Internet technology hosted by Berkman Center
RSS 2.0 Specification
Tuesday, July 15, 2003
- What is RSS?
- Sample files
- About this document
- Required channel elements
- Optional channel elements
- Elements of
- Extending RSS
- License and authorship
What is RSS?
RSS is a Web content syndication format.
Its name is an acronym for Really Simple Syndication.
RSS is a dialect of XML. All RSS files must conform to the XML 1.0 specification, as published on the World Wide Web Consortium (W3C) website.
A summary of RSS version history.
At the top level, a RSS document is a
Subordinate to the
Here are sample files for: RSS 0.91, 0.92 and 2.0.
Note that the sample files may point to documents and services that no longer exist. The 0.91 sample was created when the 0.91 docs were written. Maintaining a trail of samples seems like a good idea.
About this document
This document represents the status of RSS as of the Fall of 2002, version 2.0.1.
It incorporates all changes and additions, starting with the basic spec for RSS 0.91 (June 2000) and includes new features introduced in RSS 0.92 (December 2000) and RSS 0.94 (August 2002).
Change notes are here.
First we document the required and optional sub-elements of
Required channel elements
Here’s a list of the required channel elements, each with a brief description, an example, and where available, a pointer to a more complete description.
|title||The name of the channel. It’s how people refer to your service. If you have an HTML website that contains the same information as your RSS file, the title of your channel should be the same as the title of your website.||GoUpstate.com News Headlines|
|link||The URL to the HTML website corresponding to the channel.||http://www.goupstate.com/|
|description||Phrase or sentence describing the channel.||The latest news from GoUpstate.com, a Spartanburg Herald-Journal Web site.|
Optional channel elements
Here’s a list of optional channel elements.
|language||The language the channel is written in. This allows aggregators to group all Italian language sites, for example, on a single page. A list of allowable values for this element, as provided by Netscape, is here. You may also use values defined by the W3C.||en-us|
|copyright||Copyright notice for content in the channel.||Copyright 2002, Spartanburg Herald-Journal|
|managingEditor||Email address for person responsible for editorial email@example.com (George Matesky)|
|webMaster||Email address for person responsible for technical issues relating to firstname.lastname@example.org (Betty Guernsey)|
|pubDate||The publication date for the content in the channel. For example, the New York Times publishes on a daily basis, the publication date flips once every 24 hours. That’s when the pubDate of the channel changes. All date-times in RSS conform to the Date and Time Specification of RFC 822, with the exception that the year may be expressed with two characters or four characters (four preferred).||Sat, 07 Sep 2002 00:00:01 GMT|
|lastBuildDate||The last time the content of the channel changed.||Sat, 07 Sep 2002 09:42:31 GMT|
|category||Specify one or more categories that the channel belongs to. Follows the same rules as the
|generator||A string indicating the program used to generate the channel.||MightyInHouse Content System v2.3|
|docs||A URL that points to the documentation for the format used in the RSS file. It’s probably a pointer to this page. It’s for people who might stumble across an RSS file on a Web server 25 years from now and wonder what it is.||http://blogs.law.harvard.edu/tech/rss|
|cloud||Allows processes to register with a cloud to be notified of updates to the channel, implementing a lightweight publish-subscribe protocol for RSS feeds. More info here.|
|ttl||ttl stands for time to live. It’s a number of minutes that indicates how long a channel can be cached before refreshing from the source. More info here.|
|image||Specifies a GIF, JPEG or PNG image that can be displayed with the channel. More info here.|
|rating||The PICS rating for the channel.|
|textInput||Specifies a text input box that can be displayed with the channel. More info here.|
|skipHours||A hint for aggregators telling them which hours they can skip. More info here.|
|skipDays||A hint for aggregators telling them which days they can skip. More info here.|
is an optional sub-element of
is the URL of the site, when the channel is rendered, the image is a link to the site. (Note, in practice the image
Optional elements include
Maximum value for width is 144, default value is 88.
Maximum value for height is 400, default value is 31.
It specifies a web service that supports the rssCloud interface which can be implemented in HTTP-POST, XML-RPC or SOAP 1.1.
Its purpose is to allow processes to register with a cloud to be notified of updates to the channel, implementing a lightweight publish-subscribe protocol for RSS feeds.
In this example, to request notification on the channel it appears in, you would send an XML-RPC message to rpc.sys.com on port 80, with a path of /RPC2. The procedure to call is myCloud.rssPleaseNotify.
A full explanation of this element and the rssCloud interface is here.
ttl stands for time to live. It’s a number of minutes that indicates how long a channel can be cached before refreshing from the source. This makes it possible for RSS sources to be managed by a file-sharing network such as Gnutella.
A channel may optionally contain a
— The URL of the CGI script that processes text input requests.
The purpose of the
A channel may contain any number of
|title||The title of the item.||Venice Film Festival Tries to Quit Sinking|
|link||The URL of the item.||http://nytimes.com/2004/12/07FEST.html|
|description||The item synopsis.||Some of the most heated chatter at the Venice Film Festival this week was about the way that the arrival of the stars at the Palazzo del Cinema was being staged.|
|author||Email address of the author of the item. More.||email@example.com|
|category||Includes the item in one or more categories. More.|
|comments||URL of a page for comments relating to the item. More.||http://www.myblog.org/cgi-local/mt/mt-comments.cgi?entry_id=290|
|enclosure||Describes a media object that is attached to the item. More.|
|guid||A string that uniquely identifies the item. More.||http://inessential.com/2002/09/01.php#a2|
|pubDate||Indicates when the item was published. More.||Sun, 19 May 2002 15:21:36 GMT|
|source||The RSS channel that the item came from. More.|
Its value is the name of the RSS channel that the item came from, derived from its
The purpose of this element is to propagate credit for links, to publicize the sources of news items. It can be used in the Post command of an aggregator. It should be generated automatically when forwarding an item from an aggregator to a weblog authoring tool.
It has three required attributes. url says where the enclosure is located, length says how big it is in bytes, and type says what its type is, a standard MIME type.
The url must be an http url.
A use-case narrative for this element is here.
It has one optional attribute, domain, a string that identifies a categorization taxonomy.
The value of the element is a forward-slash-separated string that identifies a hierarchic location in the indicated taxonomy. Processors may establish conventions for the interpretation of categories. Two examples are provided below:
You may include as many category elements as you need to, for different domains, and to have an item cross-referenced in different parts of the same domain.
Its value is a date, indicating when the item was published. If it’s a date in the future, aggregators may choose to not display the item until that date.
guid stands for globally unique identifier. It’s a string that uniquely identifies the item. When present, an aggregator may choose to use this string to determine if an item is new.
There are no rules for the syntax of a guid. Aggregators must view them as a string. It’s up to the source of the feed to establish the uniqueness of the string.
If the guid element has an attribute named “isPermaLink” with a value of true, the reader may assume that it is a permalink to the item, that is, a url that can be opened in a Web browser, that points to the full item described by the
isPermaLink is optional, its default value is true. If its value is false, the guid may not be assumed to be a url, or a url to anything in particular.
If present, it is the url of the comments page for the item.
More about comments here.
is an optional sub-element of
It’s the email address of the author of the item. For newspapers and magazines syndicating via RSS, the author is the person who wrote the article that the
RSS places restrictions on the first non-whitespace characters of the data in and
In RSS 0.91, various elements are restricted to 500 or 100 characters. There can be no more than 15
In RSS 2.0, a provision is made for linking a channel to its identifier in a cataloging system, using the channel-level category feature, described above. For example, to link a channel to its Syndic8 identifier, include a category element as a sub-element of
A frequently asked question about
If you have questions about the RSS 2.0 format, please post them on the RSS2-Support mail list, hosted by Sjoerd Visscher. This is not a debating list, but serves as a support resource for users, authors and developers who are creating and using content in RSS 2.0 format.
RSS originated in 1999, and has strived to be a simple, easy to understand format, with relatively modest goals. After it became a popular format, developers wanted to extend it using modules defined in namespaces, as specified by the W3C.
RSS 2.0 adds that capability, following a simple rule. A RSS feed may contain elements not described on this page, only if those elements are defined in a namespace.
The elements defined in this document are not themselves members of a namespace, so that RSS 2.0 can remain compatible with previous versions in the following sense — a version 0.91 or 0.92 file is also a valid 2.0 file. If the elements of RSS 2.0 were in a namespace, this constraint would break, a version 0.9x file would not be a valid 2.0 file.
RSS is by no means a perfect format, but it is very popular and widely supported. Having a settled spec is something RSS has needed for a long time. The purpose of this work is to help it become a unchanging thing, to foster growth in the market that is developing around it, and to clear the path for innovation in new syndication formats. Therefore, the RSS spec is, for all practical purposes, frozen at version 2.0.1. We anticipate possible 2.0.2 or 2.0.3 versions, etc. only for the purpose of clarifying the specification, not for adding new features to the format. Subsequent work should happen in modules, using namespaces, and in completely new syndication formats, with new names.
License and authorship
RSS 2.0 is offered by the Berkman Center for Internet & Society at Harvard Law School under the terms of the Attribution/Share Alike Creative Commons license. The author of this document is Dave Winer, founder of UserLand software, and fellow at Berkman Center.