SharePoint 2013-"The blob cache is not enabled in this web application. Image renditions will not be generated until the blob cache is enabled. For information on turning on the blob cache, please review the product documentation."

Image Rendition is new feature in SharePoint 2013, those users can re size the images to a fix predefined position to use them in web parts or pages. So that it can help us to improve the user experience of site by changing the image sizes. Using Image renditions we can save the image in different number of scaled variations. Dynamic rendering of the image will effect on the performance of the site. We can fix this by using image rendition.

We have to enable BLOB cache for image rendition. We can check Image rendition in Site Settings -> Image rendition in “Look and Feel” group.

 An Error message will be shown on the top of the page saying that “The blob cache is not enabled in this web application. Image renditions will not be generated until the blob cache is enabled. For information on turning on the blob cache, please review the product documentation”, if we are not enabled the blob cache.

Blob cache is a disk based caching feature. It will eliminate the database round trips in SharePoint. It will load the data from DB and saves on the web client and serves from cache. Generally Blob cache objects are images, Audio or Video files.

To enable Blob cache, Go to IISManger (Run -> inetmgr)

Go to site that need to enable Blob cache. Explore the site, find the web.config file.

Search for “BlobCache”, go to end of the line and make “enabled” value from “false” to “true” 

To use image rendition, publishing feature must be activated in the site.