions do not invalidate too much of a <media-condition> in older user agents.
- <media-feature>
- The result is the result of evaluating the specified media feature.
If the result of any of the above productions is used in any context that expects a two-valued boolean, “unknown” must be converted to “false”.
Note: This means that, for example, when a media query is used in a @media rule, if it resolves to “unknown” it’s treated as “false” and fails to match.
In general, an unknown value showing up in a formula will cause the formula to be unknown as well, as substituting “true” for the unknown will give the formula a different result than substituting “false”. The only way to eliminate an unknown value is to use it in a formula that will give the same result whether the unknown is replaced with a true or false value. This occurs when you have “false AND unknown” (evaluates to false regardless) and “true OR unknown” (evaluates to true regardless).
This logic was adopted because <general-enclosed> needs to be assigned a truth value. In standard boolean logic, the only reasonable value is “false”, but this means that not unknown(function) is true, which can be confusing and unwanted. Kleen’s 3-valued logic ensures that unknown things will prevent a media query from matching, unless their value is irrelevant to the final result.
3.2. Error Handling
A media query that does not match the grammar in the previous section must be replaced by not all during parsing.
Note: Note that a grammar mismatch does not wipe out an entire media query list, just the problematic media query. The parsing behavior defined above automatically recovers at the next top-level comma.
@media (example, all,), speech { /* only applicable to speech devices */ } @media &test, speech { /* only applicable to speech devices */ }
Both of the above media query lists are turned into not all, speech during parsing, which has the same truth value as just speech.
Note that error-recovery only happens at the top-level of a media query; anything inside of an invalid parenthesized block will just get turned into not all as a group. For example:
@media (example, speech { /* rules for speech devices */ }
Because the parenthesized block is unclosed, it will contain the entire rest of the stylesheet from that point (unless it happens to encounter an unmatched “)” character somewhere in the stylesheet), and turn the entire thing into a not all media query.
An unknown <media-type> must be treated as not matching.
But not unknown is true, as the not negates the false media type.
An unknown <mf-name> or <mf-value>, or disallowed <mf-value>, results in the value “unknown”. A <media-query> whose value is “unknown” must be replaced with not all.
<link media="screen and (max-weight: 3kg) and (color), (color)"rel="stylesheet" href="example.css" />
As max-weight is an unknown media feature, this media query list is turned into not all, (color), which is equivalent to just (color).
@media (min-orientation:portrait) { … }
The orientation feature does not accept prefixes, so this is considered an unknown media feature, and turned into not all.
@media (min-width: -100px) { … }
@media test;,all { body { background:lime } }
The media query test;,all is, parsed by itself, equivalent to not all, all, which is always true. However, CSS’s parsing rules cause the @media rule, and thus the media query, to end at the semicolon. The remainder of the text is treated as a style rule with an invalid selector and contents.
4. Screen/Device Dimensions Media Features
4.1. Screen Width: the width feature
Name: | width |
---|---|
For: | @media |
Value: | <length> |
Type: | range |
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]).
<length>s are interpreted according to §1.3 Units.
Negative <length>s are invalid.
<link rel="stylesheet" media="print and (min-width: 25cm)" href="http://…" />
@media (400px <= min-width <= 700px) { … }
@media (min-width: 20em) { … }
The em value is relative to the initial value of font-size.
4.2. Screen Height: the height feature
Name: | height |
---|---|
For: | @media |
Value: | <length> |
Type: | range |
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.
<length>s are interpreted according to §1.3 Units.
Negative <length>s are invalid.
4.3. Screen Aspect-Ratio: the aspect-ratio feature
Name: | aspect-ratio |
---|---|
For: | @media |
Value: | <ratio> |
Type: | range |
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.
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>. <ratio>s can be ordered or compared by transforming them into the number obtained by dividing their first <integer> by their second <integer>.
4.4. Screen Orientation: the orientation feature
Name: | orientation |
---|---|
For: | @media |
Value: | portrait | landscape |
Type: | discrete |
- portrait
- 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.
- landscape
- Otherwise orientation is landscape.
@media (orientation:portrait) { … }
5. Display Quality Media Features
5.1. Screen Resolution: the resolution feature
Name: | resolution |
---|---|
For: | @media |
Value: | <resolution> | infinite |
Type: | range |
The resolution media feature describes the resolution of the output device, i.e. the density of the pixels, taking into account the page zoom but assuming a pinch zoom of 1.0.
When querying media with non-square pixels, resolution queries the density in the vertical dimension.
For printers, this corresponds to the screening resolution (the resolution for printing dots of arbitrary color). Printers might have a different resolution for grayscale printing.
For output mediums that have no physical constraints on resolution (such as outputting to vector graphics), this feature must match the infinite value. For the purpose of evaluating this media feature in the range context, infinite must be treated as larger than any possible <resolution>. (That is, a query like (resolution > 1000dpi) will be true for an infinite media.)
@media (resolution >= 2dppx)
@media print and (min-resolution: 300dpi) { … }
This media query is equivalent, but uses the CSS cm unit:
@media print and (min-resolution: 118dpcm) { … }
If the user agent either has no knowledge of the geometry of physical pixels, or knows about the geometry physical pixels and they are (close enough to) square, it would not map a different number of device pixels per css pixels along each axis, and the would therefore be no difference between the vertical and horizontal resolution.
Otherwise, if the UA choses to map a different number along each axis, this would be to respond to physical pixels not being square either. How the UA comes to this knowledge is out of scope, but having enough information to take this decision, it can invert the mapping should the device be rotated 90 degrees.
5.2. Screen Display Type: the scan feature
Name: | scan |
---|---|
For: | @media |
Value: | interlace | progressive |
Type: | discrete |
The scan media feature describes the scanning process of some output devices.
- interlace
-
CRT and some types of plasma TV screens used “interlaced” rendering,
where video frames alternated between specifying only the “even” lines on the screen
and only the “odd” lines,
exploiting various automatic mental image-correction abilities to produce smooth motion.
This allowed them to simulate a higher FPS broadcast at half the bandwidth cost.
When displaying on interlaced screens, authors should avoid very fast movement across the screen to avoid “combing”, and should ensure that details on the screen are wider than 1px to avoid “twitter”.
- progressive
-
A screen using “progressive” rendering displays each screen fully,
and needs no special treatment.
Most modern screens, and all computer screens, use progressive rendering.
@media (scan: interlace) { body { font-family: sans-serif; } }
5.3. Detecting Console Displays: the grid feature
Name: | grid |
---|---|
For: | @media |
Value: | <mq-boolean> |
Type: | discrete |
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.
The <mq-boolean> value type is an <integer> with the value 0 or 1. Any other integer value is invalid. Note that -0 is always equivalent to 0 in CSS, and so is also accepted as a valid <mq-boolean> value.
Note: The <mq-boolean> type exists only for legacy purposes. If this feature were being designed today, it would instead use proper named keywords for its values.
5.4. Screen Update Frequency: the update feature
Name: | update |
---|---|
For: | @media |
Value: | none | slow | fast |
Type: | discrete |
The update media feature is used to query the ability of the output device to modify the apearance of content once it has been rendered. It accepts the following values:
- none
- Once it has been rendered, the layout can no longer be updated. Example: documents printed on paper.
- slow
- The layout may change dynamically according to the usual rules of CSS, but the output device is not able to render or display changes quickly enough for them to be percieved as a smooth animation. Example: E-ink screens or severely under-powered devices.
- fast
- The layout may change dynamically according to the usual rules of CSS, and the output device is not unusually constrained in speed, so regularly-updating things like CSS Animations can be used. Example: computer screens.
@media (update) { a { text-decoration: none; } a:hover, a:focus { text-decoration: underline; } } /* In non-updating UAs, the links get their default underline at all times. */
5.5. Block-Axis Overflow: the overflow-block feature
Name: | overflow-block |
---|---|
For: | @media |
Value: | none | scroll | optional-paged | paged |
Type: | discrete |
The overflow-block media feature describes the behavior of the device when content overflows the initial containing block in the block axis.
- none
- There is no affordance for overflow in the block axis; any overflowing content is simply not displayed. Examples: billboards
- scroll
- Overflowing content in the block axis is exposed by allowing users to scroll to it. Examples: computer screens
- optional-paged
- Overflowing content in the block axis is exposed by allowing users to scroll to it, but page breaks can be manually triggered (such as via break-inside/etc) to cause the following content to display on the following page. Examples: slideshows
- paged
- Content is broken up into discrete pages; content that overflows one page in the block axis is displayed on the following page. Examples: printers, ebook readers
5.6. Inline-Axis Overflow: the overflow-inline feature
Name: | overflow-inline |
---|---|
For: | @media |
Value: | none | scroll |
Type: | discrete |
The overflow-inline media feature describes the behavior of the device when content overflows the initial containing block in the inline axis.
- none
- There is no affordance for overflow in the inline axis; any overflowing content is simply not displayed.
- scroll
- Overflowing content in the inline axis is exposed by allowing users to scroll to it.
Note: There are no known implementations of paged overflow of inline-overflowing content, and the very concept doesn’t seem to make much sense, so there is intentionally no paged value for overflow-inline.
6. Color Media Features
6.1. Screen Color Depth: the color feature
Name: | color |
---|---|
For: | @media |
Value: | <integer> |
Type: | range |
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.
Negative <integer>s are invalid.
@media (color) { … } @media (min-color: 1) { … }
@media (color >= 8) { … }
If different color components are represented by different number of bits, the smallest number is used.
In a device with indexed colors, the minimum number of bits per color component in the lookup table is used.
Note: 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.
6.2. Paletted Color Screens: the color-index feature
Name: | color-index |
---|---|
For: | @media |
Value: | <integer> |
Type: | range |
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.
Negative <integer>s are invalid.
@media (color-index) { … } @media (color-index >= 1) { … }
<?xml-stylesheet media="(min-color-index: 256)" href="http://www.example.com/…" ?>
6.3. Monochrome Screens: the monochrome feature
Name: | monochrome |
---|---|
For: | @media |
Value: | <integer> |
Type: | range |
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.
Negative <integer>s are invalid.
@media (monochrome) { … }
@media (monochrome >= 2) { … }
<link rel="stylesheet" media="print and (color)" href="http://…" /> <link rel="stylesheet" media="print and (monochrome)" href="http://…" />
6.4. Color Display Quality: the color-gamut feature
Name: | color-gamut |
---|---|
For: | @media |
Value: | srgb | p3 | rec2020 |
Type: | discrete |
The color-gamut media feature describes the approximate range of colors that are supported by the UA and output device. That is, if the UA receives content with colors in the specified space it can cause the output device to render the appropriate color, or something appropriately close enough.
Note: The query uses approximate ranges for a few reasons. Firstly, there are a lot of differences in display hardware. For example, a device might claim to support "Rec 2020", but actually renders a significantly lower range of the full gamut. Secondly, there are a lot of different color ranges that different devices support, and enumerating them all would be tedious. In most cases the author does not need to know the exact capabilities of the display, just whether it is better than sRGB, or significantly better than sRGB. That way they can serve appropriate images, tagged with color profiles, to the user.
- srgb
-
The output device can support approximately the sRGB gamut [SRGB] or more.
Note: It is expected that the vast majority of color displays will be able to return true to a query of this type.
- p3
-
The output device can support approximately the gamut
specified by the DCIP3 Color Space or more.
Note: The p3 gamut is larger than and includes the srgb gamut.
- rec2020
-
The output device can support approximately the gamut
specified by the ITU-R Recommendation BT.2020 Color Space or more.
Note: The rec2020 gamut is larger than and includes the p3 gamut.
@media (color-gamut: p3) { … }
Note: An output device can return true for multiple values of this media feature,
if its full output gamut is large enough,
or one gamut is a subset of another supported gamut.
As a result,
this feature is best used in an "ascending" fashion—
Note: Some output devices, such as monochrome displays, cannot support even the srgb gamut. To test for these devices, you can use this feature in a negated boolean-context fashion: not (color-gamut).
Or should we add a value specifically for the "less than sRGB" case, like narrow? It would have to work differently than the others, and only match if the gamut was extra-low.
7. Interaction Media Features
The “interaction” media features reflect various aspects of how the user interacts with the page.
pointer: coarse | pointer: fine | |
---|---|---|
hover: none | smartphones, touch screens | stylus-based screens (Cintiq, Wacom, etc) |
hover: hover | Nintendo Wii controller, Kinect | mouse, touch pad |
7.1. Pointing Device Quality: the pointer feature
Name: | pointer |
---|---|
For: | @media |
Value: | none | coarse | fine |
Type: | discrete |
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, the pointer media feature must reflect the characteristics of the “primary” input mechanism, as determined by the user agent. (To query the capabilities of any available input mechanism, see the any-pointer media feature.)
- none
- The primary input mechanism of the device does not include a pointing device.
- coarse
- The primary input mechanism of the device includes a pointing device of limited accuracy. Examples include touchscreens and motion-detection sensors (like the Kinect peripheral for the Xbox.)
- fine
- The primary input mechanism of the device includes an accurate pointing device. Examples include mice, touchpads, and drawing styluses.
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 at a zoom factor of 1 would qualify as coarse. Changing the zoom level does not affect the value of this media feature.
Note: As the UA may provide the user with the ability to zoom, or as secondary pointing devices may have a different accuracy, the user may be able to perform accurate clicks even if the value of this media feature is coarse. This media feature does not indicate that the user will never be able to click accurately, only that it is inconvenient for them to do so. Authors are expected to react to a value of coarse by designing pages that do not rely on accurate clicking to be operated.
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 pointing 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-width:30px; min-height:40px; background:transparent; } }
7.2. Hover Capability: the hover feature
Name: | hover |
---|---|
For: | @media |
Value: | none | hover |
Type: | discrete |
The hover media feature is used to query the user’s ability to hover over elements on the page. If a device has multiple input mechanisms, the hover media feature must reflect the characteristics of the “primary” input mechanism, as determined by the user agent. (To query the capabilities of any available input mechanism, see the any-hover media feature.)
- none
-
Indicates that the primary pointing system can’t hover,
or there is no pointing system.
Examples include touchscreens and screens that use a drawing stylus.
Pointing systems that can hover, but for which doing so is inconvenient and not part of the normal way they are used, also match this value. For example, a touchscreen where a long press is treated as hovering would match hover: none.
- hover
- Indicates that the primary pointing system can easily hover over parts of the page. Examples include mice and devices that physically point at the screen, like the Nintendo Wii controller.
Authors should therefore be careful not to assume that the ':hover' pseudo class will never match on device where 'hover:none' is true, but they should design layouts that do not depend on hovering to be fully usable.
For accessibility reasons, even on devices that do support hovering, the UA may give a value of hover: none to this media query, to opt into layouts that work well without hovering.
/* Only use a hover-activated drop down menu on devices that can conveniently hover. */ @media (hover) { .menu > li {display:inline-block;} .menu ul {display:none; position:absolute;} .menu li:hover ul {display:block; list-style:none; padding:0;} /* ... */ }
7.3. Rare Interaction Capabilities: the any-pointer and any-hover features
Name: | any-pointer |
---|---|
For: | @media |
Value: | none | coarse | fine |
Type: | discrete |
Name: | any-hover |
---|---|
For: | @media |
Value: | none | hover |
Type: | discrete |
The any-pointer and any-hover media features are identical to the pointer and hover media features, but they correspond to the union of capabilities of all the pointing devices available to the user. More than one of their values can match, if different pointing devices have different characteristics. They must only match none if all of the pointing devices would match none for the corresponding query, or there are no pointing devices at all.
Designing a page that relies on hovering or accurate pointing only because any-hover or any-pointer indicate that an input mechanism with these capabilities is available, is likely to result in a poor experience.
A browser in such a smart TV would have coarse as the value of both pointer and any-pointer, allowing authors to provide a layout with large and easy to reach click targets.
The user may also have paired a Bluetooth mouse with the TV, and occasionally use it for extra convenience, but such the mouse is not the main way the TV is operated. pointer still matches coarse, while any-pointer now both matches coarse and fine.
Switching to small click targets based on the fact that (any-pointer: fine) is now true would not be appropriate. It would not only surprise the user by providing an experience out of line with what they expect on a TV, but may also be quite inconvenient: the mouse, not being the primary way to control the TV, may be out of reach, hidden under one of the cushions on the sofa...
By contrast, consider scrolling on the same TV. Scrollbars are difficult to manipulate without an accurate pointing device. Having prepared an alternative way to indicate that there is more content to be seen based on (pointer: coarse) being true, an author may want to still show the scrollbars in addition if (any-pointer: fine) is true, or to hide them altogether to reduce visual clutter if (any-pointer: fine) is false.
8. Scripting Media Features
8.1. Scripting Support: the scripting feature
Name: | scripting |
---|---|
For: | @media |
Value: | none | initial-only | enabled |
Type: | discrete |
The scripting media feature is used to query whether scripting languages, such as JavaScript, are supported on the current document.
- enabled
- Indicates that the user agent supports scripting of the page and that support is active for the current document.
- initial-only
-
Indicates that scripting is enabled during the initial page load,
but is not supported afterwards.
Examples are printed pages,
or pre-rendering network proxies
that render a page on a server
and send a nearly-static version of the page to the user.
Should there be an explicit minimum threshold to meet before a UA is allowed to claim initial-only? Having one would mean authors would know what they can depend on, and could tailor their scripts accordingly. On the other hand, pinpointing that threshold is difficult: if it is set too low, the scripting facilities that authors can depend on may be to constrained to be practical, even though actual UAs may potentially all support significantly more. But trying to set it higher may cause us to exclude UAs that do support scripting at loading time, but restrict it in some cases based on complex heuristics. For instance, conservative definitions likely include at least running all inline scripts and firing the DOMContentLoaded event. But it does not seem useful for authors to constrain themselves to this if most (or maybe all) initial-only UAs also load external scripts (including async and defer) and fire the load event. On the other hand, requiring external scripts to be loaded and the load event to be fired could exclude UAs like Opera mini, which typically do run them, but may decide not to based on timeouts and other heuristics.
- none
- Indicates that the user agent will not run scripts for this document; either it doesn’t support a scripting language, or the support isn’t active for the current document.
Some user agents have the ability to turn off scripting support on a per script basis or per domain basis, allowing some, but not all, scripts to run in a particular document. The scripting media feature does not allow fine grained detection of which script is allowed to run. In this scenario, the value of the scripting media feature should be enabled if scripts originating on the same domain as the document are allowed to run, and none otherwise.
Note: A future level of CSS may extend this media feature to allow fine-grained detection of which script is allowed to run.
9. Appendix A: Deprecated Media Features
The following media features are deprecated. They kept for backward compatibility, but are not appropriate for newly written style sheets. Authors must not use them. User agents must support them as specified.
To query for the size of the viewport (or the page box on page media), the width, height and aspect-ratio media features should be used, rather than device-width, device-height and device-aspect-ratio, which refer to the physical size of the the device regardless of how much space is available for the document being laid out. The device-* media features are also sometimes used as a proxy to detect mobile devices. Instead, authors should use media features that better represent the aspect of the device that they are attempting to style against.
device-width
Name: | device-width |
---|---|
For: | @media |
Value: | <length> |
Type: | range |
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.
Negative <length>s are invalid.
@media (device-width < 800px) { … }
In the example above, the style sheet will apply only to screens less than 800px in length. The px unit is of the logical kind, as described in the Units section.
Note: If a device can be used in multiple orientations, such as portrait and landscape, the device-* media features reflect the current orientation.
device-height
Name: | device-height |
---|---|
For: | @media |
Value: | <length> |
Type: | range |
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.
Negative <length>s are invalid.
<link rel="stylesheet" media="(device-height > 600px)" />
In the example above, the style sheet will apply only to screens taller than 600 vertical pixels. Note that the definition of the px unit is the same as in other parts of CSS.
device-aspect-ratio
Name: | device-aspect-ratio |
---|---|
For: | @media |
Value: | <ratio> |
Type: | range |
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.
@media (device-aspect-ratio: 16/9) { … } @media (device-aspect-ratio: 32/18) { … } @media (device-aspect-ratio: 1280/720) { … } @media (device-aspect-ratio: 2560/1440) { … }
Changes
Changes Since the Media Queries Level 3
The following changes were made to this specification since the 19 June 2012 Recomendation of Media Queries Level 3:
- Large editorial rewrite and reorgization of the document.
- Boolean-context media features are now additionally false if they would be true for the keyword none.
- Media features with numeric values can now be written in a range context.
- The scripting, pointer, hover, update, overflow-block, and overflow-inline media features were added.
- or, and, only and not are disallowed from being recognized as media types, even invalid ones. (They’ll trigger a syntax error instead.)
- White space is required around the keyword “and” as well as after “not” and “only”.
- All media types except for screen, print, speech, and all are deprecated.
- Deprecated device-width, device-height, device-aspect-ratio
Acknowledgments
This specification is the product of the W3C Working Group on Cascading Style Sheets.
Comments from Arve Bersvendsen, Björn Höhrmann, Chris Lilley, Christoph Päper, L. David Baron, Elika J. Etemad, François Remy, Melinda Grant, Nicholas C. Zakas Philipp Hoschka, Rick Byers, Rijk van Geijtenbeek, Roger Gimson, Sigurd Lerstad, Simon Kissane, Simon Pieters, Steven Pemberton, and Susan Lesch improved this specification.
10. Privacy and Security Considerations
This specification introduces no new security considerations.
Media Queries enable CSS to query various aspects of the page’s environment, including things that can be difficult or impossible to find via scripting. This is potentially a privacy hazard, allowing enhanced fingerprinting of a user, but the risk is generally low. At minimum, the same information should be inferrable via scripting by examining the User Agent string. However, UA string spoofing does not affect Media Queries, making this a somewhat more robust detection technique.
That said, the information granted by Media Queries is relatively coarse, and does not contribute much entropy in this regard.