Every site includes a unique custom subdomain of the files.com domain, and site administrators can change this subdomain at any time. When changing your subdomain, you can optionally preserve the old one so that traffic to it automatically redirects to your new address and the old name remains associated with your site.

Your site's custom subdomain is not impacted by your site's custom domain. Adding, changing or removing a custom domain for your site does not prevent you from using your site's custom subdomain.

Custom Domain Versus Custom Subdomain

There are several differences between your site's custom subdomain and a custom domain.

The custom subdomain for your site is a unique subdomain of the files.com domain, in the form of <your-subdomain>.files.com. It will always end in .files.com. A custom domain is an address that you define on any domain that you control.

Every Files.com site has its own unique custom subdomain. Configuring a custom domain is optional (and easy), and many sites do not have a custom domain.

Files.com always manages the SSL certificates for your custom subdomain address. Files.com can also provide and manage SSL certificates for a custom domain address, but you have the option of providing your own SSL certificates for the custom domain.

Files.com manages the CNAME DNS records for your custom subdomain address, but you are responsible for the CNAME DNS records for a custom domain.

Subdomain Availability

An available subdomain can be claimed by any Files.com site. Names reserved by Files.com, names currently assigned to another site, and names held as preserved subdomains are unavailable, with the expired-trial exception below.

Changing your subdomain without preserving the old one releases the old name as soon as the change is saved. There is no grace period, reservation, or priority for the former holder. Another Files.com site can immediately claim it, so the old address can lead to another customer's site. Preserve the old subdomain while users and integrations still rely on it, and update those connections before releasing it. Customer Isolation explains the distinction between reusing an address and accessing the original site's data.

Expired Trial Sites

A paid site can claim a subdomain currently assigned to an expired trial site. Files.com automatically gives the expired trial a different subdomain and records the change in that site's Settings Changes log. This keeps an expired trial from reserving a name indefinitely when a paying customer wants to use it.

This exception does not apply to an unexpired trial, a paid site's current subdomain, or a preserved subdomain. An expired trial's administrator does not need to rename the trial before a paid site can claim its name.

Changing Your Subdomain if You Also Have a Custom Domain

Before making this change, we recommend enabling the Preserve the old subdomain option. While DNS propagates and your users and integrations adjust to the new subdomain, the redirect makes sure that anyone still hitting your old Files.com subdomain continues to reach your site without interruption.

A custom domain is tied to your site's custom subdomain via the DNS records used to link your custom domain. If you want to change your custom subdomain, you might experience a brief transition period due to the DNS propagation needed to effect the change, and you will also need to make changes to your custom domain's DNS records to reflect the change.

This transition time is caused by 3 things: re-registering your SSL certificate (if we are registering it), a time delay where some of our edge servers will serve your old subdomain's certificate and others will serve your new subdomain's certificate, and the need to create DNS records in the Files.com DNS for your new subdomain.

We recommend you plan the switch for a time period where your site has minimal usage, such as a night or weekend.

If you are planning on changing both your custom subdomain and domain, we recommend doing these events on separate days to reduce the risks and make rollback easier.

Before You Switch Your Subdomain

To minimize downtime, plan ahead and review the steps before making the change. Lower the TTL values on your DNS records, wait for propagation, change your subdomain, update the DNS values to point at the new subdomain, and wait for the changes to take effect.

Update the Time To Live (TTL) values on the existing DNS records for your custom domain to a low value, such as 60 seconds. This will tell DNS servers across the internet to prepare for a change in the destination of this domain. This step needs to be performed ahead of time, ideally 2-3 days ahead of time, to allow the maximum impact.

Switching Your Subdomain

When ready to switch, update your subdomain setting in Files.com. Then update the DNS records for your custom domain to use your new subdomain in the files.com CNAME part of the record.

Wait for the changes to take effect.

While you could choose to increase your TTL values from 60 seconds at this point, we strongly recommend setting the value as low as your provider will allow.

If you are using dedicated IP addresses, you'll need to complete the process and update your DNS entries within 5 days to keep the same dedicated IP addresses. If the DNS entries for your custom domain are not set up properly within that 5-day period, your dedicated IPs will be released to be used by other customers.

Changing Your Subdomain if You Do Not Have a Custom Domain

Before making this change, we recommend enabling the Preserve the old subdomain option. Unlike a custom domain change, there is no DNS propagation window to act as a buffer. Instead, the old subdomain is released immediately unless you preserve it, and another site can claim it. Enabling preservation ensures your users, existing links, and any integrations pointing at the old subdomain continue to work without interruption.

You can change your custom subdomain, which will change the URLs used to access your Files.com site. When you change your custom subdomain, you will be logged out and returned to the new subdomain login page to log in again.

Unless you choose to preserve your old subdomain, your users must start using the new subdomain URL for all connections to your Files.com site immediately, because the old subdomain will no longer point to your site.

When the custom subdomain is changed, any existing Share Links, Inboxes, and Publicly Hosted folders will now use your new subdomain in their link URLs. This doesn't apply to a publicly hosted folder bound to its own Additional Custom Domain; that folder's link stays on its own domain and isn't affected by a subdomain change. Unless you preserve your old subdomain, links that have been bookmarked or shared with others will no longer lead to your site and may lead to another site if it claims the old subdomain.

Email notifications that were sent prior to the change will contain links with the old subdomain. Unless you preserve your old subdomain, you will need to give recipients updated links, because the old address is available for another site to claim. New email notifications will contain updated links that use your new custom subdomain.

If you have embedded your old subdomain URL into any scripts, programs, or system configurations, then you'll also need to update those to point to your new subdomain. This includes any use of our SDKs or APIs. If you preserve your old subdomain, those connections will continue to work via redirect, but we recommend updating them to use the new subdomain.

Preserving Your Old Subdomain

When you change your subdomain, you can preserve the old one so that traffic to it automatically redirects to your new address. Preservation also prevents another site from claiming the old name. This is useful during rebrands, mergers, or other organizational changes where your users have existing bookmarks, saved links, or scripts pointing at the old subdomain.

This feature applies only to Files.com subdomains (addresses ending in .files.com). It does not apply to custom domains.

When you enter a new subdomain, select Preserve old subdomain and automatically redirect traffic to preserve it when the change is saved. Preservation is optional for each rename; preserving a name during an earlier change does not automatically preserve the next name you replace.

For a rename through the Site API, include redirect_old_subdomain: true with the new subdomain in the same PATCH /site request. This parameter requests preservation for that change; it is not a persistent setting returned by GET /site.

Managing Preserved Subdomains

Migrated Subdomains shows every preserved subdomain along with its creation date. API clients can check preserved names with GET /site_subdomain_redirects.

A preserved name cannot be chosen as a current subdomain by any site, including the site that preserved it. To change your site back to that name, you must first delete its preservation. Deleting it stops the redirect and immediately releases the name for any Files.com site to claim, with no grace period or priority for you. Update users and integrations before deleting a preserved subdomain.

Redirects for preserved subdomains do not expire automatically. They remain active until you delete them.

Creation Limits

You can create one preserved subdomain every 60 days. Deleting a preserved subdomain does not reset this window, so plan your subdomain changes accordingly.

Changing Your Subdomain with Active SSO Integrations

Changing your subdomain does not affect SP-initiated logins. IdP-initiated logins depend on the Relay State field in your IdP, which the provider setup instructions tell you to set to your Files.com subdomain.

If you preserve your old subdomain, the old subdomain remains one of your site's hostnames and no IdP change is needed. If you do not preserve it, IdP-initiated logins fail from the moment the change takes effect until you update the field to your new subdomain or to your custom domain.