Realtime streams deliver three different events that occur in the Wikimedia dataset. Page deletions, updates, and visibility changes. Page deletions occur when a page from a supported Wikimedia project is deleted, and thus should be removed from a mirrored dataset. Page updates occur when there is any change to content and name (title) as well as any page creation. Page visibility changes occur when a volunteer hides a part of a page which can be a good signal of potentially harmful content. Those parts can include content, comments or users and are related to a specific revision of a page.