IIS 8.5 is the version of IIS that ships with Windows Server 2012 R2, and Windows 8.1.
IIS 8.5 includes several new features not found in IIS 8.0 or lower:
- Enhanced logging. An administrator can enable the logging of additional custom fields from request or response headers, or from server variables.
- Logging to event tracing for Windows. An administrator can enable the sending of logging information to Event Tracing for Windows (ETW).
- Dynamic Website activation. If there are a large number of configured sites (100 or greater, by default), the service will not activate any of the sites when the service is started.
- Idle Worker Process Page-Out. An administrator can enable an idle worker process to be suspended rather than terminated.