The Atom Syndication Format is an XML-based standard for web content syndication, defined in IETF RFC 4287 (December 2005). Developed as a more precise and extensible alternative to RSS, Atom addressed longstanding interoperability problems in the web feed ecosystem by providing a clear, unambiguous specification with a formal data model. It remains widely supported across feed readers, content management systems, and web platforms.
Background
By the early 2000s, web syndication had become essential for blogs, news sites, and content aggregators, but the RSS format landscape was fragmented. Multiple incompatible versions of RSS existed (0.90, 0.91, 1.0, 2.0), with differing data models and ambiguous specifications. The Atom effort began in 2003 as a community project led by Sam Ruby, Mark Nottingham, and others who sought to create a single, well-defined syndication format. Work moved into the IETF Atompub Working Group, and RFC 4287 was published as a Proposed Standard in December 2005.
Purpose & Scope
Atom defines how to structure a feed document containing a collection of entries. Each feed has metadata (title, author, updated timestamp, unique identifier) and contains zero or more entries, each with its own metadata and content. The format is designed for any type of periodically updated content: blog posts, news articles, wiki changes, software changelogs, or podcast episodes.
A companion specification, the Atom Publishing Protocol (AtomPub, RFC 5023), extends Atom into a full read-write protocol for creating, editing, and deleting web resources over HTTP. AtomPub influenced the design of later RESTful API patterns and was adopted by platforms including Google's GData APIs.
Key Elements
| Element | Description |
|---|---|
| feed | Root element containing feed-level metadata and entries |
| entry | An individual item in the feed |
| title | Human-readable title for a feed or entry |
| link | URI associated with a feed or entry, with a rel attribute |
| updated | Timestamp of the most recent significant modification |
| id | Permanent, universally unique identifier (IRI) |
| author | Person or entity responsible for the content |
| content | The full or partial content of the entry |
| summary | Short summary or excerpt of the entry |
| category | Categorization of the feed or entry |
Serializations & Technical Formats
Atom documents are XML with the namespace http://www.w3.org/2005/Atom and the media type application/atom+xml. The format requires well-formed XML, which eliminates the parsing ambiguities that plagued RSS. Atom supports both inline content and linked content via the src attribute on the content element. Content can be plain text, HTML, XHTML, or arbitrary media types.
Governance & Maintenance
The specification was developed within the IETF Atompub Working Group, which concluded its work after publishing RFC 4287 (Atom format) and RFC 5023 (AtomPub). As an IETF RFC with Proposed Standard status, Atom is a stable specification that does not undergo regular revision cycles. Any updates would follow standard IETF processes. The format is registered with IANA under the application/atom+xml media type.
Notable Implementations
Atom feeds are supported by virtually all major feed readers and aggregators. Google adopted Atom extensively through its GData API framework, using AtomPub as the basis for Google Calendar, Blogger, and YouTube APIs (though these have since migrated to other formats). WordPress, Drupal, and most content management systems can generate Atom feeds alongside RSS. The format is also used in the Open Archives Initiative Object Reuse and Exchange (OAI-ORE) standard for describing aggregations of web resources.
Related Standards
- RSS — The earlier family of syndication formats that Atom was designed to improve upon