The NPSavedData object contains a block of per-instance information that Communicator saves after the instance is deleted. This information can be returned to another instance of the same plug-in if the user returns to the web page that contains it.
You can use the plug-in's NPP_Destroy function to allocate an NPSavedData object using the NPN_MemAlloc function, fill in the fields, and return it to the browser as an output parameter. See "Instance Destruction" for a code example that shows how to use NPSavedData.
If the user revisits a web page that contains a plug-in, the browser returns the NPSavedData to the new instance of the plug-in in a call to NPP_New. After this, the plug-in is responsible for keeping or deleting the objects as necessary.