Page caching is a Rails mechanism which allows the request for a generated page to be fulfilled by the webserver (i.e. Apache or nginx), without ever having to go through the Rails stack at all. Obviously, this is super-fast. Unfortunately, it can't be applied to every situation (such as pages that need authentication) and since the webserver is literally just serving a file from the filesystem, cache expiration is an issue that needs to be dealt with.

INFO: Page Caching has been removed from Rails 4. See the[actionpack-page_caching gem](https://github.com/rails/actionpack-page_caching)

INFO: Page Caching has been removed from Rails 4. See the[actionpack-page_caching gem](https://github.com/rails/actionpack-page_caching). See[DHH's key-based cache expiration overview](http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works) for the newly-preferred method.

Page Caching cannot be used for actions that have before filters - for example, pages that require authentication. This is where Action Caching comes in. Action Caching works like Page Caching except the incoming web request hits the Rails stack so that before filters can be run on it before the cache is served. This allows authentication and other restrictions to be run while still serving the result of the output from a cached copy.

INFO: Action Caching has been removed from Rails 4. See the[actionpack-action_caching gem](https://github.com/rails/actionpack-action_caching)

INFO: Action Caching has been removed from Rails 4. See the[actionpack-action_caching gem](https://github.com/rails/actionpack-action_caching). See[DHH's key-based cache expiration overview](http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works) for the newly-preferred method.