In computing, a feed aggregator, also known as a feed reader, news reader or simply aggregator, is client software or a Web application which aggregates syndicated web content such as news headlines, blogs, podcasts, and vlogs in a single location for easy viewing.
Aggregators reduce the time and effort needed to regularly check websites for updates, creating a unique information space or "personal newspaper." Once subscribed to a feed, an aggregator is able to check for new content at user-determined intervals and retrieve the update. The content is sometimes described as being " pulled" to the subscriber, as opposed to " pushed" with email or IM. Unlike recipients of some "pushed" information, the aggregator user can easily unsubscribe from a feed.
Aggregator features are frequently built into portal sites (such as My Yahoo! and iGoogle), modern Web browsers and email programs.
The aggregator provides a consolidated view of the content in a single browser display or desktop application. Such applications are also referred to as RSS readers, feed readers, feed aggregators, news readers or search aggregators. Aggregators with podcasting capabilities can automatically download media files, such as MP3 recordings. In some cases, these can be automatically loaded onto portable media players (like iPods) when they are connected to the PC.
Recently, so-called RSS-narrators have appeared, which not only aggregate text-only news feeds, but also convert them into audio recordings for offline listening.
The syndicated content an aggregator will retrieve and interpret is usually supplied in the form of RSS or other XML-formatted data, such as RDF/XML or Atom.
The variety of software applications and components that are available to collect, format, translate, and republish XML feeds is a testament to the flexibility of the format and has shown the usefulness of presentation-independent data.
The most commonly known web-based aggregators are reader applications on the web. These are meant for personal use and are hosted on remote servers. Examples include the popular Google Reader or Bloglines. Because the application is available via the Web, it can be accessed anywhere by a user with an Internet connection.
More advanced methods of aggregating feeds are provided via AJAX coding techniques and XML components known as Web widgets. Ranging from full-fledged applications to small fragments of code that can be integrated into larger programs, they allow users to aggregate OPML files, email services, documents, or feeds into a single interface. Many customizable homepage/portal implementations such as iGoogle, Live.com, My Yahoo!, and Pageflakes provide such functionality.
In addition to aggregator services mainly for individual use, there are web applications that can be used to aggregate several blogs into one. One such variety - called planet sites - are used by online communities to aggregate community blogs in a centralized location. They are named after the Planet aggregator, a server application designed for this purpose. There are also web-based services that anyone can use, to create one merged feed of several blogs.
Client software aggregators are installed applications designed to collect Web feed subscriptions and group them together using a user-friendly interface. The graphical user interface of such applications often closely resembles that of popular e-mail clients, using a three-panel composition in which subscriptions are grouped in a frame on the left, and individual entries are browsed, selected, and read in frames on the right.
Software aggregators can also take the form of news tickers which scroll feeds like ticker tape, alerters that display updates in windows as they are refreshed, web browser macro tools or as smaller components (sometimes called plugins or extensions), which can integrate feeds into the Operating System or software applications such as a Web browser.
Many programming languages have libraries that are able to download, process, generate and upload RSS feeds. Perl for example has several libraries in the XML::RSS name space of CPAN.
One of the problems with news aggregators is that the volume of articles can sometimes be overwhelming, especially when the user has many Web feed subscriptions. As a solution, many feed readers allow users to tag each feed with one or more keywords which can be used to sort and filter the available articles into easily navigable categories. Another option is to import the user's Attention Profile to filter items based on their relevance to the user's interests.