httpCompression Element [IIS Settings Schema]
Note
For more information about the httpCompression element, see the following topic on the Microsoft IIS.net Web site: HTTP Compression <httpCompression>.
Configures HTTP compression settings for a Web server.
Syntax
Attributes and Elements
The following sections describe attributes, child elements, and parent elements for this section.
Attributes
Attribute |
Description |
|---|---|
cacheControlHeader |
Optional string attribute. Specifies the directive that IIS adds to the Cache-Control header that overrides the HTTP Expires header. This attribute ensures that older clients and proxy servers do not attempt to cache compressed files. To enable this setting, you must set the sendCacheHeaders attribute to true. The WWW service must be restarted before changes to this property take effect. The default value is "max-age=86400". |
directory |
Optional string attribute. Specifies the directory where compressed versions of static files are temporarily stored and cached. The default value is "%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files". Note In IIS 6.0, the default directory path for IIS temporary compressed files was "%Windir%\IIS Temporary Compressed Files". |
doDiskSpaceLimiting |
Optional Boolean attribute. Specifies whether a limit exists for the amount of disk space that all compressed files, which are stored in the compression directory specified by the directory attribute, can occupy. The default value is true. |
dynamicCompressionDisableCpuUsage |
Optional integer attribute. Specifies the percentage of CPU utilization at which dynamic compression will be disabled. Note This attribute acts as an upper CPU limit at which dynamic compression is turned off. When CPU utilization falls below the value specified in the dynamicCompressionEnableCpuUsage attribute, dynamic compression will be reenabled. The default value is 90. |
dynamicCompressionEnableCpuUsage |
Optional integer attribute. Specifies the percentage of CPU utilization below which dynamic compression will be enabled. The value must be between 0 and 100. Average CPU utilization is calculated every 30 seconds. Note This attribute acts as a lower CPU limit below which dynamic compression is turned on. When CPU utilization rises above the value specified in the dynamicCompressionDisableCpuUsage attribute, dynamic compression will be disabled. The default value is 50. |
expiresHeader |
Optional string attribute. Specifies the content of the HTTP Expires header that is sent with all requested compressed files, together with the Cache-Control header specified in the cacheControlHeader attribute. This combination of headers ensures that older clients and proxy servers do not try to cache compressed files. To enable this setting, you must set the sendCacheHeaders attribute to true. The World Wide Web Publishing Service (WWW service) must be restarted before changes to this property take effect. The default value is "Wed, 01 Jan 1997 12:00:00 GMT". |
maxDiskSpaceUsage |
Optional integer attribute. Specifies the number of megabytes of disk space that compressed files can occupy in the compression directory. When the space used by compressed files exceeds 90 percent of the value in this attribute, IIS deletes the least recently used files until a 90-percent usage level is reached. Note In IIS 6.0, this limit is expressed in bytes; in IIS 7.0, it is expressed in megabytes. In IIS 7.0 the limit is applied per application pool. The default value is 100. |
minFileSizeForComp |
Optional integer attribute. Specifies the minimum number of kilobytes a file must contain in order to use on-demand compression. The default value is 256. |
noCompressionForHttp10 |
Optional Boolean attribute. Specifies whether compression is disabled for requests that contain an HTTP 1.0 version number. Note Some HTTP 1.0 clients do not handle the caching of compressed objects correctly. You can use this setting to avoid returning a compressed file to a client that cannot decompress it. The default value is true. |
noCompressionForProxies |
Optional Boolean attribute. Specifies whether the HTTP 1.1 response is disabled for compression requests that come through proxy servers. Note Some HTTP proxy servers do not handle the caching of compressed objects correctly. You can use this setting to avoid returning a compressed file to a proxy server that cannot decompress it. The default value is true. |
noCompressionForRange |
Optional Boolean attribute. Specifies whether compression is disabled for HTTP requests that include the Range header. Note Some clients cannot handle range requests correctly. You can use this setting to avoid returning a compressed file to a client that cannot decompress it. The default value is true. |
sendCacheHeaders |
Optional Boolean attribute. Specifies whether the headers configured in cacheControlHeader and expiresHeader are sent with each compressed response. The default value is false. |
staticCompressionDisableCpuUsage |
Optional integer attribute. Specifies the percentage of CPU utilization at which static compression is disabled. The value must be between 0 and 100. Average CPU utilization is calculated every 30 seconds. Note This property acts as an upper CPU limit at which static compression is turned off. When CPU utilization falls below the value specified in the staticCompressionEnableCpuUsage attribute, static compression will be reenabled. The default value is 100. |
staticCompressionEnableCpuUsage |
Optional integer attribute. Specifies the percentage of CPU utilization at which static compression is enabled. The value must be between 0 and 100. Average CPU utilization is calculated every 30 seconds. Note This property acts as a lower CPU limit below which static compression is turned on. When CPU utilization rises above the value specified in the staticCompressionDisableCpuUsage attribute, static compression will be disabled. The default value is 50. |
Child Elements
Element |
Description |
|---|---|
scheme |
Optional element. Specifies the compression scheme (Gzip or Deflate) IIS uses to compress client requests. |
dynamicTypes |
Optional element. Specifies configuration settings for dynamic compression. |
staticTypes |
Optional element. Specifies configuration settings for static compression. |
Parent Elements
Element |
Description |
|---|---|
configuration |
Specifies the root element in every configuration file that is used by IIS 7. |
system.webServer |
Specifies the top-level section group (in ApplicationHost.config) in which this element is defined. |
Remarks
For more information about the httpCompression element, see the following topic on the Microsoft IIS.net Web site: HTTP Compression <httpCompression>.
Element Information
Configuration locations |
Machine.config ApplicationHost.config Root application Web.config Application Web.config Directory Web.config |
Requirements |
Microsoft Internet Information Services (IIS) version 7.0 |
See Also
Reference
scheme Element for httpCompression [IIS Settings Schema]
staticTypes Element for httpCompression [IIS Settings Schema]
dynamicTypes Element for httpCompression [IIS Settings Schema]