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By using a high-performance CDN (Content Delivery Network), Webcentral brings your website the Edge, where it’s closest to your website’s visitors. This is done by caching static assets (HTML, JavaScript, CSS, and images) in the CDN’s cache until that cache expires or when your WordPress site tells the CDN to purge the cache. This FAQ explains how the CDN caching works and how to determine if any trouble that your site is experiencing may be related to the CDN or not. What can and cannot be cached? First, let’s define what a static asset is. A static asset is an element of your WordPress site that everyone who visits your site sees: HTML, CSS, and JavaScript. Static assets are the same for every visitor, so they can be cached. Dynamic content that changes for each user cannot be cached. Does the CDN cache modify my content? No. The CDN will never modify your content. If you are seeing issues with HTML, CSS, or JavaScript not working properly, and you’ve cleared the caches, you can be sure that this is not a CDN issue but instead may be an issue with a caching plugin. What is cached and where? The CDN has over 280 POPs (Points of Presence) around the globe. This network of POPs each has its own cache. Each location can share its cache with other locations for added speed. But, if the requested data is not cached at all, then it is retrieved from the origin: our servers. The only cached assets are:
  • HTML
  • CSS
  • JavaScript
  • Image files

How does the CDN know when to purge its cache? Whenever WordPress issues a cache flush, the CDN cache mu-plugin (Must-Use plugin) that we install on your site issues an API call to the CDN to clear the cache of all pages. You can also clear the cache manually. For information about how to do this, go to Manually purging the CDN cache on Webcentral Managed WordPress. Are images modified by the CDN? Unless an image is optimized by Cloudflare Polish, it’s unmodified. And, even if an image is converted to the WebP format, this is only reflected in the HTTP headers. The file name and the HTML that loads it are still unmodified. For more information about Cloudflare Polish and image optimization, go to Do I need to use an image optimization plugin or CDN on Webcentral Managed WordPress? Common non-CDN issues
  • Pages not updating.
  • CSS not updating.
  • Blank page for some pages.

These types of issues are not related to the CDN cache, even if purging the CDN cache fixes it for a while. It is usually caused by a invalid cache from caching plugins such as WP-Rocket. These can be also caused by theme optimization settings. In some cases, a caching plugin will not properly purge its cache. To test this, rename the wp-content/cache folder to wp-content/cache1 or some other name, and then clear the cache in your caching plugin one more time. You should see a new cache folder, and you can then remove the renamed cache folder, and the content should show correctly. If not, try an incognito/private browser window, another browser, or even a different device to test. Do you have more questions about caching? If you have any other questions, please do not hesitate to open a support ticket at https://theconsole.webcentral.au/