Custom Domain Changes

Replacing or removing a Primary Custom Domain affects the addresses people and systems use to reach your site. Plan the transition around existing links, authentication, DNS, and partner allowlists. Additional Custom Domains keep their own certificates and DNS records, so a change to the primary address does not remove those domains.

For a transition in which old and new addresses must coexist, consider multiple domains before making a direct switch. Domains sharing a valid SAN certificate can remain alternate entry points while you change which one is primary. New Share Links, Inbox URLs, and emailed links use the selected Primary Custom Domain; old links continue to work only while their hostname remains configured, covered by a valid certificate, and correctly routed.

Changing the Files.com-provided address is a separate Custom Subdomain change.

Authentication and Connection Effects

Yubikey, WebAuthn, and FIDO two-factor authentication methods are tied to the login domain. Changing or removing the Primary Custom Domain removes those registrations and requires affected users to register again. Files.com warns you when users will be affected. Review the domain and 2FA guidance before the transition.

SSO settings also need to identify a hostname that remains associated with your site. If the IdP's Relay State names the Files.com subdomain, changing the Custom Domain does not affect that identifier. If it names a Custom Domain you retire, IdP-initiated logins fail until it is updated. SP-initiated logins are not affected by that Relay State change.

Changing a Primary Custom Domain retains an enabled custom username namespace. Removing it has stricter requirements, described below. A replacement also needs its DNS and dedicated addresses maintained through the transition so existing network rules continue to work.

Preparation for Switching Custom Domain

Schedule a direct switch for a period of minimal usage. It can have a transition of about 5–15 minutes when the old domain is not guaranteed to work and the new one is not complete. Certificate issuance and the time needed for servers to present the new certificate contribute to that interruption.

Set the custom domain's CNAME TTL to the lowest value your DNS provider allows, usually 60 seconds. Make that change 2–3 days ahead where possible, allowing old cached DNS records to expire before the switch. Files.com recommends keeping the TTL low afterward because the small DNS performance benefit of a larger value does not outweigh the longer time needed for future changes.

If you provide your own certificate, upload the new certificate before the change. With a Files.com-managed certificate, Files.com generates the certificate when you change the domain.

Switching Your Custom Domain

Create the new domain's CNAME record. For a Files.com-managed primary certificate, it points at your Files.com subdomain. For your own certificate, use the exact target displayed for that domain under DNS Configuration in the SSL Certificates settings.

Once the new record resolves, update the Primary Custom Domain setting in Files.com. If you supply your own certificate, activate it after updating the domain setting. Newly generated links and emails use the new primary address. Update client configurations and integrations that should now connect through it.

Complete the replacement setting and correct DNS configuration within five days of removing the old setting to retain the Primary Custom Domain's dedicated addresses. Otherwise those addresses are released. Dedicated IP Addresses explains the allocation and release rules, including addresses assigned separately to additional domains.

Removing Your Custom Domain

An enabled SSO integration must be disabled before the Primary Custom Domain can be removed. Change the authentication method for every user associated with the SSO provider, then disable the integration.

Removal also ends the site's custom username namespace. Usernames must be globally unique across Files.com sites. If any are already used elsewhere, Files.com blocks removal and identifies the users who must be renamed or removed first. Review username namespaces before retiring the domain.

Before removal, move users and integrations to the Files.com subdomain and confirm their network rules permit its addresses and required service destinations. Removing the Primary Custom Domain immediately prevents connections through that hostname. If you are administering the site through it, reconnect using the Files.com subdomain.

The Primary Custom Domain's dedicated addresses are released after five days. Additional domains retain their own addresses and certificates. The Files.com subdomain then resolves to the general pool, so a network that allowed only the old dedicated pair needs its rules updated.