On its own, Drupal produces a brand new copy of each webpage every time that page is viewed. Considering most of the time the content on a given page has not changed since the last time it was viewed, this behavior is inefficient. It is also very resource intensive.
To gain greater efficiency, UMN Drupal sites use caching. Caching is a technique that stores copies of webpages to give to viewers. When Drupal detects an update to a web page, it often will update the “cached” version of that page to give to the next viewer.
UMN Drupal sites have two kinds of caching, Drupal Cache and Varnish. Drupal Cache is the caching layer that users of a Drupal site interact with when logged in. Varnish is the caching layer that viewers of the website interact with when they visit the website.
These caching layers can have different behaviors based on how a site builder has configured the particular UMN Drupal site. If you are a contributor to your website and have questions on how caching works for you, please talk to your site’s administrator.
If you are a site administrator:
You can clear the Drupal cache for individual pages by navigating to: /admin/config/system/expire/manualpurge