RSS enclosures are a way of attaching
multimedia
Multimedia is a form of communication that uses a combination of different content forms such as text, audio, images, animations, or video into a single interactive presentation, in contrast to tradit ...
content to
RSS feeds by providing the
URL of a file associated with an entry, such as an
MP3
MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...
file to a music recommendation or a photo to a diary entry. Unlike
e-mail attachments, enclosures are merely
hyperlink
In computing, a hyperlink, or simply a link, is a digital reference to data that the user can follow or be guided by clicking or tapping. A hyperlink points to a whole document or to a specific element within a document. Hypertext is text w ...
s to files. The actual file data is not
embedded into the feed (unless a
data URL is used). Support and implementation among
aggregators varies: if the software understands the specified
file format
A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free.
Some file format ...
, it may automatically
download
In computer networks, download means to ''receive'' data from a remote system, typically a server such as a web server, an FTP server, an email server, or other similar system. This contrasts with uploading, where data is ''sent to'' a remote ...
and display the content, otherwise provide a link to it or silently ignore it.
The addition of enclosures to RSS, as first implemented by
Dave Winer
Dave Winer (born May 2, 1955, in Queens, New York City) is an American software developer, entrepreneur, and writer who resides in New York City. Winer is noted for his contributions to outliners, scripting, content management, and web servi ...
in late 200
was an important prerequisite for the emergence of
podcast
A podcast is a program made available in digital format for download over the Internet. For example, an episodic series of digital audio or video files that a user can download to a personal device to listen to at a time of their choosin ...
ing, perhaps the most common use of the feature . In podcasts and related technologies enclosures are not merely attachments to entries, but provide the main content of a feed.
Syntax
In RSS 2.0, the syntax for the
tag, an optional child of the - element, is as follows:
where the value of the ''url'' attribute is a URL of a file, ''length'' is its size in
byte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...
s, and ''type'' its mime type
A media type (also known as a MIME type) is a two-part identifier for file formats and format contents transmitted on the Internet. The Internet Assigned Numbers Authority (IANA) is the official authority for the standardization and publication o ...
.
It is recommended that only one element is included per
Prefetching
The RSS <enclosure> has similarities to:
* the SMIL <prefetch> element,
* the HTML
The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaS ...
<link> element with rel="prefetch
* the HTTP
The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide We ...
Link header with rel="prefetch". (See section 19.6.2.4.)
* the Atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, a ...
<link> element with rel="enclosure"
See also
* Broadcatching
Broadcatching is the downloading of digital content that has been made available over the Internet using RSS.
The general idea is to use an automated mechanism to aggregate various web feeds and download content for viewing or presentation purpose ...
* Internet television
Streaming television is the digital distribution of television content, such as TV shows, as streaming media delivered over the Internet. Streaming television stands in contrast to dedicated terrestrial television delivered by over-the-air ...
* Podcast
A podcast is a program made available in digital format for download over the Internet. For example, an episodic series of digital audio or video files that a user can download to a personal device to listen to at a time of their choosin ...
* Photofeed A photofeed is a web feed that features image enclosures. They provide an easy, standard way to reference a list of images with title, date and description.
Photofeeds are RSS enclosures of image file formats, similar to podcasts (enclosures of ...
* Vlog
A video blog or video log, sometimes shortened to vlog (), is a form of blog for which the medium is video. Vlog entries often combine embedded video (or a video link) with supporting text, images, and other metadata. Entries can be recorded i ...
References
External links
The tag in the RSS 2.0 specification
- Enclosures in RSS 1.x
RSS
Web syndication formats
XML-based standards
{{Podcasting-stub