W3C Centralized Logging

Applies To: Windows Server 2003, Windows Server 2003 with SP1

W3C centralized logging is a global configuration on the server where all Web sites write data to a single log file. Data is stored in the log file using the W3C Extended log file format. The log file can be viewed in a text editor, unlike IIS Centralized Binary Logging which writes data in binary format and requires a parsing tool to view the data. W3C centralized logging is available in Windows Server 2003 Service Pack 1 or later.


FTP, NNTP, and SMTP do not support W3C centralized logging.

By default, IIS Web sites write data to individual log files (one log file per Web site). On servers hosting large numbers of sites (hundreds or thousands), the process of maintaining large numbers of open file handles to log files can negatively impact how the server scales. W3C centralized logging improves server scalability on servers hosting large numbers of sites because IIS requires only one open file handle for logging.

W3C centralized logging is a server property, not a site property, so when you enable this feature all Web sites on that server are configured to write log data to the central log file.


W3C centralized logging uses the W3C Extended log format, which includes the following four fields: HostHeader, Cookie, UserAgent, and Referrer. These fields are not available with centralized binary logging.

For the procedure to enable W3C centralized logging, see Enabling W3C Centralized Logging.

See Also


CentralW3CLoggingEnabled Metabase Property