RSS is a family of web feed formats used to publish frequently updated digital content, such as blogs, news feeds or podcasts.

Users of RSS content use programs called feed 'readers' or 'aggregators': the user 'subscribes' to a feed by supplying to their reader a link to the feed; the reader can then check the user's subscribed feeds to see if any of those feeds have new content since the last time it checked, and if so, retrieve that content and present it to the user.

The initials "RSS" are variously used to refer to the following standards:

• Really Simple Syndication (RSS 2.0)
• Rich Site Summary (RSS 0.91, RSS 1.0)
• RDF Site Summary (RSS 0.9 and 1.0)

RSS formats are specified in XML (a generic specification for data formats). RSS delivers its information as an XML file called an "RSS feed", "webfeed", "RSS stream", or "RSS channel".

Usage

Programs known as feed readers or aggregators can check a list of feeds on behalf of a user and display any updated articles that they find. It is common to find web feeds on major websites and many smaller ones. Some websites let people choose between RSS or Atom formatted web feeds; others offer only RSS or only Atom.

RSS-aware programs are available for various operating systems. Client-side readers and aggregators are typically constructed as standalone programs or extensions to existing programs such as web browsers and Email readers. Many browsers have integrated support for RSS feeds. There also are other applications that can convert an RSS feed into several usenet articles, viewable through the major newsreader software such as Mozilla Thunderbird or Forté Agent: an example of such applications are nntp//rss, a Java coded program, or RSS Feed Converter a script for the popular mail-newsserver Hamster.

Web-based feed readers and news aggregators such as YourLiveWire or NewsGator Online require no software installation and make the user's "feeds" available on any computer with Web access. Some aggregators combine existing web feeds into new feeds, e.g., taking all football related items from several sports feeds and providing a new football feed. There are also search engines for content published via web feeds like Feedster or Blogdigger.

On Web pages, web feeds (RSS or Atom) are typically linked with the word "Subscribe", an orange rectangle, a feed icon, or with the letters XML or RSS. Many news aggregators such as My Yahoo! publish subscription buttons for use on Web pages to simplify the process of adding news feeds.

History

Before RSS, several similar formats already existed for syndication, but none achieved widespread popularity or are still in common use today, as most were envisioned to work only with a single service. These originated from push and pull technologies. Two of the earliest examples are Backweb and Pointcast.

Between 1995 and 1997, Ramanathan V. Guha at Apple Computer's Advanced Technology Group developed the Meta Content Framework (MCF). MCF was a specification for structuring metadata information about web sites and other data, and the basis of Project X (aka Hot Sauce), a 3D flythrough visualizer for the web. When the research project was discontinued, Guha left Apple for Netscape, where he adapted MCF to use XML and created the first version of the Resource Description Framework (RDF).

In 1997 Microsoft created Channel Definition Format for the Active Channel feature of Internet Explorer 4.0, which never became popular. This was probably due to CDF being focused on commercial application of the concept and the extensive resources it required at a time when people were mostly on dial-up. Backweb and Pointcast were geared towards news, much like a personal API feed. Backweb later morphed into providing software updates, a precursor to the push update features by various companies now.

Dave Winer also designed his own XML syndication format for use on his Scripting News weblog, which was also introduced in 1997.

RDF Site Summary, the first version of RSS, was created by Dan Libby of Netscape in March 1999 for use on the My Netscape portal. This version became known as RSS 0.9. In July 1999, responding to comments and suggestions, Libby produced a prototype tentatively named RSS 0.91 (RSS standing for Rich Site Summary), that simplified the format and incorporated parts of Winer's scripting news format. This they considered an interim measure, with Libby suggesting an RSS 1.0-like format through the so-called Futures Document.

Soon afterwards, Netscape lost interest in RSS/XML, leaving the format without an owner, just as it was becoming widely used. A working group and mailing list, RSS-DEV, was set up by various users and XML notables to continue its development. At the same time, Winer unilaterally posted a modified version of the RSS 0.91 specification to the Userland website, since it was already in use in their products. He claimed the RSS 0.91 specification was the property of his company, UserLand Software. Since neither side had any official claim on the name or the format, arguments raged whenever either side claimed RSS as its own, creating what became known as the RSS fork.

The RSS-DEV group went on to produce RSS 1.0 in December 2000. Like RSS 0.9 (but not 0.91) this was based on the RDF specifications, but was more modular, with many of the terms coming from standard metadata vocabularies such as Dublin Core.

Nineteen days later, Winer released by himself RSS 0.92, a minor and supposedly compatible set of changes to RSS 0.91 based on the same proposal. In April 2001, he published a draft of RSS 0.93 which was almost identical to 0.92. A draft RSS 0.94 surfaced in August, reverting the changes made in 0.93, and adding a type attribute to the description element.

In September 2002, Winer released a final successor to RSS 0.92, known as RSS 2.0 and emphasizing "Really Simple Syndication" as the meaning of the three-letter abbreviation. The RSS 2.0 spec removed the type attribute added in RSS 0.94 and allowed people to add extension elements using XML namespaces. Several versions of RSS 2.0 were released, but the version number of the document model was not changed.

In November 2002, The New York Times began offering its readers the ability to subscribe to RSS news feeds related to various topics. In January, 2003, Winer called the New York Times' adoption of RSS the "tipping point" in driving the RSS format's becoming a de facto standard.

In July 2003, Winer and Userland Software assigned ownership of the RSS 2.0 specification to his then workplace, Harvard's Berkman Center for the Internet & Society.

In January 2005, Sean B. Palmer, Christopher Schmidt, and Cody Woodard produced a preliminary draft of RSS 1.1. It was intended as a bugfix for 1.0, removing little-used features, simplifying the syntax and improving the specification based on the more recent RDF specifications. As of July 2005, RSS 1.1 had amounted to little more than an academic exercise.

In April 2005, Apple Computer released Safari 2.0 with RSS Feed capabilities built in. Safari delivered the ability to read RSS feeds, and bookmark them, with built-in search features. Safari's RSS button is a blue rounded rectangle with RSS written inside in white, Safari's RSS icon/button. The favicon displayed defaults to a newspaper icon Safari's feed favicon..

In November 2005, Microsoft proposed its Simple Sharing Extensions to RSS.

In December 2005, the Microsoft IE team and Outlook team announced in their blogs that they will be adopting the feed icon first used in the Mozilla Firefox browser , effectively making the orange square with white radio waves the industry standard for both RSS and related formats such as Atom. Also in February 2006, Opera Software announced they too would add the orange square in their Opera 9 release.

In January 2006, Rogers Cadenhead relaunched the RSS Advisory Board in order to move the RSS format forward.