Indexing Service

Last Edited



Indexing Service is a Windows operating system service that extracts content from files and constructs an indexed catalog to facilitate efficient and rapid searching.

Indexing Service
Indexing Service

How Indexing Service works

Indexing Service can extract both text and property information from files on the local host and on remote, networked hosts. The files can be simply members of a selected file system or part of a virtual Web hosted by, for example, Internet Information Services (IIS).

Indexing Service extracts the content by filtering, using filter components that understand a file’s format. The format could include multi-language features such as international languages and locales. A filter component implements the IFilter interface, which supplies methods to read a file to extract text and properties. Windows 2000 and Microsoft Windows XP supply filters for Microsoft Office files, Hypertext Markup Language (HTML) files, Multipurpose Internet Mail Extension (MIME) messages, and plain-text files.

Indexing Service then merges the extracted information into catalogs of indexes for efficient searches. Indexing is the overall process of filtering, creating index entries, and merging them into catalogs.

The final step in the indexing process is creation of a catalog that contains a master index (and any temporary word lists and shadow indexes) storing words and their locations within a set of indexed documents. Subsequently, searching, or querying, the catalogs for particular word combinations uses the master index as well as word lists and shadow indexes to execute queries quickly and efficiently.

Indexing Service is no longer available

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.

In Windows 7, it has been replaced by a newer Windows Search indexer.

History of Indexing Service

Indexing Service was a desktop search service included with Windows NT 4.0 Option Pack as well as Windows 2000 and later. The first incarnation of the indexing service was shipped in August 1996 as a content search system for Microsoft’s web server software, Internet Information Services (IIS). Its origins, however, date further back to Microsoft’s Cairo operating system project, with the component serving as the Content Indexer for the Object File System. Cairo was eventually shelved, but the content indexing capabilities would go on to be included as a standard component of later Windows desktop and server operating systems, starting with Windows 2000, which includes Indexing Service 3.0.

In Windows Vista, the content indexer was replaced with the Windows Search indexer which was enabled by default. Indexing Service is still included with Windows Server 2008 but is not installed or running by default.

Indexing Service has been deprecated in Windows 7 and Windows Server 2008 R2. It has been removed from Windows 8.