Providing notification of document repository events to external systems

Remote event receivers can register with a document repository computing system to receive notifications of events occurring at a document repository. The remote event receivers may register to receive notifications synchronously, whereby the remote event receivers can provide a response to the notification prior to the occurrence of the event, or asynchronously, whereby the remote event receivers provide no response. Synchronous remote event receivers can also specify in a response to the notification that the event should be canceled or may specify properties that should be changed. Remote event receivers can be pre-event receivers that receive notifications prior to the occurrence of an event, or post-event receivers that receive notifications following the event. When an event is to occur at the document repository, notifications are provided to the pre-event remote event receivers. Once the event has occurred, notifications are provided to the post-event remote event receivers.