> ## Documentation Index
> Fetch the complete documentation index at: https://docs.preprod.world/llms.txt
> Use this file to discover all available pages before exploring further.

# Integrate a CDN resource with Concrete CMS

The Use CDN add-on integrates Concrete CMS 9.0.0 and later with a pull-based Gcore CDN resource. It rewrites static asset URLs in rendered HTML so visitors load them through the resource's custom domain.

<Warning>
  Back up site files and the database before making changes.

  The add-on rewrites rendered HTML with regular expressions, which may break HTML and increase time to first byte. It does not process dynamically loaded content or absolute references inside CSS, JavaScript, and HTML files.

  Disable the add-on if rewritten pages or assets fail to load correctly.
</Warning>

Create a [CDN resource](/cdn/getting-started/create-a-cdn-resource/create-a-cdn-resource) with the Concrete CMS website as its origin because the add-on supports only pull-based CDN configurations. Configure a [custom domain](/cdn/cdn-resource-options/general/create-and-set-a-custom-domain-for-the-content-delivery-via-cdn), verify its CNAME record points to Gcore, and confirm that the domain has a valid SSL certificate.

<Steps>
  <Step title="Install the add-on">
    Install the [Use CDN](https://market.concretecms.com/products/use-cdn/81cb661d-2dd1-11ef-951f-0a97d4ce16b9) add-on from the Concrete CMS Marketplace.
  </Step>

  <Step title="Open CDN Settings">
    In the Concrete CMS dashboard:

    1. Select **System & Settings**.
    2. Select **Optimization**.
    3. Select **CDN Settings**.
  </Step>

  <Step title="Enter the custom domain">
    Enter the custom domain configured for the CDN resource in the [Gcore Customer Portal](https://portal.gcore.com/cdn/resources/list). A custom domain typically looks like `cdn.site.com`.
  </Step>

  <Step title="Apply the changes">
    Save the settings.
  </Step>

  <Step title="Confirm the integration">
    The add-on rewrites URLs only for visitors who are not logged in as administrators:

    1. Log out of Concrete CMS or open the website in an incognito window.
    2. Open the browser developer tools with <kbd>F12</kbd>.
    3. Select the **Network** tab.
    4. Refresh the page.
    5. Confirm that static files load from the custom domain instead of the original domain.
  </Step>
</Steps>