CDN Caching and Optimizations

After adding hostnames to your project, it's possible to configure Content Delivery Network (CDN) Caching. This can be done for all or specific hostnames within your project.

These caching options all relate to the traffic that goes through your hostname from the origin (Umbraco Cloud) to the end-user i.e. the traffic of your website and assets from the webserver to the browser.

The options that are currently available are:

  • Enable Cache (default: On)

  • Cache TTL (default: 120 minutes)

  • Cache Everything (default: off)

When a new hostname is added to a Project, the default settings will be applied. However, you can change the default settings for your project, so that the new hostnames will get the settings you have chosen. This also means that if you enable caching in the default settings and add a new hostname, that caching will be enabled for that new hostname.

Caching Explained

When Caching is enabled on your project it means that static assets like CSS and images are going to be cached in the Content Delivery Network (CDN) used by Umbraco Cloud. How assets are cached is up to you, as you can control it through 'cache-control headers'.

By default, Umbraco Cloud will enforce a minimum Time to Live (TTL) based on the Plan of your Umbraco Cloud Project, which means that assets cannot be cached for a shorter period than what your Plan allows. You can always choose a longer duration, especially, if you don't expect your assets to change.

These files types are cached as static assets through the CDN: '7z', 'csv', 'gif', 'midi', 'png', 'tif', 'zip', 'avi', 'doc', 'gz', 'mkv', 'ppt', 'tiff', 'zst', 'avif', 'docx', 'ico', 'mp3', 'pptx', 'ttf', 'apk', 'dmg', 'iso', 'mp4', 'ps', 'webm', 'bin', 'ejs', 'jar', 'ogg', 'rar', 'webp', 'bmp', 'eot', 'jpg', 'otf', 'svg', 'woff', 'bz2', 'eps', 'jpeg', 'pdf', 'svgz', 'woff2', 'class', 'exe', 'js', 'pict', 'swf', 'xls', 'css', 'flac', 'mid', 'pls', 'tar', 'xlsx'.

If you want to disable caching on certain types of static assets, you can use a 'no-cache' cache-control header, which will be respected by the caching strategy in the CDN. You can utilize an outbound rewrite rule to add such a cache-control header to the request.

The following example adds a cache-control header with 'no-cache' as the value when the requested Url contains a PDF file:

        <rule name="Set Cache-Control - No-Cache PDF">
            <match serverVariable="RESPONSE_Cache_Control" pattern=".*" />
                <add input="{REQUEST_URI}" pattern="\.(pdf)$" />
            <action type="Rewrite" value="no-cache"/>

The webpage itself is not cached when CDN Caching is enabled.

Cache Everything

When Cache Everything is enabled, everything including the webpage is cached in the CDN. So, in addition to static assets, the webpage will also be cached and served from the CDN instead of loading from the origin.

When a webpage is cached, it will be stripped of any cookies that are otherwise part of the request. If you use cookies as part of the website, be aware of the implications of using Cache Everything.

When using Cache Everything you should use a Cache TTL, which matches the Editor's expectations of when the webpage is refreshed with a new version loaded from the origin. As an example, choosing a Cache TTL of 2 hours means that the webpage will be served from the cache for 2 hours and then it will be refreshed with a copy from the origin. If Editors make changes every 30 minutes, they will have to wait at least two hours until they can see the changes on the website.

We recommend using Cache Everything with caution.

Purge Caching

When assets are cached for a long time and you need to refresh them, you can choose to purge the CDN cache to remove everything from the cache and force a refresh. This can be useful after having deployed changes to JS and CSS files, which are cached in the CDN. If you have caching enabled, you can purge the cache in the Purge Cache section at the bottom of the page.

Cache purging is done per hostname and it can take up to 30 seconds before assets are completely gone from the CDN, as it's refreshed globally.

By default, all hostnames are selected, but you can choose to purge specific hostnames from the environments in your Umbraco Cloud project.

Purging the cache is a heavy operation, so there is a constraint on how many purge requests can be done within 24 hours. The 24 hours starts from the moment you Purge. So if you have 2 Purge requests available and Purge twice within an hour, then you can Purge again in 23 hours (for the first Purge request) and then again in 24 hours (for the second Purge request).

In the Purge Cache section, you can see how many Purge requests you have available and when.

The available number of Purge requests varies depending on your Cloud Plan. For more information, see the Plan specific features.

Plan specific features

Access to the different options varies depending on the Umbraco Cloud Plan your project is on. Currently, the features available are as follows:

  • Starter:

    • Enable Cache

    • Cache TTL (see below for minimum TTL)

  • Standard:

    • Enable Cache

    • Cache TTL (see below for minimum TTL)

    • Cache Everything

  • Professional:

    • Enable Cache

    • Cache TTL (see below for minimum TTL)

    • Cache Everything

The minimum Cache TTL varies as follows:

  • Starter: 2 hours/120 minutes

  • Standard: 30 minutes

  • Professional: 2 minutes

The number of Cache Purge requests within 24 hours:

  • Starter: 2

  • Standard: 10

  • Professional: 20

CDN Caching and Optimizations

From your Umbraco Cloud Project, click CDN Caching & Optimization from the Settings dropdown to configure the caching options. All settings are scoped per environment, so if you have multiple environments and add your hostnames to different environments you can select the environment at the top of the page.

Aside from environments, the CDN Caching & Optimization page is divided into two parts: Default Settings and Hostname Specific Settings.

Use the Default settings to configure default settings that should be applied to new and existing hostnames.

If you want to have different caching options for different hostnames, then select the hostname under Hostname-specific settings and adjust the options for that specific hostname. This might be useful if you want to test the different options on another hostname than your primary hostname.

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