RSS enclosures are a way of attaching multimedia content to RSS feeds with the purpose of allowing that content to be prefetched. Enclosures provide the URL of a file associated with an entry, such as an MP3 file to a music recommendation or a photo to a diary entry. Unlike e-mail attachments, enclosures are merely hyperlinks to files. The actual file data is not embedded into the feed (unless a data URL is used). Support and implementation among aggregatorss varies: if the software understands the specified file format, it may automatically download 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 in late 2000 http://backend.userland.com/rss092, was an important prerequisite for the emergence of podcasting, 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 <enclosure> tag, an optional child of the <item> element, is as follows:

<enclosure url="http://example.com/file.mp3" length="123456789" type="audio/mpeg" />

where the value of the url attribute is a URL of a file, length is its size in bytes, and type its mime type.

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Prefetching

The RSS enclosure has similarities to:

• the SMIL prefetch element,

• the HTML link element with rel="prefetch".https://www.mozilla.org/projects/netlib/Link_Prefetching_FAQ.html

• the HTTP Link header with rel="prefetch". (See section 19.6.2.4.)

• the Atom link element with rel="enclosure"

See also

• Broadcatching

• Internet television

• Podcast

• Photofeed

• Vlog

References

External links

• The <enclosure> tag in the RSS 2.0 specification

• mod_enclosure - Enclosures in RSS 1.x

• Enclosure intended use case