Introduction to BLOB Caching in SharePoint

The BLOB cache in SharePoint stores copies of  binary large object files that are used by webpages, such as images and CSS files, on the file system of WFE servers. This enables SharePoint to serve these files more quickly because the WFE server no longer needs to retrieve the file from the database. Some SharePoint publishing features, such as image renditions, rely on the BLOB cache being enabled. It is disabled by default.

Enabling the SharePoint BLOB cache

Perform the following steps to enable the SharePoint BLOB cache:
  1. On a WFE server, open the Web.config file that corresponds to your SharePoint web application.
  2.  Locate the BlobCache element.


  1. <BlobCache location="C:\BlobCache\14" path="\. gif|jpg|jpeg|jpe|jfif|bmp|dib|tif|tiff|ico|png|wdp|hdp|css|js|asf|avi|flv|m4  
  2. v|mov|mp3|mp4|mpeg|mpg|rm|rmvb|wma|wmv)$" maxSize="10" enabled="false" />  
  1. Change the value of the enabled attribute to true.
  2. Adjust any other attributes as required, and then save and close the file. The BlobCache element can include the following attributes:

Location. Specifies where the cached files should be stored on the WFE server. By default, the BLOB cache creates a folder at C:\BlobCache\14.

  • Path. Specifies a regular expression that determines which file types are cached. By default, this includes all common media files types. You can add or remove file types as required.
  •  MaxSize. Specifies how large the BLOB cache is allowed to grow, in GB.
  •  Enabled. Specifies whether the BLOB cache is enabled.
You can also specify a max-age attribute. This specifies how long clients should cache files from the BLOB cache in their local browser caches, in seconds. If you do not specify a max-age value, SharePoint uses a default value of 86,400 seconds (24 hours). The max-age attribute does not affect how long items are stored in the BLOB cache; SharePoint automatically ensures that the BLOB cache contains the latest version of files from the content database.
When it ideal to  use the SharePoint BLOB cache

In most web applications, enabling the SharePoint BLOB cache will improve the performance of your sites and reduce the load on your database servers. BLOB cache settings can become problematic during site design—if designers are regularly editing images or CSS files, you may want to disable caching at least temporarily. The BLOB cache will increase disk I/O on your WFE servers, but this is not usually a bottleneck.