Web feed

A web feed is a machine-readable XML document (commonly RSS or Atom) that delivers a sequence of content items for syndication, subscription, aggregation, and automated exchange between services.

Overview

A web feed is a structured, typically XML-based document that publishes a sequence of discrete content items from a regularly updated source such as a blog, news site, podcast, or other service. Feeds allow consumers to receive updates without revisiting a website, enabling both human-oriented applications (feed readers, news apps) and machine-to-machine exchange (automated processing, notifications and workflows). When a site makes a feed available this is often called syndication; when a tool combines content from many feeds for a single display this is called aggregation.

Structure and common elements

Although formats and vocabularies vary, typical web feeds include metadata about the source and a repeating set of items or entries. Common elements found in many feeds include channel or feed metadata (a title, a link to the originating site and a description), and individual items or entries each with a title, link, summary or full content, timestamps such as publication or update dates, and often a persistent identifier. Items may carry enclosures or attachments for media, which is the mechanism widely used for distributing podcast episodes.

Formats and standardization

The most widely used feed formats are RSS and Atom; there is also an RDF-based approach used by some implementations. RSS grew out of early web publishing practices and exists in several variant version lines. Atom was developed later with a more strictly defined specification to address limitations perceived in earlier formats. Each format defines element names, expected content types and rules for representation; readers and libraries parse these formats to present entries to users or to ingest them for processing by other systems.

Discovery and delivery

Feeds can be discovered in web pages using link elements placed in HTML headers, via explicit URLs advertised on a site, or through feed directories and search. The basic delivery model is polling, where a client periodically requests the feed and checks for new items. To reduce latency and server load, several extensions and protocols add push-like behavior or notify subscribers when updates are available. HTTP features such as caching headers and conditional requests are commonly used to make polling more efficient.

Uses and applications

Web feeds are used for a variety of purposes: aggregating headlines in news readers, delivering podcast episodes via enclosures, driving content into dashboards or social displays, enabling corporate notifications and data exchange, and triggering automation in workflows. End users typically subscribe through feed reader applications or services embedded in email clients and browsers, while organizations may ingest feeds directly into content management systems, analytics pipelines or notification systems.

Interoperability and tooling

Many programming languages and platforms provide libraries to parse and generate feed formats, and validators exist to check conformance to common specifications. Because implementations differ, practical interoperability often relies on tolerant parsers that accept minor variations. Discoverability practices, well-known URL patterns and link elements in HTML help tools find and use feeds automatically.

Privacy, security and content considerations

Feeds are inherently machine-readable and often public; publishers should consider privacy and access control before exposing sensitive data. Feeds can be served over encrypted transport to protect content in transit, and publishers may require authentication for private feeds. Consumers should be cautious about executing embedded content without validation, since feeds can include links and markup that lead to external resources.

Comparison with APIs and other technologies

Feeds provide a push-friendly, standardized stream of content suitable for many subscription scenarios, whereas web APIs typically offer on-demand queries and richer interaction models (filtering, pagination, complex queries). Feeds remain valuable where a simple, incremental stream of updates is needed, when backward compatibility and low integration cost are priorities, or when widespread support from existing clients is required.

Best practices

Provide clear feed metadata (title, link, description) so aggregators can identify the source.
Include persistent identifiers for items to help clients detect duplicates and updates.
Use timestamps for publication and update times to support efficient synchronization.
Use HTTP caching and conditional requests to reduce unnecessary bandwidth use.
Protect private feeds with appropriate authentication and serve feeds over secure transport when needed.