previous(cascade)   next(box)   contents   properties   index

7 Media types


7.1 Introduction to media types

One of the most important features of style sheets is that they specify how a document is to be presented on different media: on the screen, on paper, with a speech synthesizer, with a braille device, etc.

Certain CSS properties are only designed for certain media (e.g., the 'cue-before' property for aural user agents). On occasion, however, style sheets for different media types may share a property, but require different values for that property. For example, the 'font-size' property is useful both for screen and print media. However, the two media are different enough to require different values for the common property; a document will typically need a larger font on a computer screen than on paper. Experience also shows that sans-serif fonts are easier to read on screen, while fonts with serifs are easier to read on paper. For these reasons, it is necessary to express that a style sheet -- or a section of a style sheet -- applies to certain media types.

7.2 Specifying media-dependent style sheets

There are currently two ways to specify media dependencies for style sheets:

The @import rule is defined in the chapter on the cascade.

7.2.1 The @media rule

An @media rule specifies the target media types (separated by commas) of a set of rules (delimited by curly braces). The @media construct allows style sheet rules for various media in the same style sheet:

  @media print {
    BODY { font-size: 10pt }
  @media screen {
    BODY { font-size: 12pt }
  @media screen, print {
    BODY { line-height: 1.2 }

7.3 Recognized media types

A CSS media type names a set of CSS properties. A user agent that claims to support a media type by name must implement all of the properties that apply to that media type.

The names chosen for CSS media types reflect target devices for which the relevant properties make sense. In the following list of CSS media types, the parenthetical descriptions are not normative. They only give a sense of what device the media type is meant to refer to.

Suitable for all devices.
Intended for speech synthesizers. See the section on aural style sheets for details.
Intended for braille tactile feedback devices.
Intended for paged braille printers.
Intended for handheld devices (typically small screen, monochrome, limited bandwidth).
Intended for paged, opaque material and for documents viewed on screen in print preview mode. Please consult the section on paged media for information about formatting issues that are specific to paged media.
Intended for projected presentations, for example projectors or print to transparencies. Please consult the section on paged media for information about formatting issues that are specific to paged media.
Intended primarily for color computer screens.
Intended for media using a fixed-pitch character grid, such as teletypes, terminals, or portable devices with limited display capabilities. Authors should not use pixel units with the "tty" media type.
Intended for television-type devices (low resolution, color, limited-scrollability screens, sound available).

Media type names are case-insensitive.

Due to rapidly changing technologies, CSS2 does not specify a definitive list of media types that may be values for @media.

Note. Future versions of CSS may extend this list. Authors should not rely on media type names that are not yet defined by a CSS specification.

7.3.1 Media groups

Each CSS property definition specifies the media types for which the property must be implemented by a conforming user agent. Since properties generally apply to several media, the "Applies to media" section of each property definition lists media groups rather than individual media types. Each property applies to all media types in the media groups listed in its definition.

CSS2 defines the following media groups:

The following table shows the relationships between media groups and media types:

Relationship between media groups and media types
Media Groups
aural continuous auralN/Ainteractive
braille continuous tactilegridinteractive
emboss paged tactilegridinteractive
handheldboth visualbothinteractive
print paged visualbitmap 
projectionpaged visualbitmap 
screen continuous visualbitmapinteractive
tty continuous visualgridinteractive
tv both visual, auralbitmapinteractive