What is caching?
The content of a webpage can be copied and saved (or "cached") at a number of points between the server where it lives and the browser where it is viewed.
Why bother caching content?
This is desirable because it can greatly speed up the browsing experience. For example, the Williams wordmark in our official typeface is an image that is displayed on almost every page. Most browsers will cache the image and, when they see a new request for it, will display the image from the cache rather than requesting a new copy from the server. It is significantly faster to build the page with the cached image vs waiting for the new copy from the server.
What is the downside?
The main drawback is that a cached version of an image, file, or text may become out of sync with the "real" version (the version stored in the content management system). This is because software that caches content typically gives each item an expiration date and will use the cached version until it has "expired." Changes made to the content after it was cached and before it expires may not be seen by site visitors.
Where is the content cached?
There are two places where page content is typically cached.
- Your web browser.
- The content delivery network (CDN) used by the college to speed up its websites.
Below are two options for clearing the cached version of a webpage. Reloading the page in your browser attempts to clear the browser cache, and clicking the refresh button after editing a page clears the CDN cache.
I just edited a webpage, why can’t I see the changes?
Typically, you are not seeing the changes because your browser is displaying a cached version of the page. Reloading the webpage in your browser will cause it to retrieve the latest version of the content. Use the appropriate keyboard shortcut to do a “hard reload” that requests all the latest information.
- PC: ctrl-shift-r
- Mac: command-shift-r
The reload trick didn’t work, what next?
Logged-in site editors have the ability to clear the version of a page cached by our content delivery service. Just click the “Purge Page Cache” button in the black bar at the top of the page you want to refresh (see screenshot below). In general, this also happens automatically every 4 hours. This is sometimes necessary in cases where content from one page is included on another page. When a page is edited, its cached version is cleared automatically. The page that includes the edited content may not have been cleared from the cache. See overview for more detail.