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''page-break-before' property for aural user agents).only applies to paged media). 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 types 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,Therefore, it is necessary to express that a style sheet --sheet, or a section of a style sheet --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:  12pt13px }
  @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,types the names of media types are normative, but the parentheticaldescriptions are not normative. They only give a sense of what deviceinformative. Likewise, the media type"Media" field in the description of each property is meant to refer to.informative.

Suitable for all devices.
aural Intended for speech synthesizers. See the section on aural style sheets for details.braille
Intended for braille tactile feedback devices.
Intended for paged braille printers.
Intended for handheld devices (typically small screen, monochrome,limited bandwidth).
Intended for paged, opaquepaged 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.projectors. 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 speech synthesizers. Note: CSS2 had a similar media type called 'aural' for this purpose. See the appendix on aural style sheets for details.
Intended for media using a fixed-pitch character grid, suchgrid (such as teletypes, terminals, or portable devices with limited display capabilities.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 ofMedia types are mutually exclusive in the sense that a user agent can only support one media type when rendering a document. However, user agents may be values forhave different modes which support different media types.

Unknown media type names should not result in the @media .rule being ignored.

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

7.3.1 Media groups

This section is informative, not normative.

Each CSS property definition specifies thewhich media types for whichthe property must be implemented by a conforming user agent .applies to. Since properties generally apply to several media,media types, 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.

CSS2CSS 2.1 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 Types Media Groups
  continuous/paged visual/aural/tactilevisual/audio/speech/tactile grid/bitmap interactive/static
aural continuous aural N/A bothbraillecontinuoustactilegridboth
embossembossedpagedtactilegrid bothstatic
handheldboth visualvisual, audio, speechbothboth
projectionpagedvisualbitmap staticinteractive
screencontinuous visualvisual, audiobitmapboth
tvbothvisual, auralaudiobitmapboth