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Three Types of Web Caching that Cause Old Content to Appear on Your Website

When handling support requests at InetSolution, I often battle with caching systems that are designed to improve website speed and to mitigate the risks of distributed denial of service (DDoS) attacks, but cause delays in viewing the latest content or CSS changes on a website. The support requests I see most often usually originate from a content manager who recently visited her web page in her browser published a change to the text or graphic on a page, but still sees the old content in her browser after reloading the page.

Of course, when I receive the request and view the page, sometimes I see the new content, while other times I, too, still see the old content even though the new content apperas inside of the CMS (e.g., WordPress, Kentico, etc.).

When external visitors see website content that doesn't contain the most recent updates published from the CMS, it is usually the result of caching, either at the CMS level, the web server level, or the in the local hard disk cache of the web browser (e.g., Chrome, Firefox, etc.).

What is CMS caching?

When your CMS is serving an older, cached copy of your content.

caching example 1

We build and host websites on many platforms, including WordPress, Kentico, and other flavors of content management platforms. All of the CMSs we host use have built-in (or plug-in based) caching to speed up pages (Google loves fast pages!) and reduce bandwidth usage.

When a content manager makes a change to a page, sometimes the CMS caching mechanism will automatically clear the CMS cache and immediately start serving the updated content. Having said that, this behavior is not always reliable. Sometimes it is due to complex configuration settings within the CMS or plugin that do not function as users expect, so it is not uncommon for these cache clearing to misbehave or simply work differently than expected, which results in external website visitors still seeing the old, cached content until the next regularly scheduled cache refresh occurs. Sometimes these cache intervals can be several hours between each execution!

Unfortunately, the CMS cache is only one caching mechanism that can result in website visitors seeing out of date content.

What is web server (sometimes called server-side) caching?

When the server between the visitor's browser and the website are serving an older, cached copy of your content.

caching example 2

What many people do not realize is that nearly all modern, high-security websites actually have multiple layers or "servers" between the web browser and the web server. One of the most common components in a secure web hosting setup today is a caching proxy server, many of which are designed to help mitigate DDoS attacks or to simply improve the speed of the website, both for user experience and for SEO purposes. Nearly all of these proxy servers leveraging caching to serve a cached version of your website. The benefit to visitors is that web pages load much faster. The benefit to site owners is that these proxy servers provide protection to the website and often reduce website hosting costs substantially. Of course, the drawback is that sometimes they result in caching frustration for site content editors!

These caching proxy servers try to detect content updates and clear their caches automatically, but they sometimes will store certain data, such as images, JavaScript, CSS, and similar static data for predefined expiration periods, even when the source object has been recently updated. When this occurs, the proxy cache must be manually cleared for changes to become immediately available. Usually only system administrators have access to these types of proxy servers to perform manual cache clearing, so these often results in a support request to the web or security teams.

At InetSolution, whenever possible we build automated processes within our CMS deployments that clear this type of caching when content changes to minimize the time it takes to clear the proxy server caches, but not all CMS caching mechanisms support this kind of automated integration. Even with our automated processes, sometimes it can take up 15 to 30 minutes for the thousands of cache servers to fully clear their caches.

Local web browser caching

When your own web browser loads a cached copy of your content.

caching example 3

Pages, JavaScript, cascading style sheets (CSS), images, PDFs, and other documents are all normally cached on your devices hard drive by your web browser. Your browser will try and load as little as possible from the server to make surfing the web seem faster. If it notices you have a file in your browser cache with the same name and size as the file on the web server, it will skip requesting a fresh copy from the web server and load the one it has locally. This can cause visual changes (CSS and images), functionality (JavaScript), and even documents to appear as if they haven’t been updated.

There are a few methods to help clear your local browser cache.

  1. You may try opening a new Incognito or Private window for your browser and loading the site there. This isn’t always foolproof however and cached content has still appeared in our experience.
  2. You can turn on Developer Tools in your browser which can give you some control over disabling caching entirely. This is usually too advanced for some of our clients or potentially your customers or members.
  3. Holding shift and clicking the refresh button (several times) seems to be a silver bullet that most people can figure out – and it works the vast majority of the time!

Hopefully these descriptions give you a better understanding of caching to help you identify where the issue lies, to better initiate support, and get your website displaying as intended quickly.

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