---
title: Add custom domains for library assets
slug: content-marketing-platform/docs/add-custom-domains-for-library-assets
docTags: 
createdAt: 2026-07-20T15:44:21.897Z
---

You can share assets from the library with a public link. You can customize the URL by which you share your files. By default, the system-generated file URLs have the following format. You can update it to any URL the clients want using the custom domain integration.

`<random_6_character_prefix>.files.welcomesoftware.com`

For example, the default URL for *My Organization* would be `ksheut.files.welcomesoftware.com`, but you can integrate `files.myorganization.com` instead. So, after the custom domain integration, the URL looks like `files.myorganization.com/download/<unique_file_guid>`.

## Prerequisites

Confirm that your domain meets these requirements before you add it. Some requirements affect whether Optimizely can issue and renew the HTTPS certificate for your domain.

- **Fully qualified subdomain** – Use a subdomain such as `files.org.com`. You cannot use top-level domains such as `org.com`.
- **Unique domain** – You must have a unique domain. You cannot save a domain that another organization already uses.
- **One domain per resource type** – A custom domain works for only one resource type. You cannot use the same domain for both Library assets and Collections. Each resource type requires its own domain.
- **Certification Authority Authorization (CAA) records** – If your domain uses CAA records, they restrict which certificate authorities can issue certificates. In that case, add a CAA record for `pki.goog` to authorize Google Trust Services. Optimizely issues custom domain certificates through Cloudflare using Google Trust Services. A CAA record that omits `pki.goog` blocks the initial certificate issuance and future automatic renewals. CAA records set on a parent domain, such as `org.com`, also apply to its subdomains, such as `files.org.com`.

## Add the domain

1. Go to your avatar > **Organization** > **Custom Domain**.
2. Click **Add New**. The **Add New Custom Domain** dialog box displays.

::Image[]{src="https://api.archbee.com/api/optimize/BrbvVORKJ5iIeSMZye5kI/UJTlCx7N3tz2J_drJM2QG_add-custom-domain.png" size="100" isUploading="false" width="676" height="389" darkWidth="676" darkHeight="389" showCaption="false" indent="1"}

3. Select the domain type, enter the domain, and click **Save**. The domain displays in the list.
4. Create the DNS record displayed in the table in your domain's DNS provider. 
   Propagation can take up to 24 hours. If you need help, contact the development team that manages your organization's domain.
5. Click **Check Status** to verify whether the record propagated. If the record is not verified, an error message asks you to try again later. When the record propagates, **Verified** replaces **Check Status**.

::Image[]{src="https://api.archbee.com/api/optimize/BrbvVORKJ5iIeSMZye5kI/nhHkv6uPr-Ts3QYwTvaMx_add-custom-domain-2.png" size="100" isUploading="false" width="662" height="448" darkWidth="662" darkHeight="448" showCaption="false" indent="1"}

To export the records, open the options menu (**...**) and select **Download as CSV**.

## Activate the domain

Click **Activate** to use the domain as your default domain for library files.

![](https://api.archbee.com/api/optimize/BrbvVORKJ5iIeSMZye5kI/QnzD4MyX6iWqjE5cqQLWB_activate-the-domain.png)

When the domain is activated a message and **Activated** label displays.

![](https://api.archbee.com/api/optimize/BrbvVORKJ5iIeSMZye5kI/qYmIqoNMDP8WpTzkpd32__activate-the-domain-organization.png)

After successful activation, CMP uses the custom domain as the public link for the library files.

![](https://api.archbee.com/api/optimize/BrbvVORKJ5iIeSMZye5kI/DK5ViME3bJMvxpqBXiyIy_public-link.png)

## Delete a domain

Click **Delete** (trash can icon) next to a domain to delete it. After you delete a custom domain, CMP uses the default system-generated URL as the public link for files.

## Troubleshooting

If assets load over HTTP but fail over HTTPS, the problem is usually certificate issuance rather than domain configuration. Verify your CAA records (see [Prerequisites](docId\:gJWjNJGZmcipJ3FiR-yAf)) before you remove and re-add the custom domain. Removing the domain does not trigger certificate reissuance.