The Windows Search (WSearch) service supports the Instant Search feature, and it provides content indexing and property caching for file, email, and other content (by means of extensibility APIs). If the service is stopped or disabled, Windows Explorer cannot display virtual folder views of items, and Windows Explorer reverts to an item-by-item search.
The content that is indexed is based on the file and data types that are supported through add-ins included in the Windows Search service and the default inclusion and exclusion rules for folders in the file system. For example, the filters that are included in the Windows Search service support more than 200 common types of data, including support for Microsoft Office documents, Office Outlook email (in conjunction with the MAPI protocol handler), plaintext files, and HTML.
The main component of Windows Search is the indexer process, which is implemented as a Windows service running in the Local System account. The process is always running for all users even if no user is logged on. This enables the Windows Search service to maintain one index that is shared among all users, with security restrictions on content access, and to process remote queries from client computers on the network.
The Windows Search service includes a number of features to ensure that it protects the user experience and system performance when indexing. The following conditions cause the service to slow or pause indexing:
- High CPU usage by processes that are not search related
- High system I/O rate including file reads and writes, pagefile and file cache I/O, and mapped file I/O
- Low memory availability
- Low battery life
- Low disk space on the drive that is storing the index
The Windows Search service is installed by default, and its startup type is Automatic. When started in the default configuration, it logs on by using the Local System account.
The Windows Search service is dependent on the following system components:
- Remote Procedure Call (RPC)
- DCOM Server Process Launcher
- RPC Endpoint Mapper