RSS (Really Simple Syndication or Rich Site Summary) is a familiar name in the internet world, but Atom (Atom Syndication Format) may not ring a bell for many.

Content Syndication is a mechanism using which the contents of a website including articles, news, blogs and forums are published partially or fully to other websites in a specific format. RSS and Atom are the two main standards of web syndication.

Atom was developed to avoid the limitations and flaws of RSS. Though Atom is more robust than RSS, the latter still remains a widely used standard. Just as how Xerox has become synonymous to photocopying, RSS has generally become a common term to refer to all feeds including Atom.

Some websites provide feeds in both these formats, while the other in one of these formats. For examples, IBM developerWorks website has both Atom and RSS feeds, Google supports only Atom and CNN has only RSS.

Some differences between RSS and Atom are listed below.

Criteria RSS Atom
File extension .rss or .xml .atom or .xml
Media type identification application/rss+xml application/atom+xml
Extension to namespaces Not Supported Supported
Payload content support Plain text and escaped HTML Plain text, escaped HTML, XHTML, XML, Base64-encoded binary and references to external binary content
Content type identification Not available; cannot identify if the content is plain text or escaped HTML Explicit identification of content is supported
Date formats Feed creation or last updated date Website last updated date
Internationalization Language context at the feed level Language context at every individual element level
Modularity Vocabularies not usable in other XML vocabularies Vocabularies reusable outside the context of the feed
Robustness Easy Rigid
Ease of aggregation Complex Easy
Popularity trend Steady Increasing

Both the hosting website and the feeding website tend to gain from syndication. In simple terms, the hosting website gains exposure of its content across numerous websites and the sites consuming the feeds gains more depth in the information displayed in its pages.

Both RSS and Atom have their own respective backing in the industry and both these will likely to continue their sustenance. Selecting to implement either of the standards for a website is need and convenience based.