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 (literary theory), writing, Sound, audio, images, animations, or video, into a single presentation. T ...
content to
RSS
RSS ( RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many ...
feeds with the purpose of allowing that content to be
prefetched. Enclosures provide the
URL
A uniform resource locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identi ...
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 under the lead of Karlheinz Brandenburg. It was designed to greatly reduce the amount ...
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 providing direct access to Data (computing), data by a user (computing), user's point and click, clicking or touchscreen, tapping. A hyperlink points to a whole document or to ...
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 Computer standard, 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 format, pr ...
, 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 systems. 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 service ...
in late 200
was an important prerequisite for the emergence of
podcast
A podcast is a Radio program, program made available in digital format for download over the Internet. Typically, a podcast is an Episode, episodic series of digital audio Computer file, files that users can download to a personal device or str ...
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
A uniform resource locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identi ...
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 un ...
s, and ''type'' its mime type
In information and communications technology, a media type, content type or MIME type is a two-part identifier for file formats and content formats. Their purpose is comparable to filename extensions and uniform type identifiers, in that they ide ...
.
It is recommended that only one element is included per
Prefetching
The RSS <enclosure> has similarities to:
* the SMIL <prefetch> element,
* the HTML
Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It defines the content and structure of web content. It is often assisted by technologies such as Cascading Style Sheets ( ...
<link> element with rel="prefetch
* the HTTP
HTTP (Hypertext Transfer Protocol) 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 Web, wher ...
Link header with rel="prefetch". (See section 19.6.2.4.)
* the Atom
Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...
<link> element with rel="enclosure"
See also
* Broadcatching
* Internet television
Streaming television is the digital distribution of television content, such as films and television show, television series, Streaming media, streamed over the Internet. Standing in contrast to dedicated terrestrial television delivered by Broadc ...
* Podcast
A podcast is a Radio program, program made available in digital format for download over the Internet. Typically, a podcast is an Episode, episodic series of digital audio Computer file, files that users can download to a personal device or str ...
* Photofeed
* Vlog
A vlog (), also known as a video blog or video log, 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 in one ta ...
References
External links
The tag in the RSS 2.0 specification
- Enclosures in RSS 1.x
Enclosure intended use case
{{Web syndication
RSS
Web syndication formats
XML-based standards