The URL Subscription Architecture (URLSA) is an open system for subscribing to frequently updated digital content on the web, such as blogs, news stories, and private conversations. It was designed as an alternative to RSS that supports social subscribing, private subscriptions, and rich content. The URL Subscription Architecture (URLSA) is an open system for subscribing to frequently updated digital content on the web, such as blogs, news stories, and private conversations. It was designed as an alternative to RSS that supports social subscribing, private subscriptions, and rich content. URLSA users can subscribe themselves and other users to the URL of some content and, once subscribed, are notified when the content at that URL is updated. Users typically maintain a list of subscriptions to everything from news stories to conversations. The architecture allows users to generate private content, such as a conversation or a photo album, on the fly and subscribe other users to it. The fact that URLSA is a content-less architecture, that users subscribe to the URL of the content rather than the content itself, means that virtually any type of content that is addressable by a URL can be made subscribable.