Atom is an XML -based file format used to syndicate content. Atom was designed to be a universal publishing standard for blogs and other Web sites where content is updated frequently. Users visiting a Web site with an Atom feed can discover a file described as "atom.xml" in the URL that can be copied and pasted into an aggregator to subscribe to the feed.
Atom was originally developed as an alternative to RSS 2.0, the standard developed by Dave Winer and copyrighted by Harvard University, as a means of improving perceived shortcomings of the RSS format by the blogging community.
Atom is differentiated from RSS in several ways:
- Atom was developed to be vendor neutral and freely extensible by any user; it is an "open standard."
- Atom lies within an XML-namespace.
- Atom includes "autodiscovery," allowing feed aggregators to automatically detect the presence of a feed.
- Atom differentiates between relative and non-relative URIs.
- Atom has separate "summary" and "content" elements.
- Atom explicitly labels a payload as plaintext or HTML .
- Each entry has a globally unique ID.
The current standard, 1.0, was submitted to the IETF to be an official protocol standard in late 2005 under than name "Atom Syndication Format." Atom has been adopted by many syndication tools, including Google's Blogger, Gmail and Google News. Microsoft has added Atom support to the feed browser integrated into Internet Explorer 7.