Filter DLLs

Note  Indexing Service is no longer supported as of Windows XP and is unavailable for use as of Windows 8. Instead, use Windows Search for client side search and Microsoft Search Server Express for server side search.

Filter DLLs allow a client to extract text information from the persistent representation of the contents and properties of a file. The Indexing Service filtering process CiDaemon.exe binds to the persistent handler for the IFilter interface implementation for the COM class of a file or for its registered file name extension. For details about how this occurs, see Persistent Handlers.

Every time it starts, Indexing Service registers DLLs, including persistent handlers, if they are listed in the registry key HKLM\system\currentcontrolset\control\contentindex\DllsToRegister.

To remove a filter DLL, delete the PersistentHandler registry entry associated with a document type and the filter DLL registry entry. (See Finding the Filter DLL for a File for more information). Once you have found the correct PersistentHandler entry, you can unregister it with the following syntax:

Regsvr32.exe /u filter.dll

This section contains topics that describe how to use the filter DLLs: