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RSS ( RDF Site Summary or Really Simple Syndication) is a
web feed On the World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system An information system (IS) is a formal, sociotechnical Sociotechnical systems (STS) in organizational development is an approach to ...
that allows users and applications to access updates to websites in a
standardized Standardization or standardisation is the process of implementing and developing technical standard A technical standard is an established norm or requirement for a repeatable technical task. It is usually a formal document that establishes un ...
, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many different websites in a single
news aggregator In computing, a news aggregator, also termed a feed aggregator, feed reader, news reader, RSS reader or simply an aggregator, is client software or a web application that aggregates web syndication, syndicated web content such as online newspaper ...
, which constantly monitor sites for new content, removing the need for the user to manually check them. News aggregators (or "RSS readers") can be built into a browser, installed on a
desktop computer A desktop computer is a personal computer A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, ...
, or installed on a
mobile device A mobile device (or handheld computer) is a computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets ...
. Websites usually use RSS feeds to publish frequently updated information, such as
blog A blog (a truncation In mathematics and computer science, truncation is limiting the number of numerical digit, digits right of the decimal point. Truncation and floor function Truncation of positive real numbers can be done using the f ...
entries, news headlines, episodes of audio and video series, or for distributing . An RSS document (called "feed", "web feed", "Web feeds , RSS , The Guardian , guardian.co.uk", ''The Guardian'', London, 2008, webpage:
GuardianUK-webfeeds
or "channel") includes full or summarized text, and
metadata Metadata is "data Data (; ) are individual facts, statistics, or items of information, often numeric. In a more technical sense, data are a set of values of qualitative property, qualitative or quantity, quantitative variable (research), v ...

metadata
, like publishing date and author's name. RSS formats are specified using a generic
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
file. Although RSS formats have evolved from as early as March 1999, it was between 2005 and 2006 when RSS gained widespread use, and the ("") icon was decided upon by several major Web browsers. RSS feed data is presented to users using software called a
news aggregator In computing, a news aggregator, also termed a feed aggregator, feed reader, news reader, RSS reader or simply an aggregator, is client software or a web application that aggregates web syndication, syndicated web content such as online newspaper ...
and the passing of content is called
web syndication Web syndication is a form of syndication in which content is made available from one website A website (also written as web site) is a collection of web pages and related content that is identified by a common domain name and published on at ...
. Users subscribe to feeds either by entering a feed's
URI A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, concep ...
into the reader or by clicking on the browser's
feed icon On the World Wide Web upright=1.35, A global map of the web index for countries in 2014 The World Wide Web (WWW), commonly known as the Web, is an information system where documents and other web resources are identified by Uniform Res ...
. The RSS reader checks the user's feeds regularly for new information and can automatically download it, if that function is enabled.


History

The RSS formats were preceded by several attempts at
web syndication Web syndication is a form of syndication in which content is made available from one website A website (also written as web site) is a collection of web pages and related content that is identified by a common domain name and published on at ...
that did not achieve widespread popularity. The basic idea of restructuring information about websites goes back to as early as 1995, when Ramanathan V. Guha and others in
Apple An apple is an edible fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this fie ...
's Advanced Technology Group developed the Meta Content Framework. RDF Site Summary, the first version of RSS, was created by Dan Libby and Ramanathan V. Guha at
Netscape Netscape Communications Corporation (originally Mosaic Communications Corporation) was an American independent computer services company with headquarters in Mountain View, California Mountain View is a city in Santa Clara County, Californi ...

Netscape
. It was released in March 1999 for use on the My.Netscape.Com portal. This version became known as RSS 0.9. In July 1999, Dan Libby of Netscape produced a new version, RSS 0.91, which simplified the format by removing RDF elements and incorporating elements from
Dave Winer Dave Winer (born May 2, 1955 in Queens Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. It is the largest borough of New York City New York City (NYC), often simply called New York, ...
's news syndication format. Libby also renamed the format from RDF to RSS Rich Site Summary and outlined further development of the format in a "futures document". This would be Netscape's last participation in RSS development for eight years. As RSS was being embraced by web publishers who wanted their feeds to be used on My.Netscape.Com and other early RSS portals, Netscape dropped RSS support from My.Netscape.Com in April 2001 during new owner
AOL AOL (stylized as Aol., formerly a company known as AOL Inc. and originally known as America Online) is an American web portal A web portal is a specially designed website A website (also written as web site) is a collection of web page ...

AOL
's restructuring of the company, also removing documentation and tools that supported the format. Two parties emerged to fill the void, with neither Netscape's help nor approval: The
RSS-DEV Working GroupThe RSS-DEV Working Group was the outgrowth of a fork In cutlery or kitchenware:'' For a record label, see Kitchenware Records'' Kitchenware are the tools, kitchen utensil, utensils, Home appliance, appliances, Dishware, dishes, and cookware u ...
and
Dave Winer Dave Winer (born May 2, 1955 in Queens Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. It is the largest borough of New York City New York City (NYC), often simply called New York, ...
, whose
UserLand Software UserLand Software is a US-based software company, founded in 1988, that sells web content management, as well as blogging software packages and services. Company history Dave Winer founded the company in 1988 after leaving NortonLifeLock, Syman ...
had published some of the first publishing tools outside Netscape that could read and write RSS. Winer published a modified version of the RSS 0.91 specification on the UserLand website, covering how it was being used in his company's products, and claimed copyright to the document. A few months later, UserLand filed a U.S. trademark registration for RSS, but failed to respond to a
USPTO The United States Patent and Trademark Office (USPTO) is an agency in the U.S. Department of Commerce that issues patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, ...
trademark examiner's request and the request was rejected in December 2001. The RSS-DEV Working Group, a project whose members included
Aaron Swartz Aaron Hillel Swartz (November 8, 1986January 11, 2013) was an American computer programmer A computer programmer, sometimes called a software developer, a programmer or more recently a coder (especially in more informal contexts), is a pe ...

Aaron Swartz
, Guha and representatives of
O'Reilly Media O'Reilly Media (formerly O'Reilly & Associates) is an American learning company established by Tim O'Reilly Tim O'Reilly (born 6 June 1954) is the founder of O'Reilly Media O'Reilly Media (formerly O'Reilly & Associates) is an American l ...
and Moreover, produced RSS 1.0 in December 2000. This new version, which reclaimed the name RDF Site Summary from RSS 0.9, reintroduced support for RDF and added
XML namespace#REDIRECT XML namespace XML namespaces are used for providing uniquely named Data element, elements and attributes in an XML document. They are defined in a W3C recommendation. An XML instance may contain element or attribute names from more than one ...
s support, adopting elements from standard metadata vocabularies such as
Dublin Core file:DCMI-logo.svg, 220px, Logo image of DCMI, which formulates Dublin Core The Dublin Core, also known as the Dublin Core Metadata Element Set, is a set of fifteen "core" elements (properties) for describing resources. This fifteen-element Dublin ...
. In December 2000, Winer released RSS 0.92 a minor set of changes aside from the introduction of the enclosure element, which permitted audio files to be carried in RSS feeds and helped spark
podcast A podcast is an episodic series of digital audio Digital audio is a representation of sound recorded in, or converted into, Digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typical ...

podcast
ing. He also released drafts of RSS 0.93 and RSS 0.94 that were subsequently withdrawn. In September 2002, Winer released a major new version of the format, RSS 2.0, that redubbed its initials Really Simple Syndication. RSS 2.0 removed the ''type'' attribute added in the RSS 0.94 draft and added support for namespaces. To preserve backward compatibility with RSS 0.92, namespace support applies only to other content included within an RSS 2.0 feed, not the RSS 2.0 elements themselves. (Although other standards such as
Atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of ato ...
attempt to correct this limitation, RSS feeds are not aggregated with other content often enough to shift the popularity from RSS to other formats having full namespace support.) Because neither Winer nor the RSS-DEV Working Group had Netscape's involvement, they could not make an official claim on the RSS name or format. This has fueled ongoing controversy in the syndication development community as to which entity was the proper publisher of RSS. One product of that contentious debate was the creation of an alternative syndication format,
Atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of ato ...
, that began in June 2003. The Atom syndication format, whose creation was in part motivated by a desire to get a clean start free of the issues surrounding RSS, has been adopted as
IETF The Internet Engineering Task Force (IETF) is an open standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary functi ...
Proposed Standard . In July 2003, Winer and UserLand Software assigned the copyright of the RSS 2.0 specification to Harvard's
Berkman Klein Center for Internet & Society The Berkman Klein Center for Internet & Society is a research center at Harvard University that focuses on the study of cyberspace. Founded at Harvard Law School, the center traditionally focused on internet-related legal issues. On May 15, 2008, t ...
, where he had just begun a term as a visiting fellow. At the same time, Winer launched the
RSS Advisory BoardThe RSS Advisory Board is a group founded in July 2003 that publishes the RSS 0.9, RSS 0.91 and RSS 2.0 specifications and helps developers create RSS applications. Dave Winer, the lead author of several RSS specifications and a longtime evangelist ...
with
Brent Simmons NetNewsWire is a news aggregator for macOS and iOS. History NetNewsWire was developed by Brent and Sheila Simmons for their company Ranchero Software. It was introduced on July 12, 2002, with ''NetNewsWire Lite'', a free version missing some adva ...
and
Jon Udell Jon Udell Jon Udell is a freelance journalist. From 2007 to 2014 he was "Technology evangelist, Evangelist" at Microsoft. Previously he was lead analyst for the InfoWorld Test Center. Udell is author of ''Practical Internet Groupware'', published ...
, a group whose purpose was to maintain and publish the specification and answer questions about the format. In September 2004, Stephen Horlander created the now ubiquitous RSS icon () for use in the
Mozilla Mozilla (stylized as moz://a) is a free software Free software (or libre software) is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any a ...

Mozilla
Firefox Mozilla Firefox or simply Firefox is a free and open-source Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is free software license, freely licensed to use, copy, study, ...

Firefox
. In December 2005, the Microsoft Internet Explorer team and
Microsoft Outlook Microsoft Outlook is a personal information manager software system from Microsoft, available as a part of the Microsoft Office suite. Though primarily an email client, Outlook also includes such functions as Calendaring software, calendaring ...
team announced on their blogs that they were adopting Firefox's RSS icon. In February 2006,
Opera Software Opera is a Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in northwestern Europe *Norwegians, both a nation and an ethnic group native to Norway *Demographics of Norway *The Norwegian la ...

Opera Software
followed suit. This effectively made the orange square with white radio waves the industry standard for RSS and Atom feeds, replacing the large variety of icons and text that had been used previously to identify syndication data. In January 2006, Rogers Cadenhead relaunched the RSS Advisory Board without Dave Winer's participation, with a stated desire to continue the development of the RSS format and resolve ambiguities. In June 2007, the board revised their version of the specification to confirm that namespaces may extend core elements with namespace attributes, as Microsoft has done in Internet Explorer 7. According to their view, a difference of interpretation left publishers unsure of whether this was permitted or forbidden.


Example

RSS is
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
-formatted plain text. The RSS format itself is relatively easy to read both by automated processes and by humans alike. An example feed could have contents such as the following: RSS Title This is an example of an RSS feed http://www.example.com/main.html 2020 Example.com All rights reserved Mon, 06 Sep 2010 00:01:00 +0000 Sun, 06 Sep 2009 16:20:00 +0000 1800 Example entry Here is some text containing an interesting description. http://www.example.com/blog/post/1 7bd204c6-1655-4c27-aeee-53f933c5395f Sun, 06 Sep 2009 16:20:00 +0000


Aggregators

When retrieved, RSS reading software could use the XML structure to present a neat display to the end users. There are various news aggregator software for desktop and mobile devices, but RSS can also be built-in inside
web browser A web browser (commonly referred to as a browser) is application software for accessing the World Wide Web. When a User (computing), user requests a web page from a particular website, the web browser retrieves the necessary content from a web ...

web browser
s or
email client An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program In imperative programming, a computer program is a sequence of instructions in a programming language that a computer can execut ...
s like
Mozilla Thunderbird Mozilla Thunderbird is a free and open-source Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is free software license, freely licensed to use, copy, study, and change the sof ...
.


Variants

There are several different versions of RSS, falling into two major branches (RDF and 2.*). The RDF (or RSS 1.*) branch includes the following versions: *RSS 0.90 was the original Netscape RSS version. This RSS was called '' RDF Site Summary'', but was based on an early working draft of the RDF standard, and was not compatible with the final RDF Recommendation. *RSS 1.0 is an open format by the
RSS-DEV Working GroupThe RSS-DEV Working Group was the outgrowth of a fork In cutlery or kitchenware:'' For a record label, see Kitchenware Records'' Kitchenware are the tools, kitchen utensil, utensils, Home appliance, appliances, Dishware, dishes, and cookware u ...
, again standing for ''RDF Site Summary''. RSS 1.0 is an RDF format like RSS 0.90, but not fully compatible with it, since 1.0 is based on the final RDF 1.0 Recommendation. *RSS 1.1 is also an open format and is intended to update and replace RSS 1.0. The specification is an independent draft not supported or endorsed in any way by the RSS-Dev Working Group or any other organization. The RSS 2.* branch (initially UserLand, now Harvard) includes the following versions: *RSS 0.91 is the simplified RSS version released by Netscape, and also the version number of the simplified version originally championed by
Dave Winer Dave Winer (born May 2, 1955 in Queens Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. It is the largest borough of New York City New York City (NYC), often simply called New York, ...
from Userland Software. The Netscape version was now called ''Rich Site Summary''; this was no longer an RDF format, but was relatively easy to use. *RSS 0.92 through 0.94 are expansions of the RSS 0.91 format, which are mostly compatible with each other and with Winer's version of RSS 0.91, but are not compatible with RSS 0.90. *RSS 2.0.1 has the internal version number 2.0. RSS 2.0.1 was proclaimed to be "frozen", but still updated shortly after release without changing the version number. RSS now stood for ''Really Simple Syndication''. The major change in this version is an explicit extension mechanism using XML namespaces. Later versions in each branch are backward-compatible with earlier versions (aside from non-conformant RDF syntax in 0.90), and both versions include properly documented extension mechanisms using XML Namespaces, either directly (in the 2.* branch) or through RDF (in the 1.* branch). Most syndication software supports both branches
"The Myth of RSS Compatibility"
an article written in 2004 by RSS critic and
Atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of ato ...
advocate , discusses RSS version compatibility issues in more detail. The extension mechanisms make it possible for each branch to copy innovations in the other. For example, the RSS 2.* branch was the first to support
enclosures Enclosure or Inclosure is a term, used in English landownership, that refers to the appropriation of "waste" or "common land Common land is land owned by a person or collectively by a number of persons, over which other persons have certa ...
, making it the current leading choice for podcasting, and is the format supported for that use by
iTunes iTunes () is a media player, media library, Internet radio Internet radio (also web radio, net radio, streaming radio, e-radio, IP radio, online radio) is a digital audio Digital audio is a representation of sound recorded in, or ...

iTunes
and other podcasting software; however, an enclosure extension is now available for the RSS 1.* branch
mod_enclosure
Likewise, the RSS 2.* core specification does not support providing full-text in addition to a synopsis, but the RSS 1.* markup can be (and often is) used as an extension. There are also several common outside extension packages available, e.g. one from
Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation which produces Software, computer software, consumer electronics, personal computers, and related services. Its best-know ...

Microsoft
for use in
Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, (from August 16, 1995 to March 30, 2021) commonly abbreviated IE or MSIE) is a discontinued series of graphical user interface, graphical web browsers develo ...
7. The most serious compatibility problem is with HTML markup. Userland's RSS reader—generally considered as the reference implementation—did not originally filter out
HTML The HyperText Markup Language, or HTML is the standard markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntacticall ...

HTML
markup from feeds. As a result, publishers began placing HTML markup into the titles and descriptions of items in their RSS feeds. This behavior has become expected of readers, to the point of becoming a
de facto ''De facto'' ( ; , "in fact") describes practices that exist in reality, even though they are not officially recognized by laws. It is commonly used to refer to what happens in practice, in contrast with ''de jure'' ("by law"), which refers to th ...
standard. Though there is still some inconsistency in how software handles this markup, particularly in titles. The RSS 2.0 specification was later updated to include examples of entity-encoded HTML; however, all prior plain text usages remain valid. , tracking data from www.syndic8.com indicates that the three main versions of RSS in current use are 0.91, 1.0, and 2.0, constituting 13%, 17%, and 67% of worldwide RSS usage, respectively. These figures, however, do not include usage of the rival web feed format Atom. , the syndic8.com website is indexing 546,069 total feeds, of which 86,496 (16%) were some dialect of Atom and 438,102 were some dialect of RSS.


Modules

The primary objective of all RSS modules is to extend the basic
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
schema established for more robust syndication of content. This inherently allows for more diverse, yet standardized, transactions without modifying the core RSS specification. To accomplish this extension, a tightly controlled vocabulary (in the RSS world, "module"; in the XML world, "schema") is declared through an
XML namespace#REDIRECT XML namespace XML namespaces are used for providing uniquely named Data element, elements and attributes in an XML document. They are defined in a W3C recommendation. An XML instance may contain element or attribute names from more than one ...
to give names to concepts and relationships between those concepts. Some RSS 2.0 modules with established namespaces are: *
Media RSS Media RSS (MRSS) is an RSS extension that adds several enhancements to RSS enclosures, and is used for syndicating multimedia Multimedia is a form of communication that combines different content forms such as text, audio, images, animations ...
(MRSS) 2.0 Module
OpenSearch RSS 2.0 Module


Interoperability

Although the number of items in an RSS channel is theoretically unlimited, some
news aggregators In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and softwa ...
do not support RSS files larger than 150KB. For example, applications that rely on the Common Feed List of
Windows Microsoft Windows, commonly referred to as Windows, is a group of several proprietary {{Short pages monitor
RSS 0.90 Specification

RSS 0.91 Specification

RSS 1.0 Specifications

RSS 2.0 Specification

History of the RSS Fork
(Mark Pilgrim)

Tutorial with example {{DEFAULTSORT:Rss Computer file formats Computer-related introductions in 1999 Open formats Web syndication formats
XML-based standards This category exists to combine the sometimes bewildering array of abbreviations associated with XML technology, not all of which are endorsed by the same organisations. XML Computer standards Communications protocols {{CatAutoTOC ...