There are two major types of XML APIs: tree-based APIs; and event-based APIs. A tree-based API parses an XML document into an internal tree structure, allowing an application to navigate that tree. An event-based API reports parsing events (such as the start and end of elements) directly to the application through callbacks, and does not usually build an internal tree. The application implements handlers to deal with the different events, much like handling events in a graphical user interface.

SAX, the Simple API for XML, is a standard interface for event-based XML parsing. DOM parsers utilize tree-based XML parsing.