To directly manipulate an object, both the source and the target must support the object type, which describes the format of the object. For example, the input to a C compiler could have the type Plain Text (DRT_TEXT). The hstrType field in the DRAGITEM data structure conveys this information for each object being dragged. The type is represented by a string handle. The target should check to see if it supports the type before allowing the user to drop the object.

Several DTYP_* constants are defined as notational conveniences for common types of data. An application can extend these types by defining its own character strings and then creating string handles for them using DrgAddStrHandle.