An aggregator or news aggregator or feed reader is a client software that uses web feed to retrieve syndicated web content such as blogs, podcasts, vlogs, and mainstream mass media websites, or in the case of a search aggregator, a customized set of search results. 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 being built into portal sites such as My Yahoo! and Google; modern web browsers; and e-mail 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. 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.